MALITH DAVD MALUK A56/83099/2015 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN PLANT BREEDING AND BIOTECHNOLOGY DEPARTMENT OF PLANT SCIENCE AND CROP PROTECTION FACULTY OF AGRICULTURE UNIVERSITY OF NAIROBI 2018 DECLARATION I declare that this thesis is my original work and has not been presented for any award of degree in any other University

MALITH DAVD MALUK A56/83099/2015 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN PLANT BREEDING AND BIOTECHNOLOGY DEPARTMENT OF PLANT SCIENCE AND CROP PROTECTION FACULTY OF AGRICULTURE UNIVERSITY OF NAIROBI 2018 DECLARATION I declare that this thesis is my original work and has not been presented for any award of degree in any other University. Malith David Maluk Date . The thesis is submitted for examination with our approval as the University supervisors Prof. Kahiu Ngugi …. Date …… Department of Plant Science and Crop Protection, University of Nairobi Prof. Florence Olubayo.. Date . Department of Plant Science and Crop Protection, University of Nairobi Dr. Eric Manyasa ……. Date ……… International Crop Research Institute for the Semi-Arid Tropics (ICRISAT) DEDICATION I dedicate this thesis to my family. First of all to my beloved wife,Philis Mutoro whose contribution led to the writing and compilation of this research thesis. To my son Morgan Ayak, who had been waking me up to take to the table and write the thesis. May God bless them all. ACKNOWLEDGEMENT I am greatly indebted to almighty God for keeping me upright from the innception to the end of this project. My sincere thanks and gratitudee to the Alliance for a Green Revolution in Africa (AGRA) through partners for seeds in Africa (PASA) and the University of Nairobi for financial supoort without which I could not have finished this study. My sincere gratitudes to Prof Kahiu Ngugi, Prof Olubayo and Dr Eric Manyasa for guiding me throughout the course of this study. My sincere appreciation goes to AGRA project coordinators and AGRA staff especially, Prof. Florence Olubayo, Prof. James Muthomi, Dr Felister Nzuve, Dr Jane Ininda and Dr Newton Ochanda for taking good care of me at my hospital bed while nursing fractures, wounds and all the bruises i sustained from the accident. Lastly but not least, a huge thank you to my family, especially my wife Philis Mutoro for keenly looking at me when I had an accident and throughtout the course of my studies. May God bless her and my Son Morgan. TOC o 1-3 h z u HYPERLINK l _Toc514776254 DECLARATION PAGEREF _Toc514776254 h ii HYPERLINK l _Toc514776255 DEDICATION PAGEREF _Toc514776255 h iii HYPERLINK l _Toc514776256 ACKNOWLEDGEMENT PAGEREF _Toc514776256 h iv HYPERLINK l _Toc514776257 ABSTRACT PAGEREF _Toc514776257 h viii HYPERLINK l _Toc514776258 CHAPTER ONE PAGEREF _Toc514776258 h 1 HYPERLINK l _Toc514776259 INTRODUCTON PAGEREF _Toc514776259 h 1 HYPERLINK l _Toc514776260 CHAPTER TWO PAGEREF _Toc514776260 h 5 HYPERLINK l _Toc514776261 LITERATURE REVIEW PAGEREF _Toc514776261 h 5 HYPERLINK l _Toc514776262 2.1 Sorghum (Sorghum Bicolor (L) Moench) PAGEREF _Toc514776262 h 5 HYPERLINK l _Toc514776263 2.2 Origin and distribution of sorghum PAGEREF _Toc514776263 h 5 HYPERLINK l _Toc514776264 2.3 Constraints to sorghum production in East Africa PAGEREF _Toc514776264 h 6 HYPERLINK l _Toc514776265 2.4 Effects of drought stress on plant development and productivity PAGEREF _Toc514776265 h 6 HYPERLINK l _Toc514776266 2.5 Sorghum drought tolerance mechanisms. PAGEREF _Toc514776266 h 8 HYPERLINK l _Toc514776267 2.5.1 Drought escape PAGEREF _Toc514776267 h 8 HYPERLINK l _Toc514776268 2.5.2 Drought avoidance PAGEREF _Toc514776268 h 8 HYPERLINK l _Toc514776269 2.5.3 Drought recovery PAGEREF _Toc514776269 h 9 HYPERLINK l _Toc514776270 2.5.4 Drought tolerance PAGEREF _Toc514776270 h 9 HYPERLINK l _Toc514776271 2.6 Drought tolerance mechanisms of staygreen genotypes PAGEREF _Toc514776271 h 12 HYPERLINK l _Toc514776272 2.6.1 Morphological adaptations. PAGEREF _Toc514776272 h 12 HYPERLINK l _Toc514776273 2.6.2 Physiological defense mechanism PAGEREF _Toc514776273 h 13 HYPERLINK l _Toc514776274 2.6.3 Biochemical defense Mechanisms PAGEREF _Toc514776274 h 15 HYPERLINK l _Toc514776275 2.6.4 Hormonal defense mechanisms PAGEREF _Toc514776275 h 16 HYPERLINK l _Toc514776276 2.7 Mating design PAGEREF _Toc514776276 h 16 HYPERLINK l _Toc514776277 2.7.1 Combining ability PAGEREF _Toc514776277 h 17 HYPERLINK l _Toc514776278 SCREENING SORGHUM GENOTYPES FOR DROUGHT TOLERANCE, EARLINESS AND HIGH YIELD PAGEREF _Toc514776278 h 19 HYPERLINK l _Toc514776279 3.1 Introduction PAGEREF _Toc514776279 h 19 HYPERLINK l _Toc514776280 3.2 Materials and methods PAGEREF _Toc514776280 h 21 HYPERLINK l _Toc514776281 3.2.1 Description of site of study PAGEREF _Toc514776281 h 21 HYPERLINK l _Toc514776282 3.2.2 Germplasm PAGEREF _Toc514776282 h 21 HYPERLINK l _Toc514776283 3.2.3 Experimental design and layout PAGEREF _Toc514776283 h 23 HYPERLINK l _Toc514776284 3.2.4 Data collection PAGEREF _Toc514776284 h 24 HYPERLINK l _Toc514776285 3.2.5 Data analysis PAGEREF _Toc514776285 h 26 HYPERLINK l _Toc514776286 3.3 Results PAGEREF _Toc514776286 h 27 HYPERLINK l _Toc514776287 3.3.1 Characterization of the morphological traits for the different sorghum genotypes PAGEREF _Toc514776287 h 27 HYPERLINK l _Toc514776288 3.3.2 Assessment of phenology and yield components of South Sudan Sorghum germplasm PAGEREF _Toc514776288 h 37 HYPERLINK l _Toc514776289 3.6 Discussions PAGEREF _Toc514776289 h 61 HYPERLINK l _Toc514776290 3.6.1 Morphological characters PAGEREF _Toc514776290 h 61 HYPERLINK l _Toc514776291 3.6.2 Physiological characters PAGEREF _Toc514776291 h 63 HYPERLINK l _Toc514776292 3.6.3 Assessment of earliness in South Sudan sorghum germplasm PAGEREF _Toc514776292 h 64 HYPERLINK l _Toc514776293 3.6.4 Assessment of yield in South Sudan sorghum germplasm PAGEREF _Toc514776293 h 65 HYPERLINK l _Toc514776294 3.6.5 Yield components PAGEREF _Toc514776294 h 66 HYPERLINK l _Toc514776295 CHAPTER FOUR PAGEREF _Toc514776295 h 68 HYPERLINK l _Toc514776296 COMBINING ABILITY FOR EARLINESS, YIELD AND DROUGHT TOLERANCE AMONG F1 SORGHUM GENOTYPES PAGEREF _Toc514776296 h 68 HYPERLINK l _Toc514776297 4.1 Introduction. PAGEREF _Toc514776297 h 68 HYPERLINK l _Toc514776298 4.2 Materials and methods PAGEREF _Toc514776298 h 70 HYPERLINK l _Toc514776299 4.2.1 Site description PAGEREF _Toc514776299 h 70 HYPERLINK l _Toc514776300 4.2.2 Germplasm PAGEREF _Toc514776300 h 71 HYPERLINK l _Toc514776301 4.2.3 Experimental design PAGEREF _Toc514776301 h 71 HYPERLINK l _Toc514776302 4.2.4 Data collection PAGEREF _Toc514776302 h 71 HYPERLINK l _Toc514776303 4.2.5 Data analysis PAGEREF _Toc514776303 h 72 HYPERLINK l _Toc514776304 4.3 Results PAGEREF _Toc514776304 h 72 HYPERLINK l _Toc514776305 4.3.1 Analysis of variance for the different traits among the sorghum genotypes PAGEREF _Toc514776305 h 72 HYPERLINK l _Toc514776306 4.3.2 Mean performance of the single cross sorghum hybrids PAGEREF _Toc514776306 h 72 HYPERLINK l _Toc514776307 4.3.3 General combining ability estimates among the sorghum genotypes PAGEREF _Toc514776307 h 72 HYPERLINK l _Toc514776308 4.3.4 Specific combining ability effects among the sorghum hybrids PAGEREF _Toc514776308 h 72 HYPERLINK l _Toc514776309 4.4 Discussions PAGEREF _Toc514776309 h 72 HYPERLINK l _Toc514776310 4.4.1 General combining ability estimates among the sorghum genotypes PAGEREF _Toc514776310 h 72 HYPERLINK l _Toc514776311 4.4.2 Estimates of specific combining ability effects among the sorghum hybrids PAGEREF _Toc514776311 h 72 HYPERLINK l _Toc514776312 4.4.3 Reciprocal combining effects among the sorghum hybrids PAGEREF _Toc514776312 h 72 HYPERLINK l _Toc514776313 CHAPTER FIVE PAGEREF _Toc514776313 h 72 HYPERLINK l _Toc514776314 GENERAL DISCUSSION, CONCLUSION AND RECOMMENDATION PAGEREF _Toc514776314 h 72 HYPERLINK l _Toc514776315 5.1 GENERAL DISCUSSION AND CONCLUSION PAGEREF _Toc514776315 h 72 HYPERLINK l _Toc514776316 5.2 RECOMMENDATIONS PAGEREF _Toc514776316 h 72 LIST OF TABLES TOC h z t Caption c HYPERLINK l _Toc514776317 Table 3. 1. South Sudan sorghum germplasm and ICRISAT-Nairobi elite lines. PAGEREF _Toc514776317 h 22 HYPERLINK l _Toc514776318 Table 3.2. Means squares of morphological characters under well irrigated and drought stressed environments PAGEREF _Toc514776318 h 27 HYPERLINK l _Toc514776319 Table 3.3. Performance of South Sudan and ICRISAT sorghum germplasm under drought stress condition PAGEREF _Toc514776319 h 29 HYPERLINK l _Toc514776320 Table 3.4 Morphological characters for drought stress tolerance of South Sudan and ICRISAT sorghum germplasm PAGEREF _Toc514776320 h 33 HYPERLINK l _Toc514776321 Table 3.4. Means square of growth components of South Sudan and ICRISAT sorghum germplasm under well irrigated and drought stress conditions PAGEREF _Toc514776321 h 37 HYPERLINK l _Toc514776322 Table 3.5. Effect of water stress on growth characters of South Sudan and ICRISAT sorghum germplasm PAGEREF _Toc514776322 h 38 HYPERLINK l _Toc514776323 Table 3.5. Comparison of growth response of South Sudan and ICRISAT sorghum germplasm under well irrigated and water stress conditions. PAGEREF _Toc514776323 h 42 HYPERLINK l _Toc514776324 Table 3.6 Means square of phenology and yield components of South Sudan and ICRISAT sorghum germplasm, PAGEREF _Toc514776324 h 46 HYPERLINK l _Toc514776325 Table 3.7 Effect of water stress on phenology and yield characters of South Sudan and ICRISAT sorghum germplasm PAGEREF _Toc514776325 h 48 HYPERLINK l _Toc514776326 Table 3.8 Phenological and yield response of South Sudan and ICRISAT sorghum germplasm under well irrigated and drought stress conditions PAGEREF _Toc514776326 h 53 HYPERLINK l _Toc514776327 Table 3.9 Correlation coefficients among the different traits under water stress condition PAGEREF _Toc514776327 h 59 HYPERLINK l _Toc514776328 Table 3.10 Correlation coefficients among the different traits under well irrigated condition PAGEREF _Toc514776328 h 60 HYPERLINK l _Toc514776329 Table 4.1. Parental lines intercrossed in a 6 x 6 full diallel mating design PAGEREF _Toc514776329 h 71 HYPERLINK l _Toc514776330 Table 4.1 Means square for all the traits studied under drought stress conditions PAGEREF _Toc514776330 h 72 HYPERLINK l _Toc514776331 Table 4.2 Means performance of F1 crosses between South Sudan farmers preferred lines and exotic lines PAGEREF _Toc514776331 h 72 HYPERLINK l _Toc514776332 Table 4.3 Estimate of GCA among sorghum genotypes PAGEREF _Toc514776332 h 72 HYPERLINK l _Toc514776333 Table 4.4 Estimate of SCA among the sorghum hybrids PAGEREF _Toc514776333 h 72 HYPERLINK l _Toc514776334 Table 4.5 Estimate of reciprocal combining ability (RCA) effects among sorghum genotypes PAGEREF _Toc514776334 h 72 ABSTRACT Sorghum production is highly constraint by water stress in sub Saharan Africa. The current study aimed to identify good combiners for earliness and yield under drought stress condition to develop superior sorghum hybrids for improved food and nutritional security in drought prone areas of South Sudan. Genotypes and water regimes had effects on staygreen score, dry leaf scores, waxy bloom, leaf area, leaf rolling, total leaf count and lodging implying genetic diversity for the sorghum genotypes evaluated in this study. The correlation coefficient revealed that staygreen was positively correlated with panicle weight, grain yield, 100-seed weight and harvesting index suggesting that these traits could be used to select for drought tolerant sorghum genotypes. The sorghum genotypes Olerere (12.82) exhibiting the lowest DLS while Omuhathi (76.23) showed the highest senescence. Reduced total leaf counts and net leaf area were observed among improved staygreen lines namely IESV92028DL IESV91111DL, Mahube, IESV92172DL, Gwada and IESV23010DL. The sorghum genotypes with staygreen traits minimize water use during the pre-anthesis phase so as to conserve water for grain filling during the grain development phase leading to high yields. The accessions that scored dense wax load under drought stress condition were Gwada, ICSR161, Mahube, AG8, IESV91131DL, IESV91111DL, IESV92028DL and IESV92172DL and comprised of lines drawn from ICRISAT- Nairobi gene bank. Dense wax load under drought stress condition has been associated with cuticular wax biosynthesis translocation, composition and density and are influenced solely by environmental factors including solar radiation, temperature, moisture, and humidity in sorghum. The superior lines that outperformed the check variety for earliness were Wotecollection1 (56.94days), IESV23010DL (58.06days, ZSV3 (60.09days), Bizany (61.17days) and Tabat (61.17days). However, there were yield penalties observed among the accessions wotecollection1, Bizany, ZSV3 and Tabat. Thus, the accessions IESV23010DL would best serve as an ideal drought evading candidate with better performance for grain yield. The genotypes Lobuheti (50.65g), IESV91131DL (46.52g), Lodoka1 (47.08g) and IESV92172DL (46.69g) showed superior field weights as opposed to the check variety. Among yield contributing components, harvesting index and threshability are considered key determinants of the final grain yield. Accession IESV91131DL and IESV92172DL recorded high harvesting index (3.13 and 6.86) and threshing percentage of 73.94 and 67.34. Results of correlation coefficient revealed that panicle weight showed positive correlation with grain yield, harvesting index, and panicle width suggesting that these traits could be used as the basis for selection for high grain yield in sorghum breeding programs. There were significant differences among the maternal and non-maternal effects implying that cytoplasmic genes play a great role in regulating maturity. There were larger mean squares of GCA than the SCA for days to flowering and panicle weight showing that additive genes play a bigger role than non additive genes in control of such traits. Negative significant general combining ability effects (GCA) were noted for days to flowering for parents ICSV111IN, B35 and Macia suggests that these parents had the earliness trait. The parents Lodoka, Okabir and Akuorachot with positive days to flowering implied lateness thus conferring the late physiological maturity. With regard to the panicle weight, the parental lines Macia, Okabir and Lodoka recorded positive GCA and high mean values for panicle weight. These parental lines are superior combiners for panicle weight. With regard to the combining ability for grain yield, the parents Macia, Lodoka, and ICSV111IN showed positive GCA effects implying they are good combiners for grain yield compared to parental lines B35, Okabir and Akuorachot which showed inferiority with regards to grain weight. For the 100-Seedweight, the parent Macia, Lodoka and ICSV111IN showed positive GCA suggesting that they are good combiners for that trait. Significant negative specific combining ability for days to flowering was exhibited by F1 cross, Okabir x Macia. In three out 15 F1 generation crosses, significant positive specific combining ability (SCA) effect for 100-seedweight was revealed in parent ICSV111IN x ICSV111IN, B35 x B35 and ICSV111IN x B35 suggesting that these crosses are superior combiners for 100 seed weight. Positive maternal effect for days to flowering was reported among the parents Lodoka, Macia and the cross Lodoka x Okabir. CHAPTER ONE INTRODUCTON Background Sorghum (Sorghum Bicolor L Moench) is the fifth food security cereal crop globally and the second most important staple cereal crop after maize in Africa and Asia ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract The difficulty of choosing appropriate selection environments has restricted breeding progress for drought tolerance in highly-variable target environments. Genotype-by-environment interactions in southern African maize-growing environments result from factors related to maximum temperature, seasonal rainfall, season length, within season drought, subsoil pH and socio-economic factors that result in sub-optimal input application. In 1997 CIMMYT initiated a product-oriented breeding program targeted at improving maize for the drought-prone mid-altitudes of southern Africa. Maize varieties were selected in Zimbabwe using simultaneous selection in three types of environments, (i) recommended agronomic management/high rainfall conditions, (ii) low N stress, and (iii) managed drought. Between 2000 and 2002, 41 hybrids from this approach were compared with 42 released and prereleased hybrids produced by private seed companies in 36-65 trials across eastern and southern Africa. Average trial yields ranged from less than 1 t/ha to above 10 t/ha. Hybrids from CIMMYTs stress breeding program showed a consistent advantage over private company check hybrids at all yield levels. Selection differentials were largest between 2 to 5 t/ha and they became less significant at higher yield levels. An Eberhart-Russell stability analysis estimated a 40 yield advantage at the 1-ton yield level which decreased to 2.5 at the 10-ton yield level. We conclude that including selection under carefully managed high priority abiotic stresses, including drought, in a breeding program and with adequate weighing can significantly increase maize yields in a highly variable drought-prone environment and particularly at lower yield levels. Media summary A new maize breeding approach shows significant yield increases in drought-prone environments in southern Africa. Introduction Even though the challenge of developing drought tolerant crop varieties has generated an immense amount of literature, most practical breeding efforts remain focused on increasing productivity under favorable conditions where genetic variance, heritability and therefore breeding progress for grain yield are greatest. Apart from adapting crop phenology to rainfall patterns, multi-environment trials (METs) including trials grown under random drought conditions are often the only systematic approach exploited to increase yield stability of new crop varieties in drought-prone environments (e.g. Fukai et al. 1999 Shaku2026, author dropping-particle , family Bu00e4nziger, given Marianne, non-dropping-particle , parse-names false, suffix , dropping-particle , family Setimela, given Peter S, non-dropping-particle , parse-names false, suffix , dropping-particle , family Hodson, given David, non-dropping-particle , parse-names false, suffix , dropping-particle , family Vivek, given Bindiganavile, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 0 , title Breeding for improved drought tolerance in maize adapted to southern Africa, type article-journal , uris http//www.mendeley.com/documents/uuid078d51e3-d742-3206-88f0-c05b9c5c3af1 , id ITEM-2, itemData DOI 10.1071/FP11101, ISBN 1445-4408, ISSN 14454408, abstract Drought resistance is being increasingly labelled as being a u2018complex traitu2019, especially with the recent expansion of research into its genomics. There is a danger that this labelmayturn into an axiom that is liable to damage education on the subject as well as research and the delivery of solutions to the farmer. This opinionated review examines whether there is grounds for such an axiom. Drought resistance is labelled as a u2018complex traitu2019 mainly when viewed by molecular biologists from the gene discovery platform. This platform is capable of expressing hundreds and thousands of drought-responsive genes, which are up- or down-regulated under dehydration stress according to growth stage, plant organ or even time of day. Sorting out the u2018grain out of the chaffu2019 in order to identify the function of the candidate genes towards drought resistance is difficult and, thus, the idea that drought resistance is complex is raised. However, when drought resistance is viewed from the physiological and agronomic whole-plant and crop platform, it appears much simpler its control, whether constitutive or adaptive, is rather obvious with respect to manipulation in breeding and crop management. The most important and common drought resistance traits function to maintain plant hydration under drought stress due to effective use of water (EUW). The state of our knowledge and the achievements in breeding for drought resistance do not support labelling drought resistance as a complex trait. Thegenomics road towards drought resistance is complex butwealreadyknowthat the destination is much simpler., author dropping-particle , family Blum, given Abraham, non-dropping-particle , parse-names false, suffix , container-title Functional Plant Biology, id ITEM-2, issue 10, issued date-parts 2011 , page 753-757, title Drought resistance is it really a complex trait, type article-journal, volume 38 , uris http//www.mendeley.com/documents/uuiddb34ce68-e6a1-4766-a98a-fb7f82791ba1 , mendeley formattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, n.d. Blum, 2011), manualFormatting (Blum, 2011), plainTextFormattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, n.d. Blum, 2011), previouslyFormattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, n.d. Blum, 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Blum, 2011). Farmers preference for sorghum comes from its ability to yield high in the face of severe abiotic and biotic stresses relative to crops such as maize (Zea mays), rice (Oryza sativa) and wheat (Triticum aestivum)ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/BGRES.0000024155.43149.71, ISSN 0925-9864, abstract Sorghum Sorghum bicolor (L.) Moench is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums., author dropping-particle , family C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, given G.C. Peterson, non-dropping-particle , parse-names false, suffix , dropping-particle , family 3, given 12, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given 4 4 5 D.T. Rosenow and G. Ejeta, non-dropping-particle , parse-names false, suffix , dropping-particle , family 51, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given , non-dropping-particle , parse-names false, suffix , container-title Genetic Resources and Crop Evolution, id ITEM-1, issue 5, issued date-parts 2004 , page 489-500, title Sorghums of the Sudan analysis of regional diversity and distribution, type article-journal, volume 51 , uris http//www.mendeley.com/documents/uuid70f9176c-f44b-4c18-84aa-e1266947bd44 , mendeley formattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, 3, , 51, 1, 2004), manualFormatting (Grenier et al., 2004), plainTextFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, 3, , 51, 1, 2004), previouslyFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, 3, , 51, 1, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Grenier et al., 2004). The importance of sorghum lies on its ability to withstand water stress as well as being a cheap source of carbohydrate, protein, fibre, vitamins to both human and animals ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1071/FP11101, ISBN 1445-4408, ISSN 14454408, abstract Drought resistance is being increasingly labelled as being a u2018complex traitu2019, especially with the recent expansion of research into its genomics. There is a danger that this labelmayturn into an axiom that is liable to damage education on the subject as well as research and the delivery of solutions to the farmer. This opinionated review examines whether there is grounds for such an axiom. Drought resistance is labelled as a u2018complex traitu2019 mainly when viewed by molecular biologists from the gene discovery platform. This platform is capable of expressing hundreds and thousands of drought-responsive genes, which are up- or down-regulated under dehydration stress according to growth stage, plant organ or even time of day. Sorting out the u2018grain out of the chaffu2019 in order to identify the function of the candidate genes towards drought resistance is difficult and, thus, the idea that drought resistance is complex is raised. However, when drought resistance is viewed from the physiological and agronomic whole-plant and crop platform, it appears much simpler its control, whether constitutive or adaptive, is rather obvious with respect to manipulation in breeding and crop management. The most important and common drought resistance traits function to maintain plant hydration under drought stress due to effective use of water (EUW). The state of our knowledge and the achievements in breeding for drought resistance do not support labelling drought resistance as a complex trait. Thegenomics road towards drought resistance is complex butwealreadyknowthat the destination is much simpler., author dropping-particle , family Blum, given Abraham, non-dropping-particle , parse-names false, suffix , container-title Functional Plant Biology, id ITEM-1, issue 10, issued date-parts 2011 , page 753-757, title Drought resistance is it really a complex trait, type article-journal, volume 38 , uris http//www.mendeley.com/documents/uuiddb34ce68-e6a1-4766-a98a-fb7f82791ba1 , mendeley formattedCitation (Blum, 2011), plainTextFormattedCitation (Blum, 2011), previouslyFormattedCitation (Blum, 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Blum, 2011). Sorghum is native to Sub Saharan Africa, a region characterised by poorly distributed, unpredictable and erratic rainfall. Selection and cultivation by rural African farmers has led to the development of wider genotypic variation for tolerance to water stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Martin, given Steffen, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue January, issued date-parts 2016 , title Breeding strategies for the adaptation of sorghum ( Sorghum bicolor L . Moench ) as a novel crop for temperate Europe Examining Committee , type article-journal , uris http//www.mendeley.com/documents/uuidf6d2a200-30f6-487d-a930-abce200732c9 , mendeley formattedCitation (Martin, 2016), plainTextFormattedCitation (Martin, 2016), previouslyFormattedCitation (Martin, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Martin, 2016). South Sudan falls within the centre of sorghum domestication and cultivation which explains why over 70 of the total grain produced in the country is obtained from sorghum ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family FAO, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue September 2016, issued date-parts 2017 , title FAO in South Sudan, type report , uris http//www.mendeley.com/documents/uuid2ccf21fb-b0d4-4fc1-ae4a-9e4169d2e00e , mendeley formattedCitation (FAO, 2017a), plainTextFormattedCitation (FAO, 2017a), previouslyFormattedCitation (FAO, 2017a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017a). This data indicated that sorghum is the major staple cereal food crop in the country. In all the agro-ecologies, sorghum is wholly utilized with little or no waste ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 2276-7770, ISSN 2276-7770, abstract Resistant crop cultivars provide the most economical, practical and sustainable method of Striga control. However, the development of resistant sorghum cultivars slowed by the complexity of the environment and the host/parasite interactions, which made field resistance erratic and unreliable. Recent adventure of molecular markers to tag gene(s) that confer important traits offers new hope for Striga control. Significant progress has been made to identify molecular markers linked to Striga resistance in sorghum variety, N13. Five genomic regions (QTLs) associated with Striga resistance were identified. Flanking simple sequence repeats (SSRs) markers to each QTL were also identified and made available. The aim of this study was to transfer Striga resistance from, N13 to an elite farmer preferred sorghum cultivar, Tabat. Generations of F1, BC1F1, BC1S1 and BC2F1 populations were developed. F1 and BC1F1 generations were first genotyped and progenies with two or more QTLs were backcrossed to generate BC1F1 and BC2F1, respectively. BC2F1 were further genotyped and progenies with two different QTLs were intercrossed for foreground selection. BC2F1 progenies were selfed to generate BC2S1, BC2S2 population. 19 progenies, BC1S1, with Striga resistance QTLs were tested in Striga artificial infested plots. Progenies with the two or more QTLs showed high levels of Striga field resistance, confirming the effectiveness of marker assisted selection (MAS). Significant differences were observed among the progeny tested in the level of Striga resistance and other agronomical traits., author dropping-particle , family Yasir Ahmed Gamar Abdalla Hassan Mohamed, given , non-dropping-particle , parse-names false, suffix , container-title Greener Journal of Agricultural Sciences, id ITEM-1, issue 7, issued date-parts 2013 , page 550-556, title Introgression of Striga resistance genes into a Sudanese sorghum cultivar, Tabat, using marker assisted selection (MAS), type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid8b9bb1de-d8c2-4ad2-a833-2384fe3aa04e , mendeley formattedCitation (Yasir Ahmed Gamar Abdalla Hassan Mohamed, 2013), manualFormatting (Gamar and Mohamed, 2013), plainTextFormattedCitation (Yasir Ahmed Gamar Abdalla Hassan Mohamed, 2013), previouslyFormattedCitation (Yasir Ahmed Gamar Abdalla Hassan Mohamed, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Gamar and Mohamed, 2013). Giran sorghum is processed in many traditional ways across the country but the methods vary from one locality to another depending on local custom, culture as well as food habit. Sorghum is consumed mostly as a solid porridge or pudding (Asida and Cuin), porridge (Madida), flat bread or pancake known as Kisra ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/BGRES.0000024155.43149.71, ISSN 0925-9864, abstract Sorghum Sorghum bicolor (L.) Moench is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums., author dropping-particle , family C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, given G.C. Peterson, non-dropping-particle , parse-names false, suffix , dropping-particle , family 3, given 12, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given 4 4 5 D.T. Rosenow and G. Ejeta, non-dropping-particle , parse-names false, suffix , dropping-particle , family 51, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given , non-dropping-particle , parse-names false, suffix , container-title Genetic Resources and Crop Evolution, id ITEM-1, issue 5, issued date-parts 2004 , page 489-500, title Sorghums of the Sudan analysis of regional diversity and distribution, type article-journal, volume 51 , uris http//www.mendeley.com/documents/uuid70f9176c-f44b-4c18-84aa-e1266947bd44 , mendeley formattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), manualFormatting (Grenier et al., 2004), plainTextFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), previouslyFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Grenier et al., 2004). In certain cases, the flour is mixed with cassava to produce a solid texture and a palatable taste. Large quantities of sorghum are made into local beer known as Mou or Marisa and an alcoholic spirit known as Warragi. Fresh stalk is chewed as sugarcane and is sometimes crushed with mortars and pestle, the product of which is soaked in water to extract juice for cooking porridge and a dish called Awal-walla (a popular Dinka food). Sorghum stalk is also used as livestock feed and may provide fuel for cooking in the dry season. The shelled panicles and glumes are used to smoke cattle room and keep mosquitoes away ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251091616, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue April, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuidab431dec-6eaa-44e8-b90f-a42804ec5639 , mendeley formattedCitation (FAO, 2016), plainTextFormattedCitation (FAO, 2016), previouslyFormattedCitation (FAO, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2016) Sorghum genotypes grown in South Sudan are landraces of long duration with low yields ranging from 0.4 to 0.6 t ha1. So far, there has been no agricultural research conducted on sorghum and other crops in South Sudan due to the long periods of war and insecurity. The first attempt to initiate sorghum research in South Sudan started with the ICRISAT-HOPE project in 2009 whose broad objective was to increase the productivity of dryland sorghum in Eastern and Central Equatoria states ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family CIAT, given FAO, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2010 , number-of-pages 12-13, title SEED SYSTEM SECURITY ASSESSMENT SOUTHERN SUDAN, type report , uris http//www.mendeley.com/documents/uuid04143597-0498-4520-85ed-d603fa1da44b , mendeley formattedCitation (CIAT, 2010), plainTextFormattedCitation (CIAT, 2010), previouslyFormattedCitation (CIAT, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (CIAT, 2010) and the project has so far released two varieties ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family CIAT, given FAO, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2010 , number-of-pages 12-13, title SEED SYSTEM SECURITY ASSESSMENT SOUTHERN SUDAN, type report , uris http//www.mendeley.com/documents/uuid04143597-0498-4520-85ed-d603fa1da44b , id ITEM-2, itemData ISBN 9789251091616, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue April, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuidab431dec-6eaa-44e8-b90f-a42804ec5639 , mendeley formattedCitation (CIAT, 2010 FAO, 2016), plainTextFormattedCitation (CIAT, 2010 FAO, 2016), previouslyFormattedCitation (CIAT, 2010 FAO, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (CIAT, 2010 FAO, 2016). Another research program by AGRA PASS program based at Halima/Wau, Western Bahr El Ghazal state focuses on facilitating farmers access to high quality seeds of improved varieties, creating farmers awareness, encouraging farmers to test new varieties and promoting local seeds and input industry ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family CIAT, given FAO, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2010 , number-of-pages 12-13, title SEED SYSTEM SECURITY ASSESSMENT SOUTHERN SUDAN, type report , uris http//www.mendeley.com/documents/uuid04143597-0498-4520-85ed-d603fa1da44b , mendeley formattedCitation (CIAT, 2010), plainTextFormattedCitation (CIAT, 2010), previouslyFormattedCitation (CIAT, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (CIAT, 2010). Problem statement Sorghum production in all the six agro-ecological zones of South Sudan is constrained by frequent drought and prolonged dry spell leading to crop failure for most of the seasons. Most of the local landraces grown are susceptible to drought stress. Drought stress at seedling stage mainly occurs during May and August seasons in most states ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251091616, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue April, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuidab431dec-6eaa-44e8-b90f-a42804ec5639 , id ITEM-2, itemData ISBN 9789251097137, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue May, issued date-parts 2017 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid0b0d9c40-c905-45f8-84a9-4f1b04b5de39 , mendeley formattedCitation (FAO, 2016, 2017b), manualFormatting (FAO, 2016), plainTextFormattedCitation (FAO, 2016, 2017b), previouslyFormattedCitation (FAO, 2016, 2017b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2016) leading to replanting and gap filling to ensure germination ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family FAO, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue September 2016, issued date-parts 2017 , title FAO in South Sudan, type report , uris http//www.mendeley.com/documents/uuid2ccf21fb-b0d4-4fc1-ae4a-9e4169d2e00e , mendeley formattedCitation (FAO, 2017a), manualFormatting (FAO, 2017), plainTextFormattedCitation (FAO, 2017a), previouslyFormattedCitation (FAO, 2017a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017). Due to severity and frequent occurrence of the drought spell, a shift in the planting occurs and may extend into May and June months of the year ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251097137, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May, issued date-parts 2017 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid0b0d9c40-c905-45f8-84a9-4f1b04b5de39 , mendeley formattedCitation (FAO, 2017b), manualFormatting (FAO, 2017), plainTextFormattedCitation (FAO, 2017b), previouslyFormattedCitation (FAO, 2017b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017). Food and Agriculture Organization ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251091616, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue April, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuidab431dec-6eaa-44e8-b90f-a42804ec5639 , mendeley formattedCitation (FAO, 2016), plainTextFormattedCitation (FAO, 2016), previouslyFormattedCitation (FAO, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2016) indicated that farm yields do not exceed 0.6 t ha-1 across the country but there is a potential for 4.5-7.0 t ha-1 yield. The problem of low yields due to low moisture availability is compounded by the long maturation of the local landraces of Shalla, Kec, Bher ,Ngethin, Nyandok,nuerbai,Rapjung ,Rabdit, Akuorachot , Aluel and Ayella which may take up from 120-220 days. .According to ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p276-287, ISSN 23224541, author dropping-particle , family Kahiu Ngugi1, Rachael Maswili1, 2, given Cecilia Muchira1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1Department, given , non-dropping-particle , parse-names false, suffix , container-title About IJSRPUB. com, id ITEM-1, issue May, issued date-parts 2013 , page 276-287, title Assessing relationships in kenyan sorghum landraces by use of simple sequence repeat molecular ers, type article-journal, volume 1(8) , uris http//www.mendeley.com/documents/uuid8d7302ae-2d0d-417b-bc22-886ec3c60e78 , mendeley formattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013), manualFormatting Ngugi et al., (2013), plainTextFormattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Ngugi et al., (2013) sorghum genotypes grown in semi-arid areas either escape drought and therefore mature early or have inherent drought tolerance mechanisms that allow them to produce some yield despite the stress. In South Sudan, despite the fact that most of the landraces are early-maturing, grain yield losses due to drought stress are estimated to be at 53 mainly because of lack of drought tolerance mechanisms ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251097137, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May, issued date-parts 2017 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid0b0d9c40-c905-45f8-84a9-4f1b04b5de39 , mendeley formattedCitation (FAO, 2017b), manualFormatting (FAO, 2017), plainTextFormattedCitation (FAO, 2017b), previouslyFormattedCitation (FAO, 2017b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017). There is a need to collect, screen ,identify and breed germplasm with inherent drought tolerance alleles that together with drought escaping genes exhibited in earliness could be improved and harnessed for adaptation to drought stress in water stress prone agro-ecologies of the East African region ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12966/jra.08.02.2013, ISSN 2328-4951, abstract Drought stress is the major abiotic factor that limits cassava productivity in many agro-ecological regions of sub-saharan Africa. In this study, stay-green trait in two transgenic cassava genotypes (transformed with isopentenyl transferase (ipt) gene for improved drought tolerance) and six non-transgenic cassava genotypes were evaluated under green-house condi- tions. Leaf abscission (for leaf retention), elongation of the last internodes, photosynthetic rates, and stomatal conductance were determined in these cassava genotypes subjected to three levels of water stress treatments (0, 30, and 60 ) and a positive control or fully irrigated plants. Two non transgenic genotypes (98-0002 and 98-2226) and one transgenic line (529-48) that expressed relatively high level of stay green or leaf retention, also exhibited significantly higher photosynthetic rates, internode elongation and relatively low stomatal conductance compared to other genotypes. Non transgenic genotypes 91-02322 and TME-3 and transgenic line 529-28, expressed moderate levels of stay green and non transgenic genotype 95-0306 and wild type TMS 60444 (for the transgenic lines) were highly susceptible to the water stress treatments. The results reported here showed there was a positive correlation between leaf retention, photosynthetic rates, internode elongation and stomatal conductance., author dropping-particle , family Kahiu Ngugi 1,, Charles Orek 1,2, given Agnes Mwangu2019ombe, non-dropping-particle , parse-names false, suffix , container-title Journal of Renewable Agriculture, id ITEM-1, issue 5, issued date-parts 2013 , page 77-83, title Morphological and Physiological Measurement of the Stay-Green Trait in Transgenic and Non-Transgenic Cassava under Green-House Water Stress Conditions, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid02bbe90c-3e3e-4c4e-bfad-0e673532ef51 , mendeley formattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013), manualFormatting (Ngugi and Orek, 2013), plainTextFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013), previouslyFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi and Orek, 2013). Justification of the study Sorghum has its centre of origin in Africa and specifically in the Ethiopia-Sudan region. In the past decades, South Sudanese subsistence farming communities have identified, selected and sustained diverse landraces of sorghum with better adaptation to their agro-ecological zones of evolution particularly in Uppernile, Bar-E Ghazel and Equatoria regions. The 2009 sorghum germplasm search in the two states of Central and Eastern Equatoria led to the collection of forty seven accessions, each with a different landrace name portraying the level of diversity that exists in South Sudan. These collections have not been characterized hence their genetic potential is not known. Evaluation of these collections together with hitherto undescribed germplasm introduced from other regions is necessary in order to identify drought tolerant cultivars that combine earliness and high yield traits useful in mitigating the effects of drought. The development of drought tolerant genotypes with early maturing and high yielding traits will help reduce frequent crop failures and increase the number of sowing seasons for sorghum production from one season to three seasons per year. This will ensure food and nutrition security for the people of South Sudan. Objective The main objective of this research was to increase sorghum productivity in the rural and marginal areas of South Sudan for food security and poverty alleviation through identification of drought tolerant sorghum genotypes which are high yielding. Specific objectives of the study To identify drought tolerant , early maturing and high yielding sorghum genotypes for drought prone agro-ecological zones To introgress drought tolerance from identified donor sources into high yielding and drought stress susceptible late maturing farmer preferred sorghum lines Hypothesis There is genetic variation for drought tolerance, earliness and high grain yield among the South Sudanese landraces and exotic lines. South Sudan sorghum landraces have high combining ability for drought tolerance when crossed with stay-green donor sources CHAPTER TWO LITERATURE REVIEW 2.1 Sorghum (Sorghum Bicolor (L) Moench) Sorghum (Sorghum bicolor (L) Moench) has a chromosome number of 2n2x-20 and is a key C4 crop cultivated for human and livestock consumption, building materials and brewing. Sorghum is the second vital crop after maize (Zea mays) in the tropics able to give high yield under harsh environmental conditions where other cereal crops failed to grow and produce. Sorghum is more tolerant to several stresses including heat, drought stress, flooding, dry spell, low soil fertility and salinity relative to other cereal crops ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/BGRES.0000024155.43149.71, ISSN 0925-9864, abstract Sorghum Sorghum bicolor (L.) Moench is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums., author dropping-particle , family C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, given G.C. Peterson, non-dropping-particle , parse-names false, suffix , dropping-particle , family 3, given 12, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given 4 4 5 D.T. Rosenow and G. Ejeta, non-dropping-particle , parse-names false, suffix , dropping-particle , family 51, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given , non-dropping-particle , parse-names false, suffix , container-title Genetic Resources and Crop Evolution, id ITEM-1, issue 5, issued date-parts 2004 , page 489-500, title Sorghums of the Sudan analysis of regional diversity and distribution, type article-journal, volume 51 , uris http//www.mendeley.com/documents/uuid70f9176c-f44b-4c18-84aa-e1266947bd44 , mendeley formattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), manualFormatting (Grenier et al., 2004), plainTextFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), previouslyFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Grenier et al., 2004). The crop survives in warm and dry regions as well as cool weather and waterlogged habitats ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Morka., given Eyerusalem Arusi, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue June, issued date-parts 2015 , number-of-pages 5-70, title Physiological Indices for Drought Tolerance in Stay-green Sorghum (, type report , uris http//www.mendeley.com/documents/uuid2a1b438d-a114-431b-856b-6aac24e8ed2b , mendeley formattedCitation (Morka., 2015), manualFormatting (Zhang et al., 2015), plainTextFormattedCitation (Morka., 2015), previouslyFormattedCitation (Morka., 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Zhang et al., 2015). Therefore, sorghum has a wider adaptation, making it an important crop to billons of human population living in the arid and semi arid drylands of the world ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/acsj.v18i4.68644, ISSN 2072-6589, abstract Characterisation of the available Kenyan sorghum genetic diversity is important for understanding the dynamics of the genetic resources and for improving and sustaining sorghum productivity. The aim of this study was to assess the extent and structure of diversity in sorghum landraces from Kenya. Phenotypic data were used to assess diversity in 148 sorghum accessions collected from Western, Turkana, Coast and Eastern regions of Kenya. The accessions were phenotyped using qualitative and quantitative morphological characters. Most of the accessions were high yielding as revealed by the means of panicle branches (43), panicle length (21cm), and grain weight (1.5 g). Majority of the sorghums were late maturing and tall as shown by the mean number of days to 50 flowering (88 days), number of leaves and nodes. Turkana and coast sorghums had similarities in maturity, height and panicle length. The number of panicle branches had the highest Broad-sense heritability (0.957). Majority of the sorghums had dull green midrib (49.55), no basal tillers (83), had waxy bloom (39.64) and produced prop roots (87). Loose and semi-loose erect panicles dominated (69) while 83 of the accessions had slightly exerted peduncles. The two Eigen values in PCA explained 67 of the total variance. Phenotypic cluster analysis gave two major groups subdivided into four sub clusters., author dropping-particle , family Ngugi, given K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Maswili, given R, non-dropping-particle , parse-names false, suffix , container-title African Crop Science Journal, id ITEM-1, issue 4, issued date-parts 2010 , page 165-173, title Phenotypic diversity in sorghum landraces from kenya, type article-journal, volume 18 , uris http//www.mendeley.com/documents/uuid459fc10e-11b9-49ab-9563-c8c21f4cfdfd , id ITEM-2, itemData DOI 10.12966/jra.08.02.2013, ISSN 2328-4951, abstract Drought stress is the major abiotic factor that limits cassava productivity in many agro-ecological regions of sub-saharan Africa. In this study, stay-green trait in two transgenic cassava genotypes (transformed with isopentenyl transferase (ipt) gene for improved drought tolerance) and six non-transgenic cassava genotypes were evaluated under green-house condi- tions. Leaf abscission (for leaf retention), elongation of the last internodes, photosynthetic rates, and stomatal conductance were determined in these cassava genotypes subjected to three levels of water stress treatments (0, 30, and 60 ) and a positive control or fully irrigated plants. Two non transgenic genotypes (98-0002 and 98-2226) and one transgenic line (529-48) that expressed relatively high level of stay green or leaf retention, also exhibited significantly higher photosynthetic rates, internode elongation and relatively low stomatal conductance compared to other genotypes. Non transgenic genotypes 91-02322 and TME-3 and transgenic line 529-28, expressed moderate levels of stay green and non transgenic genotype 95-0306 and wild type TMS 60444 (for the transgenic lines) were highly susceptible to the water stress treatments. The results reported here showed there was a positive correlation between leaf retention, photosynthetic rates, internode elongation and stomatal conductance., author dropping-particle , family Kahiu Ngugi 1,, Charles Orek 1,2, given Agnes Mwangu2019ombe, non-dropping-particle , parse-names false, suffix , container-title Journal of Renewable Agriculture, id ITEM-2, issue 5, issued date-parts 2013 , page 77-83, title Morphological and Physiological Measurement of the Stay-Green Trait in Transgenic and Non-Transgenic Cassava under Green-House Water Stress Conditions, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid02bbe90c-3e3e-4c4e-bfad-0e673532ef51 , mendeley formattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013 Ngugi Maswili, 2010), manualFormatting (Ngugi and Maswili, 2010 Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013 Ngugi Maswili, 2010), previouslyFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013 Ngugi Maswili, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi and Maswili, 2010 Ngugi et al., 2013). 2.2 Origin and distribution of sorghum Sorghum originated in Eastern Africa where its first place of domestication was in the Ethiopia- Sudan region ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/BGRES.0000024155.43149.71, ISSN 0925-9864, abstract Sorghum Sorghum bicolor (L.) Moench is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums., author dropping-particle , family C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud, given G.C. Peterson, non-dropping-particle , parse-names false, suffix , dropping-particle , family 3, given 12, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given 4 4 5 D.T. Rosenow and G. Ejeta, non-dropping-particle , parse-names false, suffix , dropping-particle , family 51, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given , non-dropping-particle , parse-names false, suffix , container-title Genetic Resources and Crop Evolution, id ITEM-1, issue 5, issued date-parts 2004 , page 489-500, title Sorghums of the Sudan analysis of regional diversity and distribution, type article-journal, volume 51 , uris http//www.mendeley.com/documents/uuid70f9176c-f44b-4c18-84aa-e1266947bd44 , mendeley formattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), manualFormatting (Grenier et al., 2004), plainTextFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004), previouslyFormattedCitation (C. Grenier , P.J. Bramel , J.A. Dahlberg , A. El-Ahmadi , M. Mahmoud et al., 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Grenier et al., 2004). Genotypic diversity of domesticated and undomesticated species are common in the Ethiopia- Sudan region some of which have better adaptation to several agro-ecological zones in Africa, Asia, Australia and America ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract Drought is the major environmental factor constraining crop production globally. Identifying and understanding the function of genes and gene networks that contribute to improved plant drought resistance under water-limited conditions is a fundamental component of sorghum breeding programs in Australia and the United States. In particular, genes located in four genomic regions (Stg1, Stg2, Stg3 and Stg4) controlling the functional basis of the B35 source of stay-green are being sought. Plants with the stay-green drought-resistance trait maintain green stems and upper leaves when water is limiting during grain filling. This paper discusses the multi-disciplinary approach to gene discovery implemented by Australian and U.S. scientists in pursuit of the key stay-green genes. In this project, map-based gene cloning is the primary approach to gene discovery. Multiple cycles of phenotyping and genotyping have enabled scientists to close-in on the genes of interest via fine-mapping, and will ultimately lead to the discovery of gene function. Candidate genes will be identified within each of the four genomic regions using an integrated genetic and physical map of sorghum, together with detailed physiological dissection of genotypes with different stay-green alleles. Proof of gene function will follow. Gene function in a range of environments will be assessed in silico using crop simulation modelling. Overall, this integrated approach to gene discovery will enable plant breeders to more efficiently custom-make sorghum varieties for specific water-limited environments. The discovery of stay-green genes in sorghum by Australian and U.S. scientists will lead to improved drought-resistance in sorghum, and potentially other major cereals., author dropping-particle , family Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, given Richard, non-dropping-particle , parse-names false, suffix , container-title 4th International Crop Science Congress, id ITEM-1, issue November 2015, issued date-parts 2004 , page 1-6, title Discovering Stay-Green Drought Tolerance Genes in Sorghum A Multidisciplinary Approach, type article-journal , uris http//www.mendeley.com/documents/uuidde2b9391-3c8a-4384-9f12-cb9a11c5fb75 , mendeley formattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004), manualFormatting (Borrell et al., 2004 Gamar and Mohamed, 2013 Ngugi and Orek 2013 Grenier et al., 2004 ), plainTextFormattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004), previouslyFormattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2004 Gamar and Mohamed, 2013 Ngugi and Orek 2013 Grenier et al., 2004 ). In East Africa, over 70 of cultivation is carried out mainly in dry and warm lowlands with low soil fertility that constrain production of other crops ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1080/02571862.2016.1143043, ISBN 0257-1862, ISSN 02571862, abstract 2016 Southern African Plant Soil Sciences Committee.Sorghum is one of the most important cereal crops worldwide after wheat, rice, maize and barley. Examining the present socio-economic conditions of sorghum-producing farmers in different agro-ecologies in Ethiopia is of importance for the design of improvement strategies. The objectives of this study were to evaluate the sorghum production system and patterns, major production constraints and related coping strategies in north-eastern Ethiopia. Twelve sorghum-growing villages in the North Welo, South Welo and Waghemra districts were surveyed. Descriptive statistics and a generalised additive model were used for data analysis. Constraints affecting the productivity of sorghum include moisture stress, insect pests, striga, farmland shortage, poor soil fertility, diseases, and low-yielding local cultivars. Among the constraints, drought at the grain-filling stage was identified as the most important production problem in the target region. The productivity of sorghum was also hindered by the use of local drought-tolerant but low-yielding landraces, because farmers had been forced to abandon high-yielding and late-maturing landrace cultivars because of the frequent occurrence of drought. To enhance sorghum productivity, farmers knowledge and practices, and production constraints need to be integrated from the initial stages of breeding and technology development., author dropping-particle , family Amelework, given Beyene A., non-dropping-particle , parse-names false, suffix , dropping-particle , family Shimelis, given Hussein A., non-dropping-particle , parse-names false, suffix , dropping-particle , family Tongoona, given Pangirayi, non-dropping-particle , parse-names false, suffix , dropping-particle , family Mengistu, given Fentahun, non-dropping-particle , parse-names false, suffix , dropping-particle , family Laing, given Mark D., non-dropping-particle , parse-names false, suffix , dropping-particle , family Ayele, given Dawit Getnet, non-dropping-particle , parse-names false, suffix , container-title South African Journal of Plant and Soil, id ITEM-1, issue 3, issued date-parts 2016 , page 207-217, title Sorghum production systems and constraints, and coping strategies under drought-prone agro-ecologies of Ethiopia, type article-journal, volume 33 , uris http//www.mendeley.com/documents/uuide3ec895c-25a9-4c9d-9d01-a7b9b74702a6 , mendeley formattedCitation (Amelework et al., 2016), manualFormatting (Amelework et al., 2016), plainTextFormattedCitation (Amelework et al., 2016), previouslyFormattedCitation (Amelework et al., 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2016). In South Sudan for example, while the crop is cultivated in all the states, it is more common in the marginal areas with low rainfall and poor soil fertility where it occupies 859,662 hectares and produces 634,700 metric tonnes annually ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251097137, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May, issued date-parts 2017 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid0b0d9c40-c905-45f8-84a9-4f1b04b5de39 , mendeley formattedCitation (FAO, 2017b), manualFormatting (FAO, 2017, plainTextFormattedCitation (FAO, 2017b), previouslyFormattedCitation (FAO, 2017b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017). Sorghum production is in the hands of small scale poor farmers who grow low yielding landraces using farmer saved seed and or from and farmer-to-farmer exchanges ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251091616, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue April, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuidab431dec-6eaa-44e8-b90f-a42804ec5639 , mendeley formattedCitation (FAO, 2016), plainTextFormattedCitation (FAO, 2016), previouslyFormattedCitation (FAO, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2016). In Kenya, where semi arid area covers75 of land mass ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p276-287, ISSN 23224541, author dropping-particle , family Kahiu Ngugi1, Rachael Maswili1, 2, given Cecilia Muchira1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1Department, given , non-dropping-particle , parse-names false, suffix , container-title About IJSRPUB. com, id ITEM-1, issue May, issued date-parts 2013 , page 276-287, title Assessing relationships in kenyan sorghum landraces by use of simple sequence repeat molecular ers, type article-journal, volume 1(8) , uris http//www.mendeley.com/documents/uuid8d7302ae-2d0d-417b-bc22-886ec3c60e78 , mendeley formattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013), manualFormatting (Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Rachael Maswili1, 2 1Department, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi et al., 2013), sorghum provides food and nutritional security and serves as a suitable alternative for maize. The crop is predominantly grown in Eastern, Western and Nyanza former provinces which produce 99 of total grain sorghum in Kenya ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p154-162, ISBN 3070900100, ISSN 2322-4541, abstract Drought stress is a major constraint to sorghum production in Kenya, especially during flowering stage. This study aimed at developing drought tolerant sorghum varieties by transferring the stay green trait that confers drought tolerance in sorghum from a mapped and characterized donor source into an adapted farmer preferred variety. The drought tolerance donor source, E36-1 originally from Ethiopia was backcrossed into a Kenyan farmer-preferred variety, Ochuti until BC2F1 generation and the stay-green Quantitative Trait Loci (QTL) were transferred through Marker Assisted Breeding (MAB) strategy. Five polymorphic Simple Sequence Repeat (SSR) markers were used to select the 3 stay green QTL of E36-1 found in SBI-01, SBI-07 and SBI-10 linkage groups. In the F1 generation, two of these QTL, were transferred into three genotypes. In the BC1F1 generation, 32 genotypes had at least one QTL incorporated. From a population of 157 BC2F1 progenies, 45 genotypes had incorporated either one or two of the stay-green QTL. Despite a few number of genotypes obtained through the backcrosses, the results showed that stay-green QTL and consequently drought tolerance can be transferred successfully into farmer preferred sorghum varieties through MAB., author dropping-particle , family Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3, given Eunice W. Mutitu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1University, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Scientific Research in Knowledge, id ITEM-1, issue 6, issued date-parts 2013 , page 154-162, title Improving drought tolerance in Sorghum bicolor L. Moench Marker-assisted transfer of the stay-green quantitative trait loci (QTL) from a characterized donor source into a local farmer variety, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid9512ed63-81f0-41cf-8b72-01d141f0d051 , mendeley formattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), manualFormatting (Ngugi and Maswili, 2010) Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/acsj.v18i4.68644, ISSN 2072-6589, abstract Characterisation of the available Kenyan sorghum genetic diversity is important for understanding the dynamics of the genetic resources and for improving and sustaining sorghum productivity. The aim of this study was to assess the extent and structure of diversity in sorghum landraces from Kenya. Phenotypic data were used to assess diversity in 148 sorghum accessions collected from Western, Turkana, Coast and Eastern regions of Kenya. The accessions were phenotyped using qualitative and quantitative morphological characters. Most of the accessions were high yielding as revealed by the means of panicle branches (43), panicle length (21cm), and grain weight (1.5 g). Majority of the sorghums were late maturing and tall as shown by the mean number of days to 50 flowering (88 days), number of leaves and nodes. Turkana and coast sorghums had similarities in maturity, height and panicle length. The number of panicle branches had the highest Broad-sense heritability (0.957). Majority of the sorghums had dull green midrib (49.55), no basal tillers (83), had waxy bloom (39.64) and produced prop roots (87). Loose and semi-loose erect panicles dominated (69) while 83 of the accessions had slightly exerted peduncles. The two Eigen values in PCA explained 67 of the total variance. Phenotypic cluster analysis gave two major groups subdivided into four sub clusters., author dropping-particle , family Ngugi, given K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Maswili, given R, non-dropping-particle , parse-names false, suffix , container-title African Crop Science Journal, id ITEM-1, issue 4, issued date-parts 2010 , page 165-173, title Phenotypic diversity in sorghum landraces from kenya, type article-journal, volume 18 , uris http//www.mendeley.com/documents/uuid459fc10e-11b9-49ab-9563-c8c21f4cfdfd , mendeley formattedCitation (Ngugi Maswili, 2010), manualFormatting (Ngugi and Maswili, 2010), plainTextFormattedCitation (Ngugi Maswili, 2010), previouslyFormattedCitation (Ngugi Maswili, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi and Maswili, 2010) Ngugi et al., 2013). On-farm yield ranges from 0.6-to 1.5 t ha1 for openly pollinated varieties and 4.5 to 7.0 t ha1 for hybrids ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/acsj.v18i4.68644, ISSN 2072-6589, abstract Characterisation of the available Kenyan sorghum genetic diversity is important for understanding the dynamics of the genetic resources and for improving and sustaining sorghum productivity. The aim of this study was to assess the extent and structure of diversity in sorghum landraces from Kenya. Phenotypic data were used to assess diversity in 148 sorghum accessions collected from Western, Turkana, Coast and Eastern regions of Kenya. The accessions were phenotyped using qualitative and quantitative morphological characters. Most of the accessions were high yielding as revealed by the means of panicle branches (43), panicle length (21cm), and grain weight (1.5 g). Majority of the sorghums were late maturing and tall as shown by the mean number of days to 50 flowering (88 days), number of leaves and nodes. Turkana and coast sorghums had similarities in maturity, height and panicle length. The number of panicle branches had the highest Broad-sense heritability (0.957). Majority of the sorghums had dull green midrib (49.55), no basal tillers (83), had waxy bloom (39.64) and produced prop roots (87). Loose and semi-loose erect panicles dominated (69) while 83 of the accessions had slightly exerted peduncles. The two Eigen values in PCA explained 67 of the total variance. Phenotypic cluster analysis gave two major groups subdivided into four sub clusters., author dropping-particle , family Ngugi, given K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Maswili, given R, non-dropping-particle , parse-names false, suffix , container-title African Crop Science Journal, id ITEM-1, issue 4, issued date-parts 2010 , page 165-173, title Phenotypic diversity in sorghum landraces from kenya, type article-journal, volume 18 , uris http//www.mendeley.com/documents/uuid459fc10e-11b9-49ab-9563-c8c21f4cfdfd , mendeley formattedCitation (Ngugi Maswili, 2010), manualFormatting (Ngugi and Maswili, 2010), plainTextFormattedCitation (Ngugi Maswili, 2010), previouslyFormattedCitation (Ngugi Maswili, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi and Maswili, 2010). The high yield in Kenya is attributed to a well established extension system, modern farming practices, improved technologies and breakthrough in yield barriers through cytoplasmic male sterility ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p154-162, ISBN 3070900100, ISSN 2322-4541, abstract Drought stress is a major constraint to sorghum production in Kenya, especially during flowering stage. This study aimed at developing drought tolerant sorghum varieties by transferring the stay green trait that confers drought tolerance in sorghum from a mapped and characterized donor source into an adapted farmer preferred variety. The drought tolerance donor source, E36-1 originally from Ethiopia was backcrossed into a Kenyan farmer-preferred variety, Ochuti until BC2F1 generation and the stay-green Quantitative Trait Loci (QTL) were transferred through Marker Assisted Breeding (MAB) strategy. Five polymorphic Simple Sequence Repeat (SSR) markers were used to select the 3 stay green QTL of E36-1 found in SBI-01, SBI-07 and SBI-10 linkage groups. In the F1 generation, two of these QTL, were transferred into three genotypes. In the BC1F1 generation, 32 genotypes had at least one QTL incorporated. From a population of 157 BC2F1 progenies, 45 genotypes had incorporated either one or two of the stay-green QTL. Despite a few number of genotypes obtained through the backcrosses, the results showed that stay-green QTL and consequently drought tolerance can be transferred successfully into farmer preferred sorghum varieties through MAB., author dropping-particle , family Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3, given Eunice W. Mutitu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1University, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Scientific Research in Knowledge, id ITEM-1, issue 6, issued date-parts 2013 , page 154-162, title Improving drought tolerance in Sorghum bicolor L. Moench Marker-assisted transfer of the stay-green quantitative trait loci (QTL) from a characterized donor source into a local farmer variety, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid9512ed63-81f0-41cf-8b72-01d141f0d051 , mendeley formattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), manualFormatting (Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi et al., 2013). In Uganda, sorghum is a leading staple cereal particularly in the West, Northern and Eastern parts where it is consumed in the form of bread, ugali and local alcoholic beverages ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family E. Awori, M. Kiryowa, A. Basirika, F. Dradiku, R. Kahunza, A. Oriba, C. Edonia, given R. Olupot1 and J. Mukalazi, non-dropping-particle , parse-names false, suffix , dropping-particle , family Abi, given , non-dropping-particle , parse-names false, suffix , container-title Uganda Journal of Agricultural Sciences, id ITEM-1, issue 1, issued date-parts 2015 , page 139-148, title Performance of elite grain sorghum varieties in the West Nile Agro-ecological Zones, type article-journal, volume 16 , uris http//www.mendeley.com/documents/uuid0254076e-bf49-4884-9080-26253746c1d3 , mendeley formattedCitation (E. Awori, M. Kiryowa, A. Basirika, F. Dradiku, R. Kahunza, A. Oriba, C. Edonia Abi, 2015), manualFormatting (Awori et al., 2015), plainTextFormattedCitation (E. Awori, M. Kiryowa, A. Basirika, F. Dradiku, R. Kahunza, A. Oriba, C. Edonia Abi, 2015), previouslyFormattedCitation (E. Awori, M. Kiryowa, A. Basirika, F. Dradiku, R. Kahunza, A. Oriba, C. Edonia Abi, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Awori et al., 2015). The crop yields up to 1.52 t ha1 for well managed local varieties and 5 t ha1 for improved open pollinated varieties ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Robert, given Olupot John, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue December, issued date-parts 2011 , title No Title Genetic Analysis of Striga hermonthica Resistance Sorghum (Sorghum Bicolor) Genotypes in Eastern Uganda., type article-journal , uris http//www.mendeley.com/documents/uuidcd59cba3-f827-46b5-b352-0a651a6584c1 , mendeley formattedCitation (Robert, 2011), plainTextFormattedCitation (Robert, 2011), previouslyFormattedCitation (Robert, 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Robert, 2011). In Ethiopia, sorghum is utilized in various forms including local bread, floor, cake, local alcohol beverages and roasted or boiled grain ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework et al, 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al, 2012). In Ethiopia, sorghum is utilized in various forms including making local bread, floor, cake and for preparing local alcoholic beverages and is consumed as roasted or boiled grain ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework and Beyene, 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework and Beyene, 2012). In Eritrea, sorghum accounts for more than 50 of the total food crop produce annually and is grown more in the warm lowland of Eritrea where rainfall is erratic and unpredictable ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4236/ajps.2015.69141, ISSN 2158-2742, abstract Sorghum (Sorghum bicolour (L.) Moench) grown under rain-fed conditions is usually affected by drought stress at different stages, resulting in reduced yield. The assessment of variation in mor-pho-physiological traits contributing towards drought tolerance at these stages is of vital impor-tance. This study was conducted using a split plot design with three replications to evaluate 25 sorghum accessions at post flowering stage under well watered and drought stress conditions at Hamelmalo Agricultural College. The data of 14 different morpho-physiological traits were sub-jected to analysis of variance, estimation of genetic variability and heritability and principal com-ponent analysis. We analyzed variance for seedling vigor, number of leaves, leaf area, stay-green, peduncle exsertion, panicle length and width, plant height, days to flowering and maturity, grain yield, biomass and harvest index under drought stress and irrigated conditions. The results showed that genotypic differences were significant at P 0.05 – 0.001. High magnitude of phe-notypic and genotypic coefficient of variations for plant height, harvest index and biomass as well as high heritability for days to flowering, panicle length, days to maturity and over all agronomic score were recorded. Principal component (PC) analysis showed that the first 4 PCs had Eigen value 1 explaining 74.6 of the total variation with grain yield, biomass, stay-green, leaf area, peduncle exsertion and days to flowering and maturity being the most important characters in PC1 and PC2. This research demonstrated high diversity for the characters studied. Moreover, the result showed that drought stress reduced the yield of some genotypes, though others were tole-rant to drought. Accessions EG 885, EG 469, EG 481, EG 849, Hamelmalo, EG 836 and EG 711 were Corresponding author. Tesfamichael et al. 1411 identified as superior for post-flowering drought tolerance and could be used by breeders in im-provement programs., author dropping-particle , family Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, given Aggrey Bernard Nyende2, non-dropping-particle , parse-names false, suffix , container-title American Journal of Plant Sciences, id ITEM-1, issue 6, issued date-parts 2015 , page 1410-1424, title Genetic Variation among Sorghum (Sorghum bicolor L. Moench) Landraces from Eritrea under Post-Flowering Drought Stress Conditions, type article-journal, volume 6 , uris http//www.mendeley.com/documents/uuid89f1c00f-d432-45c5-a43a-6755b0404895 , mendeley formattedCitation (Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015), manualFormatting (Tesfamichael et al., 2015), plainTextFormattedCitation (Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015), previouslyFormattedCitation (Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tesfamichael et al., 2015). 2.3 Constraints to sorghum production in East Africa The average on-farm sorghum yield in Eastern Africa is 0.6-1.5 t ha1 vis-a-vis worldwide average yield of more than 4.5 t ha1 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/acsj.v18i4.68644, ISSN 2072-6589, abstract Characterisation of the available Kenyan sorghum genetic diversity is important for understanding the dynamics of the genetic resources and for improving and sustaining sorghum productivity. The aim of this study was to assess the extent and structure of diversity in sorghum landraces from Kenya. Phenotypic data were used to assess diversity in 148 sorghum accessions collected from Western, Turkana, Coast and Eastern regions of Kenya. The accessions were phenotyped using qualitative and quantitative morphological characters. Most of the accessions were high yielding as revealed by the means of panicle branches (43), panicle length (21cm), and grain weight (1.5 g). Majority of the sorghums were late maturing and tall as shown by the mean number of days to 50 flowering (88 days), number of leaves and nodes. Turkana and coast sorghums had similarities in maturity, height and panicle length. The number of panicle branches had the highest Broad-sense heritability (0.957). Majority of the sorghums had dull green midrib (49.55), no basal tillers (83), had waxy bloom (39.64) and produced prop roots (87). Loose and semi-loose erect panicles dominated (69) while 83 of the accessions had slightly exerted peduncles. The two Eigen values in PCA explained 67 of the total variance. Phenotypic cluster analysis gave two major groups subdivided into four sub clusters., author dropping-particle , family Ngugi, given K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Maswili, given R, non-dropping-particle , parse-names false, suffix , container-title African Crop Science Journal, id ITEM-1, issue 4, issued date-parts 2010 , page 165-173, title Phenotypic diversity in sorghum landraces from kenya, type article-journal, volume 18 , uris http//www.mendeley.com/documents/uuid459fc10e-11b9-49ab-9563-c8c21f4cfdfd , mendeley formattedCitation (Ngugi Maswili, 2010), manualFormatting (Ngugi and Maswili, 2010), plainTextFormattedCitation (Ngugi Maswili, 2010), previouslyFormattedCitation (Ngugi Maswili, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi and Maswili, 2010). While yield losses are attributed to many abiotic and biotic stresses, water stress is ranked as the major yield constraint globally ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , id ITEM-2, itemData author dropping-particle , family Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., given Subhash Bharani and Vinayak Turaidar, non-dropping-particle , parse-names false, suffix , container-title Int. J. Pure App. Biosci., id ITEM-2, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid69473559-95d1-411c-87d6-aa2627b99dc0 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), manualFormatting (Beyene et al., 2015 Dalawai, 2017), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Dalawai, 2017) because it is hard to predict at various phases of crop growth of cropping season in semi-arid areas that rely on rainfall. Sorghum grain yield losses attributed to water stress in South Sudan is estimated to be from 53 70 in the semi arid regionADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Programme, given World Food, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue March, issued date-parts 2016 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid89f5d073-af2c-4d68-af8b-c6ef904edf02 , mendeley formattedCitation (Programme, 2016), manualFormatting (FAO, 2016), plainTextFormattedCitation (Programme, 2016), previouslyFormattedCitation (Programme, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2016). 2.4 Effects of drought stress on plant development and productivity Water stress poses critical threat to world wide food and nutritional security ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p154-162, ISBN 3070900100, ISSN 2322-4541, abstract Drought stress is a major constraint to sorghum production in Kenya, especially during flowering stage. This study aimed at developing drought tolerant sorghum varieties by transferring the stay green trait that confers drought tolerance in sorghum from a mapped and characterized donor source into an adapted farmer preferred variety. The drought tolerance donor source, E36-1 originally from Ethiopia was backcrossed into a Kenyan farmer-preferred variety, Ochuti until BC2F1 generation and the stay-green Quantitative Trait Loci (QTL) were transferred through Marker Assisted Breeding (MAB) strategy. Five polymorphic Simple Sequence Repeat (SSR) markers were used to select the 3 stay green QTL of E36-1 found in SBI-01, SBI-07 and SBI-10 linkage groups. In the F1 generation, two of these QTL, were transferred into three genotypes. In the BC1F1 generation, 32 genotypes had at least one QTL incorporated. From a population of 157 BC2F1 progenies, 45 genotypes had incorporated either one or two of the stay-green QTL. Despite a few number of genotypes obtained through the backcrosses, the results showed that stay-green QTL and consequently drought tolerance can be transferred successfully into farmer preferred sorghum varieties through MAB., author dropping-particle , family Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3, given Eunice W. Mutitu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1University, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Scientific Research in Knowledge, id ITEM-1, issue 6, issued date-parts 2013 , page 154-162, title Improving drought tolerance in Sorghum bicolor L. Moench Marker-assisted transfer of the stay-green quantitative trait loci (QTL) from a characterized donor source into a local farmer variety, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid9512ed63-81f0-41cf-8b72-01d141f0d051 , mendeley formattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), manualFormatting (Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi et al., 2013). The severity of drought is unpredictable because of its dependence on many factors such as occurrence, duration and soil moisture retention capacity which are hard to quantify simultaneously ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/A1009673126345, ISBN 1380-3743, ISSN 13803743, abstract Drought is a serious agronomic problem and the single greatest factor contributing to crop yield loss in the world today. This problem may be alleviated by developing crops that are well adapted to dry-land environments. Sorghum (Sorghum bicolor (L.) Moench) is one of the most drought-tolerant grain crops and is an excellent crop model for evaluating mechanisms of drought tolerance. In this study, a set of 98 recombinant inbred (RI) sorghum lines was developed from a cross between two genotypes with contrasting drought reactions, TX7078 (pre-flowering-tolerant, post-flowering susceptible) and B35 (pre-flowering susceptible, post-flowering-tolerant). The RI population was characterized under drought and non-drought conditions for the inheritance of traits associated with post-flowering drought tolerance and for potentially related components of grain development. Quantitative trait loci (QTL) analysis identified 13 regions of the genome associated with one or more measures of post-flowering drought tolerance. Two QTL were identified with major effects on yield and staygreen under post-flowering drought. These loci were also associated with yield under fully irrigated conditions suggesting that these tolerance loci have pleiotropic effects on yield under non-drought conditions. Loci associated with rate and/or duration of grain development were also identified. QTL analysis indicated many loci that were associated with both rate and duration of grain development. High rate and short duration of grain development were generally associated with larger seed size, but only two of these loci were associated with differences in stability of performance under drought., author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-448, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid230720ce-0e29-43da-99cc-102a7b79dc5a , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997). Water stress causes reduction in plant growth, impairment of photosynthesis and wilting by damaging carbon and nitrogen metabolism ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular BiologyrSpecial issue Cereal genomics, id ITEM-1, issue 5/6, issued date-parts 2002 , page 713-726, title Mapping QTLs associated with drought resistance in sorghum (Sorghum bicolor L. Moench), type article-journal, volume 48 , uris http//www.mendeley.com/documents/uuidd32b46f7-c950-4765-b4b5-eb0a3b53fedd , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b), manualFormatting (Sanchez et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sanchez et al., 2002). Water stress occurs at different stages of growth and adversely affects plant growth and yield parameters which lead to reduction in net yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family H. Kebede. P.K. Subudhi. D.T.Rosenow. H.T. Ngyen., given , non-dropping-particle , parse-names false, suffix , container-title Theoretical and Applied Genetics, id ITEM-1, issue 2-3, issued date-parts 2001 , page 266u2013276, title Quantitative trait loci influencing drought tolerance in grain sorghum (Sorghum bicolor L. Moench), type article-journal, volume 103 , uris http//www.mendeley.com/documents/uuid3487de59-fadf-4651-b15a-21a003d8fd47 , mendeley formattedCitation (H. Kebede. P.K. Subudhi. D.T.Rosenow. H.T. Ngyen., 2001), manualFormatting (Kebede et al., 2001), plainTextFormattedCitation (H. Kebede. P.K. Subudhi. D.T.Rosenow. H.T. Ngyen., 2001), previouslyFormattedCitation (H. Kebede. P.K. Subudhi. D.T.Rosenow. H.T. Ngyen., 2001) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Kebede et al., 2001). The extent of grain losses caused by drought stress vary with plant species and their stages of growth ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-1, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007), manualFormatting (Reddy et al., 2007), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2007). When water stress occurs at the seedling stage of crop development, plant establishment is affected ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid2ea7fd05-ae86-4f12-a8ed-b0a4d0fb2c02 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). When water stress occurs at pre-flowering period in barley and wheat for instance, grain fill phase is shortened and grain yield is reduced by decreasing the number of tillers, spike, grain per plant, grain weight and time to anthesisADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Nguyen, given H T, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2001 , page 266-267, title O R I G I N A L A RT I C L E Quantitative trait loci influencing drought tolerance in grain sorghum ( Sorghum bicolor L . Moench ), type article-journal , uris http//www.mendeley.com/documents/uuid2652d7c9-98bf-487d-b9e2-2a2cec5be817 , mendeley formattedCitation (H. T. Nguyen, 2001), manualFormatting (Nguyen, 2001), plainTextFormattedCitation (H. T. Nguyen, 2001), previouslyFormattedCitation (H. T. Nguyen, 2001) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Nguyen, 2001). Short duration water stress mostly reduces grain yield while prolonged water stress leads to complete death of plant ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq and Wahid, 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq and Wahid, 2009). Post-anthesis drought stress is considered more detrimental to grain yield regardless of the stress severity because photosynthesis per unit leaf area is decreased leading up to 70 yield losses ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family a, c Tadesse Yohannes, aMussie Weldetsion, aNegusse Abraha, dEric Manyasa, a, given bTesfamichael Abraha a, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 01, issued date-parts 2015 , page 1-8, title Journal of Plant Breeding and Genetics, type article-journal, volume 03 , uris http//www.mendeley.com/documents/uuid366d4eeb-505b-4f4f-b150-13942bd662c8 , mendeley formattedCitation (a, c Tadesse Yohannes, aMussie Weldetsion, aNegusse Abraha, dEric Manyasa, a, 2015), manualFormatting (Tadesse et al.,2015), plainTextFormattedCitation (a, c Tadesse Yohannes, aMussie Weldetsion, aNegusse Abraha, dEric Manyasa, a, 2015), previouslyFormattedCitation (a, c Tadesse Yohannes, aMussie Weldetsion, aNegusse Abraha, dEric Manyasa, a, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tadesse et al.,2015). As drought severity increases, photosynthesis is impaired due to a decline in RUBISCO activity which leads to reduction in grain size attributable to interruption of grain filling because of reduced level of sucrose synthase activity ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4161/psb.21949, author dropping-particle , family Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, given John Pichtel Aqil Ahmad, non-dropping-particle , parse-names false, suffix , container-title Plant Signalling and Behavior, id ITEM-1, issue August, issued date-parts 2017 , title Role of proline under changing environments Role of proline under changing environments A review, type article-journal, volume 2324 , uris http//www.mendeley.com/documents/uuid5bdeb828-da29-48b9-a98b-23f23a728e1e , mendeley formattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017), manualFormatting (Shamsul et al., 2017), plainTextFormattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017), previouslyFormattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Shamsul et al., 2017). Similarly, growth is constrained by the inactivation of adenosine glucose pyophysphorylation in wheat ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq anf Wahid, 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq anf Wahid, 2009) while in maize, water stress causes yield reduction by delaying silking which leads to increased anthesis to silking interval ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract The difficulty of choosing appropriate selection environments has restricted breeding progress for drought tolerance in highly-variable target environments. Genotype-by-environment interactions in southern African maize-growing environments result from factors related to maximum temperature, seasonal rainfall, season length, within season drought, subsoil pH and socio-economic factors that result in sub-optimal input application. In 1997 CIMMYT initiated a product-oriented breeding program targeted at improving maize for the drought-prone mid-altitudes of southern Africa. Maize varieties were selected in Zimbabwe using simultaneous selection in three types of environments, (i) recommended agronomic management/high rainfall conditions, (ii) low N stress, and (iii) managed drought. Between 2000 and 2002, 41 hybrids from this approach were compared with 42 released and prereleased hybrids produced by private seed companies in 36-65 trials across eastern and southern Africa. Average trial yields ranged from less than 1 t/ha to above 10 t/ha. Hybrids from CIMMYTs stress breeding program showed a consistent advantage over private company check hybrids at all yield levels. Selection differentials were largest between 2 to 5 t/ha and they became less significant at higher yield levels. An Eberhart-Russell stability analysis estimated a 40 yield advantage at the 1-ton yield level which decreased to 2.5 at the 10-ton yield level. We conclude that including selection under carefully managed high priority abiotic stresses, including drought, in a breeding program and with adequate weighing can significantly increase maize yields in a highly variable drought-prone environment and particularly at lower yield levels. Media summary A new maize breeding approach shows significant yield increases in drought-prone environments in southern Africa. Introduction Even though the challenge of developing drought tolerant crop varieties has generated an immense amount of literature, most practical breeding efforts remain focused on increasing productivity under favorable conditions where genetic variance, heritability and therefore breeding progress for grain yield are greatest. Apart from adapting crop phenology to rainfall patterns, multi-environment trials (METs) including trials grown under random drought conditions are often the only systematic approach exploited to increase yield stability of new crop varieties in drought-prone environments (e.g. Fukai et al. 1999 Shaku2026, author dropping-particle , family Bu00e4nziger, given Marianne, non-dropping-particle , parse-names false, suffix , dropping-particle , family Setimela, given Peter S, non-dropping-particle , parse-names false, suffix , dropping-particle , family Hodson, given David, non-dropping-particle , parse-names false, suffix , dropping-particle , family Vivek, given Bindiganavile, non-dropping-particle , parse-names false, suffix , container-title CDROM. Web site www.cropscience.org.au, id ITEM-1, issued date-parts 2004 , title Breeding for improved drought tolerance in maize adapted to southern Africa, type article-journal , uris http//www.mendeley.com/documents/uuid9bd9053a-766c-378b-b0e0-fa1cd2d9554b , mendeley formattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, 2004), manualFormatting (Bu00e4nziger et al., 2004), plainTextFormattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, 2004), previouslyFormattedCitation (Bu00e4nziger, Setimela, Hodson, Vivek, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Bnziger et al., 2004). Drought stress at flowering in maize usually leads to barrenness caused by reduction in the assimilate flux to the developing ear ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Neil De La Fuente, given Gerald, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Breeding Maize for Drought Tolerance Diversity Characterization and Linkage Disequilibrium of Maize Paralogs ZmLOX4 and ZmLOX5, type report , uris http//www.mendeley.com/documents/uuid1f0848e2-7e0a-3910-a718-c166858666a4 , mendeley formattedCitation (Neil De La Fuente, 2012), manualFormatting (Neil, 2012), plainTextFormattedCitation (Neil De La Fuente, 2012), previouslyFormattedCitation (Neil De La Fuente, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Neil, 2012). In sorghum, post flowering drought stress causes the susceptible genotypes to exhibit lodging, reduced seed size, susceptibility to charcoal rot, reduced biomass, loss of chlorophyll, degradation of photosynthesis, reduced seed weight, reduced grain number, reduced 100-seedwieghtand premature leaf and stalk senescence ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), manualFormatting (Sanchez1 et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sanchez1 et al., 2002). Post flowering stress affects transpiration efficiency, carbon dioxide fixation, carbohydrate translocation which ultimately lead to decreased photosynthate and reduced yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Morka., given Eyerusalem Arusi, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue June, issued date-parts 2015 , number-of-pages 5-70, title Physiological Indices for Drought Tolerance in Stay-green Sorghum (, type report , uris http//www.mendeley.com/documents/uuid2a1b438d-a114-431b-856b-6aac24e8ed2b , mendeley formattedCitation (Morka., 2015), plainTextFormattedCitation (Morka., 2015), previouslyFormattedCitation (Morka., 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Morka., 2015). Pre-flowering water stress of susceptible genotypes leads to leaf rolling, irregular leaf erectness, delayed flowering, floret abortion, reduced seed set, reduced panicle size, reduced plant height and premature plant death usually at grain fill phase in Sorghum ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family Nguyen, given P.K. Subudhi. D.T. Rosenow. H.T, non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid60445dda-f1f5-49ce-97d9-afb55d935112 , mendeley formattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), manualFormatting (Nguyen, 2000), plainTextFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), previouslyFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Nguyen, 2000). Sorghum genotypes respond to drought stress through different genetic mechanisms involving adjustments at the level of morphology, phenology, physiology and biochemistry ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A. Mafakheri1, A. Siosemardeh1, B. Bahramnejad1, P.C. Struik2, given Y. Sohrabi1 1Department, non-dropping-particle , parse-names false, suffix , container-title Australian Journal of Crop Science, id ITEM-1, issue 8, issued date-parts 2010 , page 580-585, title Effect of drought stress on yield , proline and chlorophyll contents in three chickpea cultivars, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuid81d536d6-145b-47e7-b0d5-dd4e856dc1bc , mendeley formattedCitation (A. Mafakheri1, A. Siosemardeh1, B. Bahramnejad1, P.C. Struik2, 2010), manualFormatting (Mafakheri et al., 2010), plainTextFormattedCitation (A. Mafakheri1, A. Siosemardeh1, B. Bahramnejad1, P.C. Struik2, 2010), previouslyFormattedCitation (A. Mafakheri1, A. Siosemardeh1, B. Bahramnejad1, P.C. Struik2, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Mafakheri et al., 2010). The timing and intensity of the stress plays a vital role in determining the sequence of plant responses contributing to large genotype by environment interaction ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development , leaf anatomy , root growth , and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid649ca0af-e5b0-420e-bd9f-49917641ce2f , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Total drought resistance in plants is due to both drought stress avoidance and tolerance mechanisms ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract Before attempting to address this subject it isnimportant to define what is understood by temperaturenstress. It is a complex subject which hasnrecently been reviewed in three books (Lyons etnal. 1979 Levitt 1980 Turner and Kramer 1980)ntherefore definitions and details of the physiologicalnand biochemical processes associated withntemperature stress will not be given here. In brief,nhowever, a quantitative definition of temperaturenstress in sorghum, as in any crop, is difficult tonprovide since it will depend on a number of factorsnich will include the duration of exposure ofneither high or low temperature, the activity ornstage of growth of the exposed tissue and finallynthe thermal adaptation of the particular sorghumncultivar., author dropping-particle , family Peacock, given J M, non-dropping-particle , parse-names false, suffix , container-title International Crops Research lnstltute for the Semi-Arid Tropics 1982 Sorghum in the Eighties Proceedings of the International Symposium on Sorghum, id ITEM-1, issued date-parts 1982 , page 143-158, title Response and Tolerance of Sorghum to Temperature Stress, type article-journal , uris http//www.mendeley.com/documents/uuidd606494b-5b15-4483-b0ef-0eeadc4d3f04 , mendeley formattedCitation (Peacock, 1982), plainTextFormattedCitation (Peacock, 1982), previouslyFormattedCitation (Peacock, 1982) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Peacock, 1982). Drought avoidance and escape mechanisms (earliness) are key water tolrance traits which have been well studied and categorized ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Reddy, given V Gopal, non-dropping-particle , parse-names false, suffix , dropping-particle , family Upadhyaya, given H D, non-dropping-particle , parse-names false, suffix , dropping-particle , family Gowda, given C L L, non-dropping-particle , parse-names false, suffix , container-title Organization, id ITEM-1, issue 1, issued date-parts 2006 , page 9-13, title Current Status of Sorghum Genetic Resources at ICRISAT Their Sharing and Impacts, type article-journal, volume 2 , uris http//www.mendeley.com/documents/uuidea597706-7b11-4a43-a0bb-bac13efbd4ec , mendeley formattedCitation (Reddy, Upadhyaya, Gowda, 2006), manualFormatting (Reddy et al., 2006), plainTextFormattedCitation (Reddy, Upadhyaya, Gowda, 2006), previouslyFormattedCitation (Reddy, Upadhyaya, Gowda, 2006) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2006). 2.5 Sorghum drought tolerance mechanisms. 2.5.1 Drought escape Drought escapes is defined as the plant ability to reach their vital stage of life cycle before stress commences ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). Plants escape drought stress by making good use of optimal conditions available at the beginning of cropping season to develop vigor required to complete the lifecycle ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2134/agronj2009.0465, ISSN 00021962, abstract Post-flowering drought tolerance is an essential trait for increasing the production of sorghum Sorghum bicolor (L.) Moench and other cereals in Mediterranean and semiarid tropical climates. Current methodologies for identifying the nonsenescent (stay-green) trait require the right intensity of drought stress at the right developmental stage to visually evaluate lines in the field. Field-based evaluations of drought tolerance are notoriously difficult to manage, and often require growing lines in multiple locations across several years to acquire a meaningful assessment of the stay-green trait. By means of a 30-min high-temperature challenge to leaf tissue during flowering of well-watered sorghum and a 30-min room temperature recovery, we show that stay-green lines can be readily identified. Using chlorophyll fluorescence to monitor tissue injury, we found that tissue with higher intercellular sucrose concentrations exhibited higher chlorophyll fluorescence yield following the temperature challenge. Stay-green lines evaluated in this study maintained higher dawn leaf sucrose levels than the senescent lines among the five youngest leaf positions. Evaluation of 10 known stay-green and senescent sorghum lines, previously reported in the literature, with this bioassay allowed us to separate the two classes of sorghum from well-watered flowering plants. The stay-green lines can also be separated from senescent lines under well-watered greenhouse conditions from the boot stage onward. This technology will greatly reduce the selection time needed to identify drought tolerant sorghum., author dropping-particle , family J. J. Burke, C. D. Franks, G. Burow, given and Z. Xin ABSTRACT, non-dropping-particle , parse-names false, suffix , container-title Agronomy Journal, id ITEM-1, issue 4, issued date-parts 2010 , page 1118-1122, title Selection system for the stay-green drought tolerance trait in sorghum germplasm, type article-journal, volume 102 , uris http//www.mendeley.com/documents/uuid29c1602d-bdd7-4c52-81e7-1dbe5ef123ce , id ITEM-2, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-2, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012 J. J. Burke, C. D. Franks, G. Burow, 2010), manualFormatting (Acquaah et al., 2012 Burke et al., 2010), plainTextFormattedCitation (George, 2012 J. J. Burke, C. D. Franks, G. Burow, 2010), previouslyFormattedCitation (George, 2012 J. J. Burke, C. D. Franks, G. Burow, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012 Burke et al., 2010). Drought escape genotypes do exhibit essential morphological modifications that enhance water use efficiency (WUE) as well as rapid phenological development and development plasticity to escape stress periods ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Rao, given R C N, non-dropping-particle , parse-names false, suffix , dropping-particle , family Nigam, given S N, non-dropping-particle , parse-names false, suffix , container-title Management of Agricultural Drought – Agronomic and Genetic Options, id ITEM-1, issued date-parts 2003 , page 123-141, title Genetic Options for Drought Management in Groundnut, type article , uris http//www.mendeley.com/documents/uuidf79027d6-6059-42c6-a386-0e05395a74ec , mendeley formattedCitation (Rao Nigam, 2003), manualFormatting (Rao and Nigam, 2003), plainTextFormattedCitation (Rao Nigam, 2003), previouslyFormattedCitation (Rao Nigam, 2003) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rao and Nigam, 2003). 2.5.2 Drought avoidance Drought avoidance is the ability of plant to prevent decrease of water potential under drought stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework et al., 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012). Plants avoid drought by maximizing water uptake at the roots and making good use of water by minimizing stomatal water losses ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Larry, Gene, given Balko., non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1975 , title YIELD AND QUALITY OF SORGHUM GENOTYPES goS, type article-journal , uris http//www.mendeley.com/documents/uuidaaae6e2b-f0fe-4bb5-b4b6-c7a3824aaba4 , id ITEM-2, itemData author dropping-particle , family Taye Tadesse1 , given Tesfaye Tesso1 and Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , container-title An Open Access Journal published by ICRISAT, id ITEM-2, issue December, issued date-parts 2008 , page 2-7, title Combining ability of introduced sorghum parental lines for major morpho-agronomic traits, type article-journal, volume 6 , uris http//www.mendeley.com/documents/uuid4f396616-4dde-4ddd-9ac9-9390ccabd1e5 , mendeley formattedCitation (Larry, Gene, 1975 Taye Tadesse1 , 2008), manualFormatting (Balko et al., 1975 Tadesse et al., 2008), plainTextFormattedCitation (Larry, Gene, 1975 Taye Tadesse1 , 2008), previouslyFormattedCitation (Larry, Gene, 1975 Taye Tadesse1 , 2008) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Balko et al., 1975 Tadesse et al., 2008). Avoidance can be either water conservation mechanism if the plant uses C4 photosynthetic pathways or water uptake mechanisms if the plant develops deep root system which enhances plant reach to underground water resources ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Tesfamichael, given , non-dropping-particle , parse-names false, suffix , container-title Science, id ITEM-1, issued date-parts 1999 , title for Traits Related To Drought Resistance Selection Methods and Genetic Variability for Traits Related To Drought Resistance, type article-journal , uris http//www.mendeley.com/documents/uuid08d947ad-c318-4b72-b38a-6905e8cc6601 , mendeley formattedCitation (Tesfamichael, 1999), plainTextFormattedCitation (Tesfamichael, 1999), previouslyFormattedCitation (Tesfamichael, 1999) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tesfamichael, 1999). Genotypes that use water conservation mechanisms do exhibit specialized morphological adaptations including increased stomatal, cuticular resistant and reduced leaf growth in a bid to mitigate water losses whereas genotypes that use collection mechanism do exhibit extended root growth ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, author dropping-particle , family Staggenborg, given Scott, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July 2015, issued date-parts 2010 , title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal , uris http//www.mendeley.com/documents/uuid0f41d9fc-2205-4045-a325-c02fa956d48e , mendeley formattedCitation (S. Staggenborg, 2010), manualFormatting (Staggenborg, 2010), plainTextFormattedCitation (S. Staggenborg, 2010), previouslyFormattedCitation (S. Staggenborg, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Staggenborg, 2010). 2.5.3 Drought recovery The ability of sorghum plants to recover from drought depends on the severity of the wter stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1371/journal.pone.0154423, author dropping-particle , family Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, given Giles N. Johnson1, non-dropping-particle , parse-names false, suffix , container-title PLoS ONE, id ITEM-1, issued date-parts 2016 , page 1-20, title Biochemical Analyses of Sorghum Varieties Reveal Differential Responses to Drought, type article-journal , uris http//www.mendeley.com/documents/uuid61497594-2ac3-4b57-98e6-0f55777783cf , mendeley formattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), manualFormatting (Ogbaga et al., 2016), plainTextFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), previouslyFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ogbaga et al., 2016). Severe wter stress impairs wter absorption and transport which inhibits post-drought stress recovery ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1371/journal.pone.0154423, author dropping-particle , family Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, given Giles N. Johnson1, non-dropping-particle , parse-names false, suffix , container-title PLoS ONE, id ITEM-1, issued date-parts 2016 , page 1-20, title Biochemical Analyses of Sorghum Varieties Reveal Differential Responses to Drought, type article-journal , uris http//www.mendeley.com/documents/uuid61497594-2ac3-4b57-98e6-0f55777783cf , mendeley formattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), manualFormatting (Ogbaga et al., 2016), plainTextFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), previouslyFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ogbaga et al., 2016). Drought stress impairs warer intake by altering the root function and structural configuration of the root plasma membrane which leads to reduced stomatal opening and reduced transpiration rate due to reduced stomatal area ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A. Bibi, H. A. Sadaqat, given M. H. N. Tahir and H. M. Akram, non-dropping-particle , parse-names false, suffix , container-title The Journal of Animal and Plant Sciences, id ITEM-1, issue 3, issued date-parts 2012 , page 2-8, title SCREENING OF SORGHUM ( Sorghum bicolor Var Moench ) FOR DROUGHT TOLERANCE AT SEEDLING STAGE IN POLYETHYLENE GLYCOL ., type article-journal, volume 22 , uris http//www.mendeley.com/documents/uuidbcb66e08-f58a-4e4a-bd5b-6461ae46e630 , id ITEM-2, itemData DOI 10.1371/journal.pone.0154423, author dropping-particle , family Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. 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Ellis3, Royston Goodacre3, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ogbaga et al., 2016 Sadaqat et al., 2012). As the wter stress severity spins and excedes critical wter potential, inhibition of intake of wter and inorganic ion solutes esential for osmoregualtion occurs leading to wilting and plant death ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5829/idosi.aejaes.2013.13.10.11045, author dropping-particle , family Moslem Abdipur, Hamid Reza Ramezani, given Vahid Bavei and Sajad Talaee, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 10, issued date-parts 2013 , page 1325-1338, title Effectiveness of Canopy Temperature and Chlorophyll Content Measurements at Different Plant Growth Stages for Screening of Drought Tolerant Wheat Genotype s, type article-journal, volume 13 , uris http//www.mendeley.com/documents/uuid1bf5db1d-b087-4559-8b47-798f8ca5f5cf , mendeley formattedCitation (Moslem Abdipur, Hamid Reza Ramezani, 2013), manualFormatting (Abdipur et al., 2013), plainTextFormattedCitation (Moslem Abdipur, Hamid Reza Ramezani, 2013), previouslyFormattedCitation (Moslem Abdipur, Hamid Reza Ramezani, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Abdipur et al., 2013). The second way through which drought stress affects plant recovery ability is by impairing photosynthesis through photo-inhinbition in the reaction centres of wter stress sensitive photosystem II ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1371/journal.pone.0154423, author dropping-particle , family Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, given Giles N. Johnson1, non-dropping-particle , parse-names false, suffix , container-title PLoS ONE, id ITEM-1, issued date-parts 2016 , page 1-20, title Biochemical Analyses of Sorghum Varieties Reveal Differential Responses to Drought, type article-journal , uris http//www.mendeley.com/documents/uuid61497594-2ac3-4b57-98e6-0f55777783cf , mendeley formattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), manualFormatting (Ogbaga et al., 2016), plainTextFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016), previouslyFormattedCitation (Chukwuma C. Ogbaga1u00a4a, Piotr Stepien1, 2, Beth C. Dyson1, 3u00a4b, Nicholas J. W. Rattray3, David I. Ellis3, Royston Goodacre3, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ogbaga et al., 2016). Plants that recover from wter stress do exhibit functional staygreen adaptations and functions including functioning phtosynthetic machinery, effeicient photosysntstem II , intact electron transport chain and high level of storage sugar which acts as osmolytes by ensurring cell membrane stability to prevent photoinhibition and cell bleaching ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789157685063, author dropping-particle , family Motlhaodi, given Tiny Mpho, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2016 , title Genetic Diversity and Nutritional Content of Sorghum Sorghum bicolor ( L .) Moench Accessions from Southern Africa Tiny Mpho Motlhaodi, type book , uris http//www.mendeley.com/documents/uuid987d5120-aac9-46a8-936c-927f45b5a437 , mendeley formattedCitation (Motlhaodi, 2016), plainTextFormattedCitation (Motlhaodi, 2016), previouslyFormattedCitation (Motlhaodi, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Motlhaodi, 2016). 2.5.4 Drought tolerance Drought avoidance is the plant ability to survive low tissue water content in drought stress condition ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract Before attempting to address this subject it isnimportant to define what is understood by temperaturenstress. It is a complex subject which hasnrecently been reviewed in three books (Lyons etnal. 1979 Levitt 1980 Turner and Kramer 1980)ntherefore definitions and details of the physiologicalnand biochemical processes associated withntemperature stress will not be given here. In brief,nhowever, a quantitative definition of temperaturenstress in sorghum, as in any crop, is difficult tonprovide since it will depend on a number of factorsnich will include the duration of exposure ofneither high or low temperature, the activity ornstage of growth of the exposed tissue and finallynthe thermal adaptation of the particular sorghumncultivar., author dropping-particle , family Peacock, given J M, non-dropping-particle , parse-names false, suffix , container-title International Crops Research lnstltute for the Semi-Arid Tropics 1982 Sorghum in the Eighties Proceedings of the International Symposium on Sorghum, id ITEM-1, issued date-parts 1982 , page 143-158, title Response and Tolerance of Sorghum to Temperature Stress, type article-journal , uris http//www.mendeley.com/documents/uuidd606494b-5b15-4483-b0ef-0eeadc4d3f04 , mendeley formattedCitation (Peacock, 1982), plainTextFormattedCitation (Peacock, 1982), previouslyFormattedCitation (Peacock, 1982) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Peacock, 1982). The fundamental basis of drought tolerance is staygreen trait which enhances plant growth and reproduction under drought stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Walulu, given Richard Sikuku, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1991 , title GENETIC CONTROL OF POST-FLOWERING DROUGHT TOLERANCE ( STAY GREEN ) IN SORGHUM by IN Submitted to the Graduate Faculty of Texas Tech University in Part i a 1 F u 1 f i 11 men t of the Requirements for the Degree of HASTER OF SCIENCE Approved, type article-journal , uris http//www.mendeley.com/documents/uuid9dc708ca-7067-406a-995a-2b7188df49f0 , mendeley formattedCitation (Walulu, 1991), manualFormatting (Walulu, 1991 Staggenborg, 2010), plainTextFormattedCitation (Walulu, 1991), previouslyFormattedCitation (Walulu, 1991) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Walulu, 1991 Staggenborg, 2010). 2.5.4.1 Staygreen trait Staygreen is defined as an enhanced foliar greenness during graining fill phase to physiological maturity under post anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), manualFormatting (Rosenow et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rosenow et al., 2002). Staygreen is an important trait associated with drought tolerance in several plants including sorghum crop ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4, given David R. Jordan1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Hammer2, given Patricia E. Klein5 and Graeme L., non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2014 , page 817-830, title Stay-green alleles individually enhance grain yield in sorghum under drought by modifying canopy development and water uptake patterns, type article-journal , uris http//www.mendeley.com/documents/uuiddd3081ad-71c8-4721-ae5c-af5412321ea0 , mendeley formattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014), previouslyFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Staygreen trait enhances disease resistance and reduces severity of lodging ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , id ITEM-2, itemData author dropping-particle , family Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4, given David R. Jordan1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Hammer2, given Patricia E. Klein5 and Graeme L., non-dropping-particle , parse-names false, suffix , id ITEM-2, issued date-parts 2014 , page 817-830, title Stay-green alleles individually enhance grain yield in sorghum under drought by modifying canopy development and water uptake patterns, type article-journal , uris http//www.mendeley.com/documents/uuiddd3081ad-71c8-4721-ae5c-af5412321ea0 , mendeley formattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012), manualFormatting (Borrell et al., 2014 Dalal, 2012), plainTextFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012), previouslyFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Dalal, 2012). Similarly, staygreen loci play key roles in source – sink reduction by reducing canopy size through reduced tillering, increased size of lower leaves, reduced size of upper leaves and reduction of number of leave per culm which minimize transpiration water loss and water demanding sink-sources ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2011Thomas and Ougham, 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2011Thomas and Ougham, 2014). Staygreen trait improved yield and yield components under post anthesis drought stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2135/cropsci2000.4041026x, author dropping-particle , family Borrell, given Andrew, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July, issued date-parts 2000 , title Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought I . Leaf Growth and Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought , type article-journal , uris http//www.mendeley.com/documents/uuid65dd2e28-15d2-480e-bcaa-58f578012f0b , mendeley formattedCitation (A. Borrell, 2000), manualFormatting (Borrell, 2000), plainTextFormattedCitation (A. Borrell, 2000), previouslyFormattedCitation (A. Borrell, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell, 2000). The trait improves grain yield by increasing grain number per panicle and 100-seed weight ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2134/advagricsystmodel1.c11, ISBN 978-0-89118-167-5, ISSN 2163-2790, abstract Drought and heat stress are among the two most important environmen- tal factors influencing crop growth, development, and yield processes. A comprehensive understanding of the impact of drought and heat stress will be critical in evaluating the impact of climate change and climate variabil- ity on crop production. Both drought and heat stress influence an array of processes including physiological, growth, developmental, yield, and qual- ity of crop. The objective of this review is to provide an overview of the influences of these two stresses on the above processes independently and in combination. Our review suggests a clear need of information on interactive effects of stresses particularly of drought and heat stress which mostly occur in combination. Both short- and long-term stresses can signifi- cantly influence growth and yield processes when stress occurs at sensitive stages. Crops are generally more sensitive to drought and/or heat stress during reproductive stages of development, which mainly influences seed numbers. Some of the important traits associated with drought- and/or heat-stress tolerance are indicated and discussed. The impacts of drought and heat stress are often different, and tolerance mechanisms may also be different. There is a wide range of crop modeling approaches (simple empirical models and more mechanistic models) that try to quantify the impact of stresses on growth, development, and yield and yield quality traits. These crop models should have the capability to quantify the impact of both short- and long-term stress events on growth, development, and yield processes. Modeling growth, development, sink-source relation, grain yield, and grain quality of crops can improve understanding of physi- ological and genetic nature of tolerance which can lead to increased grain yield and quality of crops. Improved models can enhance our capacity to predict crop performance in future climates and also to identify traits that can potentially be improved or exploited to obtain higher and more stable crop yields under stressed environments., author dropping-particle , family Staggenborg, given P. V. V. Prasad and S. A., non-dropping-particle , parse-names false, suffix , container-title Kanas Sate University, id ITEM-1, issued date-parts 2008 , page 301-356, title Impacts of Drought and/or Heat Stress on Physiological, Developmental, Growth, and Yield Processes of Crop Plants, type article-journal , uris http//www.mendeley.com/documents/uuid38cf3613-b8b8-4bb7-82c7-3f6670a9cf1c , mendeley formattedCitation (P. V. V. P. and S. A. Staggenborg, 2008), manualFormatting (Prasad et al., 2008), plainTextFormattedCitation (P. V. V. P. and S. A. Staggenborg, 2008), previouslyFormattedCitation (P. V. V. P. and S. A. Staggenborg, 2008) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Prasad et al., 2008). The better yield performance among staygreen genotypes is due in part to their high efficiency in converting absorbed water into biomass and grain yield as well as sustained photosynthate flow through sustained stability of chloroplast and photosynthetic machinery under stress condition ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erl225, author dropping-particle , family Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, given Robert Klein7 and John Mullet1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 2, issued date-parts 2018 , page 327-338, title Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence, type article-journal, volume 58 , uris http//www.mendeley.com/documents/uuid074f286e-a9c2-4331-81ad-947594116eac , mendeley formattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018), manualFormatting (Beyene et al., 2015 Borrell, 2000 Tesfamichael et al., 2015 Harris et al., 2018), plainTextFormattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018), previouslyFormattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Borrell, 2000 Tesfamichael et al., 2015 Harris et al., 2018). Staygreen is expressed as functional or cosmetic ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (Thomas Ougham, 2014a), manualFormatting (Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014a), previouslyFormattedCitation (Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Thomas and Ougham, 2014). Functional staygreen is an important economic trait that allows for maintenance of photosynthetic activities in waterstress conditions. Functional staygreen is manifested as staygreen type A, B and E ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , id ITEM-2, itemData author dropping-particle , family Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., given Subhash Bharani and Vinayak Turaidar, non-dropping-particle , parse-names false, suffix , container-title Int. J. Pure App. Biosci., id ITEM-2, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid69473559-95d1-411c-87d6-aa2627b99dc0 , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), manualFormatting (Dalawai, 2017 Rosenow et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalawai, 2017 Rosenow et al., 2002). Cosmetic staygreen is of no economic value and is characterised by impaired photosynthetic capacity and chlorophyll pigment retention in already senesced leaves of the plant ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , id ITEM-2, itemData author dropping-particle , family Dalawai, given Ningaraj, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid59f72db8-f048-43ae-90ac-494ca55d53a7 , id ITEM-3, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-3, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Dalawai, 2017 Thomas Ougham, 2014a), manualFormatting (Dalawai, 2017b Rosenow et al., 2002 Thomas and Ougham, 2014), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Dalawai, 2017 Thomas Ougham, 2014a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a Dalawai, 2017 Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalawai, 2017b Rosenow et al., 2002 Thomas and Ougham, 2014). Cosmetic staygreen is expressed as staygreen type C and D ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., given Subhash Bharani and Vinayak Turaidar, non-dropping-particle , parse-names false, suffix , container-title Int. J. Pure App. Biosci., id ITEM-1, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid69473559-95d1-411c-87d6-aa2627b99dc0 , mendeley formattedCitation (Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), manualFormatting (Krupa et al., 2017), plainTextFormattedCitation (Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), previouslyFormattedCitation (Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Krupa et al., 2017). The clear distinctive differences between functional and cosmetic staygreen are that functional staygreen is associated with delayed transition from carbon-capture to nitrogen-remobilization phase of plant development while cosmetic staygreen does not delay this transition phase (ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (Thomas Ougham, 2014a), manualFormatting Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014a), previouslyFormattedCitation (Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Thomas and Ougham, 2014). Functional staygreen is associated with high green leaf area duration (GLAD) at physiological maturity unlike cosmetic staygreen ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (Thomas Ougham, 2014a), manualFormatting (Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014a), previouslyFormattedCitation (Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Thomas and Ougham, 2014). Functional staygreen is positively correlated with xylem pressure potential and grain yield which results in prolonged high water potential, green leaf duration at maturity (GlAM) and sustained photosynthetic activities unlike cosmetic staygreen ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/A1009673126345, ISBN 1380-3743, ISSN 13803743, abstract Drought is a serious agronomic problem and the single greatest factor contributing to crop yield loss in the world today. This problem may be alleviated by developing crops that are well adapted to dry-land environments. Sorghum (Sorghum bicolor (L.) Moench) is one of the most drought-tolerant grain crops and is an excellent crop model for evaluating mechanisms of drought tolerance. In this study, a set of 98 recombinant inbred (RI) sorghum lines was developed from a cross between two genotypes with contrasting drought reactions, TX7078 (pre-flowering-tolerant, post-flowering susceptible) and B35 (pre-flowering susceptible, post-flowering-tolerant). The RI population was characterized under drought and non-drought conditions for the inheritance of traits associated with post-flowering drought tolerance and for potentially related components of grain development. Quantitative trait loci (QTL) analysis identified 13 regions of the genome associated with one or more measures of post-flowering drought tolerance. Two QTL were identified with major effects on yield and staygreen under post-flowering drought. These loci were also associated with yield under fully irrigated conditions suggesting that these tolerance loci have pleiotropic effects on yield under non-drought conditions. Loci associated with rate and/or duration of grain development were also identified. QTL analysis indicated many loci that were associated with both rate and duration of grain development. High rate and short duration of grain development were generally associated with larger seed size, but only two of these loci were associated with differences in stability of performance under drought., author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-448, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid230720ce-0e29-43da-99cc-102a7b79dc5a , id ITEM-2, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997 Thomas Ougham, 2014a), manualFormatting (Thomas and Ougham, 2014), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997 Thomas Ougham, 2014a), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997 Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Thomas and Ougham, 2014). 2.5.4.1.1 Genetic basis of stay green Staygreen trait is governed by a major gene ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Walulu, given Richard Sikuku, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1991 , title GENETIC CONTROL OF POST-FLOWERING DROUGHT TOLERANCE ( STAY GREEN ) IN SORGHUM by IN Submitted to the Graduate Faculty of Texas Tech University in Part i a 1 F u 1 f i 11 men t of the Requirements for the Degree of HASTER OF SCIENCE Approved, type article-journal , uris http//www.mendeley.com/documents/uuid9dc708ca-7067-406a-995a-2b7188df49f0 , mendeley formattedCitation (Walulu, 1991), plainTextFormattedCitation (Walulu, 1991), previouslyFormattedCitation (Walulu, 1991) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Walulu, 1991). Recent advances in genetic mapping have discovered four main staygreen quantitative trait loci (QTLs) namely Stg2, Stg1, Stg3 and Stg4 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family Nguyen, given P.K. Subudhi. D.T. Rosenow. H.T, non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid60445dda-f1f5-49ce-97d9-afb55d935112 , mendeley formattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), manualFormatting (Subudhi et al., 2000), plainTextFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), previouslyFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000). These staygreen QTLs confer staygreen trait, earliness and yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular BiologyrSpecial issue Cereal genomics, id ITEM-1, issue 5/6, issued date-parts 2002 , page 713-726, title Mapping QTLs associated with drought resistance in sorghum (Sorghum bicolor L. Moench), type article-journal, volume 48 , uris http//www.mendeley.com/documents/uuidd32b46f7-c950-4765-b4b5-eb0a3b53fedd , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015 Sanchez et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Sanchez et al., 2002). The staygreen QTLs also account for 84 of phenotypic variation exhibited by staygreen genotypes ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family P.K. Subudhi. D.T. Rosenow. H.T Nguyen, given , non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid4e66a521-69c9-444b-91a0-85a900983ab6 , mendeley formattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), manualFormatting (Subudhi et al., 2000), plainTextFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), previouslyFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000). QTLs for stg1 and stg2 loci have been mapped to linkage A while stg3 and stg4 loci were mapped onto linkage group D and J ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family P.K. Subudhi. D.T. Rosenow. H.T Nguyen, given , non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid4e66a521-69c9-444b-91a0-85a900983ab6 , mendeley formattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), manualFormatting (Subudhi et al., 2000), plainTextFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), previouslyFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000). 2.5.4.1.2 Screening techniques for stay green Direct and indirect selection approaches have been widely used as staygreen screening techniques. Direct approaches use environmental conditions in which the onset of stress factors is uniform and predictable whereas indirect ones use well managed and stress environments ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5829/idosi.aejaes.2013.13.10.11045, author dropping-particle , family Moslem Abdipur, Hamid Reza Ramezani, given Vahid Bavei and Sajad Talaee, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 10, issued date-parts 2013 , page 1325-1338, title Effectiveness of Canopy Temperature and Chlorophyll Content Measurements at Different Plant Growth Stages for Screening of Drought Tolerant Wheat Genotype s, type article-journal, volume 13 , uris http//www.mendeley.com/documents/uuid1bf5db1d-b087-4559-8b47-798f8ca5f5cf , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013), manualFormatting (Abdipur et al., 2013 Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Abdipur et al., 2013 Beyene et al., 2015). Selection under both optimal and drought conditions represent the ideal screening approach for yield and yield stability ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/A1009673126345, ISBN 1380-3743, ISSN 13803743, abstract Drought is a serious agronomic problem and the single greatest factor contributing to crop yield loss in the world today. This problem may be alleviated by developing crops that are well adapted to dry-land environments. Sorghum (Sorghum bicolor (L.) Moench) is one of the most drought-tolerant grain crops and is an excellent crop model for evaluating mechanisms of drought tolerance. In this study, a set of 98 recombinant inbred (RI) sorghum lines was developed from a cross between two genotypes with contrasting drought reactions, TX7078 (pre-flowering-tolerant, post-flowering susceptible) and B35 (pre-flowering susceptible, post-flowering-tolerant). The RI population was characterized under drought and non-drought conditions for the inheritance of traits associated with post-flowering drought tolerance and for potentially related components of grain development. Quantitative trait loci (QTL) analysis identified 13 regions of the genome associated with one or more measures of post-flowering drought tolerance. Two QTL were identified with major effects on yield and staygreen under post-flowering drought. These loci were also associated with yield under fully irrigated conditions suggesting that these tolerance loci have pleiotropic effects on yield under non-drought conditions. Loci associated with rate and/or duration of grain development were also identified. QTL analysis indicated many loci that were associated with both rate and duration of grain development. High rate and short duration of grain development were generally associated with larger seed size, but only two of these loci were associated with differences in stability of performance under drought., author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-448, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid230720ce-0e29-43da-99cc-102a7b79dc5a , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997). To achieve this, both visual scoring of leaf and plant senescence and genomic tools such as marker assisted selection (MAS) can be used to select for ideal staygreen genotypes ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1186/1471-2164-15-909, ISBN 1471-2164, ISSN 14712164, PMID 25326366, abstract BACKGROUND Sorghum Sorghum bicolor (L.) Moench is an important dry-land cereal of the world providing food, fodder, feed and fuel. Stay-green (delayed-leaf senescence) is a key attribute in sorghum determining its adaptation to terminal drought stress. The objective of this study was to validate sorghum stay-green quantitative trait loci (QTL) identified in the past, and to identify new QTL in the genetic background of a post-rainy adapted genotype M35-1.nnRESULTS A genetic linkage map based on 245 F9 Recombinant Inbred Lines (RILs) derived from a cross between M35-1 (more senescent) and B35 (less senescent) with 237 markers consisting of 174 genomic, 60 genic and 3 morphological markers was used. The phenotypic data collected for three consecutive post-rainy crop seasons on the RIL population (M35-1 u00d7 B35) was used for QTL analysis. Sixty-one QTL were identified for various measures of stay-green trait and each trait was controlled by one to ten QTL. The phenotypic variation explained by each QTL ranged from 3.8 to 18.7. Co-localization of QTL for more than five traits was observed on two linkage groups i.e. on SBI-09-3 flanked by S18 and Xgap206 markers and, on SBI-03 flanked by XnhsbSFCILP67 and Xtxp31. QTL identified in this study were stable across environments and corresponded to sorghum stay-green and grain yield QTL reported previously. Of the 60 genic SSRs mapped, 14 were closely linked with QTL for ten traits. A genic marker, XnhsbSFCILP67 (Sb03g028240) encoding Indole-3-acetic acid-amido synthetase GH3.5, was co-located with QTL for GLB, GLM, PGLM and GLAM on SBI-03. Genes underlying key enzymes of chlorophyll metabolism were also found in the stay-green QTL regions.nnCONCLUSIONS We validated important stay-green QTL reported in the past in sorghum and detected new QTL influencing the stay-green related traits consistently. Stg2, Stg3 and StgB were prominent in their expression. Collectively, the QTL/markers identified are likely candidates for subsequent verification for their involvement in stay-green phenotype using NILs and to develop drought tolerant sorghum varieties through marker-assisted breeding for terminal drought tolerance in sorghum., author dropping-particle , family Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, given Seetharama Nadoor1 and Jagannatha Vishnu Patil, non-dropping-particle , parse-names false, suffix , container-title BMC Genomics, id ITEM-1, issue 1, issued date-parts 2014 , title Detection and validation of stay-green QTL in post-rainy sorghum involving widely adapted culti M35-1 and a popular stay-green genotype B35, type article-journal, volume 15 , uris http//www.mendeley.com/documents/uuid6b398253-a8ec-40b3-960b-6b154c4c4c70 , mendeley formattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014), manualFormatting (Reddy et al., 2014), plainTextFormattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014), previouslyFormattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2014). Marker assisted selection (MAS) is more efficient, less time and resource consuming than conventional breeding approach ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Selection in either of the screening technique should always factor in yield and yield components to disprove of the concept that staygreen may be correlated with low yield attributed to low sink-source under post anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , id ITEM-2, itemData DOI 10.1017/S1479262115000696, ISSN 1479263X, abstract Hybrid breeding relies on selection of genetically unrelated and complementary parents for key traits. The objective of this study was to examine genetic variation and identify unique sorghum genotypes using phenotypic and simple sequence repeat (SSR) markers and to determine their relationships with combining ability and heterosis for grain yield. A total of 32 landraces and four cytoplasmic male sterile (CMS) lines were phenotyped using 25 agro-morphological traits and genotyped with 30 polymorphic SSR markers. The landraces were crossed with four CMS lines using a line u00d7 tester mating design. The 128 hybrids, 36 parentals and four check varieties were field-evaluated using a 12 u00d7 14 alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield were determined. Genetic distance estimates ranged from 0.39 to 0.60 and 0.50 to 0.79, based on phenotypic and SSR markers, respectively. Landraces 72572, 75454, 200654, 239175, 239208, 244735A and 242039B and CMS lines ICSA 743 and ICSA 756 displayed positive and significant GCA effects for grain yield. Based on the SCA effects of yield, lines were classified into three heterotic groups aligned to the different cytoplasmic systems of testers. Lines with high GCA effects rendered hybrids with highly significant SCA effects with high mid-parent heterosis (MPH) for grain yield. Both marker systems were effective in demarcating sorghum genotypes that provided desirable cross-combinations with high combining ability effects and MPH for grain yield. The selected genotypes are recommended as potential parents for sorghum hybrid breeding in moisture stress environments., author dropping-particle , family Beyene Amelework, given Hussien Shimelis and Mark Laing, non-dropping-particle , parse-names false, suffix , dropping-particle , family African Center for Crop Improvement, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, given South Africa, non-dropping-particle , parse-names false, suffix , dropping-particle , family Received, given , non-dropping-particle , parse-names false, suffix , container-title Plant Genetic Resources Characterisation and Utilisation, id ITEM-2, issue 4, issued date-parts 2017 , page 335-347, title Genetic variation in sorghum as revealed by phenotypic and SSR markers Implications for combinng ability and heterosis for grain yield, type article-journal, volume 15 , uris http//www.mendeley.com/documents/uuid1396b5ac-7e1d-4f77-b191-777bcc46b356 , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework, African Center for Crop Improvement, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, Received, 2017), manualFormatting (Borrell et al., 2014 Beyene et al., 2015 Amelework et al., 2017), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework, African Center for Crop Improvement, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, Received, 2017), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework, African Center for Crop Improvement, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, Received, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Beyene et al., 2015 Amelework et al., 2017). Selection may also be done at plant growth phase at which they are more susceptible to waterstress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-1, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007), manualFormatting (Reddy et al., 2007), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2007). The sorghum plant is more susceptible to drought stress at germination phase, near-germination phase, vegetative phase and post-flowering phase ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISSN 15608530, author dropping-particle , family Shazia Sakhi1, Shafiq ur Rehman2, Kazutoshi Okuno3, given Armaghan Shahzad4 and Mohammad Jamil5, non-dropping-particle , parse-names false, suffix , container-title International Journal of Agriculture and Biology, id ITEM-1, issue 2, issued date-parts 2014 , page 251-260, title Evaluation of Sorghum (Sorghum bicolor) core collection for drought Tolerance Pollen fertility and mean performance of yield traits and its components at reproductive stage, type article-journal, volume 16 , uris http//www.mendeley.com/documents/uuid99e67600-ad70-3609-a168-1b395a1d0d50 , mendeley formattedCitation (Shazia Sakhi1, Shafiq ur Rehman2, Kazutoshi Okuno3, 2014), manualFormatting (Sakhi et al., 2014), plainTextFormattedCitation (Shazia Sakhi1, Shafiq ur Rehman2, Kazutoshi Okuno3, 2014), previouslyFormattedCitation (Shazia Sakhi1, Shafiq ur Rehman2, Kazutoshi Okuno3, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sakhi et al., 2014). Thus, any screening technique should identify and select for tolerant cultivars at all phases of susceptibility to waterstress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-1, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007), manualFormatting (Reddy et al., 2007), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2007). 2.5.4.1.3 Introgressing the stay-green trait Most breeding programs employ pedigree and recurrent selection methods to develop staygreen candidate populations ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). The choice of method of introgression depends on the breeding objective ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family P.K. Subudhi. D.T. Rosenow. H.T Nguyen, given , non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid4e66a521-69c9-444b-91a0-85a900983ab6 , mendeley formattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), manualFormatting (Subudhi et al., 2000), plainTextFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), previouslyFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000). If the breeding objective is to introgress staygreen QTLs into high yielding drought susceptible local cultivar, backcrossing selection method can be used ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), manualFormatting (Rosenow et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rosenow et al., 2002) and if the aim is to develop staygreen population, recurrent and pedigree selection methods can be used ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family P.K. Subudhi. D.T. Rosenow. H.T Nguyen, given , non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid4e66a521-69c9-444b-91a0-85a900983ab6 , mendeley formattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), manualFormatting (Subudhi et al., 2000), plainTextFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), previouslyFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000). Introgression of staygreen trait is easily achieved because of high heritability of staygreen loci present in donor parents B35 and E-36-1 ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, given , non-dropping-particle , parse-names false, suffix , container-title Theoretical and Applied Genetics, id ITEM-1, issue 8, issued date-parts 2000 , page 1225-1232, title Identification of genomic regions associated with stay-green in sorghum by testing RILs in multiple environments., type article-journal, volume 100 , uris http//www.mendeley.com/documents/uuid0c5c6955-bcee-4252-9de9-650b436cd859 , id ITEM-2, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-2, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , id ITEM-3, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-3, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), manualFormatting (Subudhi et al., 2000 Reddy et al., 2007 Thomas and Ougham, 2014), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al., 2000 Reddy et al., 2007 Thomas and Ougham, 2014). 2.5.4.1.4 Selection criteria for staygreen Selection criteria for staygreen genotypes are best executed under controlled and drought-stress environments because of the polygenic nature of trait and high influence of genotype x environment interaction ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , id ITEM-2, itemData author dropping-particle , family Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., given Subhash Bharani and Vinayak Turaidar, non-dropping-particle , parse-names false, suffix , container-title Int. J. Pure App. Biosci., id ITEM-2, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid69473559-95d1-411c-87d6-aa2627b99dc0 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), manualFormatting (Beyene et al., 2017), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2017). Drought stress conditions offer the best chances for tolerant cultivars to be developed, identified and selected based on staygreen core features such as high yield and yield stability under drought stress condition ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Zhang, given Chun-qing, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2015 , title Genetic differentiation , heterotic performance and grain yield determinate traits of locally adapted sorghum genotypes in contrasting environments in Ethiopia Taye Tadesse Mindaye MSc in plant breeding A thesis submitted for the degree of Doctor of Philo, type article-journal , uris http//www.mendeley.com/documents/uuid19d35381-672d-4652-9e68-88e44493c4f9 , mendeley formattedCitation (Zhang, 2015), plainTextFormattedCitation (Zhang, 2015), previouslyFormattedCitation (Zhang, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Zhang, 2015). 2.6 Drought tolerance mechanisms of staygreen genotypes A number of mechanisms are involved namely morphological adaptations, physiological defense mechanism, biochemical defense mechanisms and hormonal defense mechanisms. 2.6.1 Morphological adaptations. Reduced canopy is an adaptation trait of staygreen genotypes that is linked to increased grain yield under post anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Staygreen genotypes reduce canopy to scale down water loss and maximize water use efficiency at flowering ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq et al., 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq et al., 2009). They do so through morphological modifications that reduced leaf area, tillering, leaf number per culm, plant height and leaf size ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalawai, given Ningaraj, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid59f72db8-f048-43ae-90ac-494ca55d53a7 , mendeley formattedCitation (Dalawai, 2017), plainTextFormattedCitation (Dalawai, 2017), previouslyFormattedCitation (Dalawai, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalawai, 2017). Leaf area can be reduced by reduced tillering ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014) while transpiration per unit leaf area can be reduced through reduced stomatal density, timing of stomatal opening and hydraulic factors ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , id ITEM-2, itemData DOI 10.1016/j.jplph.2015.10.009, ISSN 0176-1617, author dropping-particle , family Alessandra Fracassoa,u2217, Luisa Trindadeb, given Stefano Amaduccia, non-dropping-particle , parse-names false, suffix , container-title Journal of Plant Physiology, id ITEM-2, issued date-parts 2016 , page 1-14, publisher Elsevier GmbH., title Drought tolerance strategies highlighted by two Sorghum bicolor races in a dry-down experiment, type article-journal, volume 190 , uris http//www.mendeley.com/documents/uuide628efe0-9945-4d48-915c-49d262c2141b , mendeley formattedCitation (Alessandra Fracassoa,u2217, Luisa Trindadeb, 2016 Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014 Fracasso et al., 2016), plainTextFormattedCitation (Alessandra Fracassoa,u2217, Luisa Trindadeb, 2016 Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Alessandra Fracassoa,u2217, Luisa Trindadeb, 2016 Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Fracasso et al., 2016). By minimizing water use during the pre-anthesis phase, water is conserved for sustained grain filling during the grain development phase which leads to improved grain yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014 Beyene et al., 2015), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Beyene et al., 2015). 2.6.2 Physiological defense mechanism Selection for physiological characters is limited to secondary attributes for drought tolerance ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Knowledge of plant physiology has improved breeders understanding of the complex networks of drought tolerance traits, the genes conferring tolerance and how they can be exploited on conventional and genomic platforms to screen and select for cultivars with better adaptation to drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Robert E Schaffert, Paulo EP Albuquerque, Jason O Duarte, given Jou00e3o C Garcia, non-dropping-particle , parse-names false, suffix , dropping-particle , family Reinaldo L Gomide, Claudia T Guimaru00e3es, Paulo C Magalhu00e3es, given Jurandir V Magalhu00e3es and Valu00e9ria AV Queiroz, non-dropping-particle , parse-names false, suffix , container-title Drought phenotyping in crops from theory to practice, id ITEM-1, issued date-parts 2012 , number-of-pages 3-16, title Phenotyping sorghum for adaptation to drought, type book , uris http//www.mendeley.com/documents/uuid3deb8041-9b52-4361-9bf6-96132f93821b , mendeley formattedCitation (Robert E Schaffert, Paulo EP Albuquerque, Jason O Duarte Reinaldo L Gomide, Claudia T Guimaru00e3es, Paulo C Magalhu00e3es, 2012), manualFormatting (Schaffert et al., 2012 Harris et al., 2018), plainTextFormattedCitation (Robert E Schaffert, Paulo EP Albuquerque, Jason O Duarte Reinaldo L Gomide, Claudia T Guimaru00e3es, Paulo C Magalhu00e3es, 2012), previouslyFormattedCitation (Robert E Schaffert, Paulo EP Albuquerque, Jason O Duarte Reinaldo L Gomide, Claudia T Guimaru00e3es, Paulo C Magalhu00e3es, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Schaffert et al., 2012 Harris et al., 2018). Leaf rolling is a plant physiological defense mechanism against water stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Walulu, given Richard Sikuku, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1991 , title GENETIC CONTROL OF POST-FLOWERING DROUGHT TOLERANCE ( STAY GREEN ) IN SORGHUM by IN Submitted to the Graduate Faculty of Texas Tech University in Part i a 1 F u 1 f i 11 men t of the Requirements for the Degree of HASTER OF SCIENCE Approved, type article-journal , uris http//www.mendeley.com/documents/uuid9dc708ca-7067-406a-995a-2b7188df49f0 , mendeley formattedCitation (Walulu, 1991), plainTextFormattedCitation (Walulu, 1991), previouslyFormattedCitation (Walulu, 1991) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Walulu, 1991). Cereal crops use leaf rolling to signal yellowing and wilting ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A. D. Yoder,u2217 R. S. Beyer,u2020 andC.K.Jonesu2217, 1, given 2, non-dropping-particle , parse-names false, suffix , dropping-particle , family u2217Department, given , non-dropping-particle , parse-names false, suffix , container-title Poultry Science Association Inc., id ITEM-1, issue September, issued date-parts 2017 , page 177-185, title The effects of drought-affected grain and carbohydrase inclusion in starter diets on broiler chick performance, type article-journal, volume 24 , uris http//www.mendeley.com/documents/uuidd44edb01-37ff-4c0a-b78e-683549a49056 , mendeley formattedCitation (A. D. Yoder,u2217 R. S. Beyer,u2020 andC.K.Jonesu2217, 1 u2217Department, 2017), manualFormatting (Yoder et al., 2017), plainTextFormattedCitation (A. D. Yoder,u2217 R. S. Beyer,u2020 andC.K.Jonesu2217, 1 u2217Department, 2017), previouslyFormattedCitation (A. D. Yoder,u2217 R. S. Beyer,u2020 andC.K.Jonesu2217, 1 u2217Department, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Yoder et al., 2017). Leaf rolling occurs mostly at vegetative, pre anthesis, anthesis, and grain fill onset phase and tillering in water stress environments ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African journal of agricultural research, id ITEM-1, issue June, issued date-parts 2015 , page 1-15, title Physiological mechanisms of drought tolerance in sorghum , genetic basis and breeding methods A review Physiological mechanisms of drought tolerance in sorghum , genetic basis and breeding methods A review, type article-journal , uris http//www.mendeley.com/documents/uuidd06a4cc5-3780-4eb5-848c-215474d265d4 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015b), manualFormatting (Shimelis et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015b), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Shimelis et al., 2015). It contributes to drought tolerance by minimizing transpiration rate by altering leaf stomatal conductance and leaf area reduction ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, author dropping-particle , family Staggenborg, given Scott, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July 2015, issued date-parts 2010 , title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal , uris http//www.mendeley.com/documents/uuid0f41d9fc-2205-4045-a325-c02fa956d48e , mendeley formattedCitation (S. Staggenborg, 2010), manualFormatting (Staggenborg, 2010), plainTextFormattedCitation (S. Staggenborg, 2010), previouslyFormattedCitation (S. Staggenborg, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Staggenborg, 2010) as well as ameliorating heat intensity and incident solar radiation by lowering leaf temperature ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Leaf rolling is triggered by reduced leaf water potential although its severity varies among sorghum genotypes ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular BiologyrSpecial issue Cereal genomics, id ITEM-1, issue 5/6, issued date-parts 2002 , page 713-726, title Mapping QTLs associated with drought resistance in sorghum (Sorghum bicolor L. Moench), type article-journal, volume 48 , uris http//www.mendeley.com/documents/uuidd32b46f7-c950-4765-b4b5-eb0a3b53fedd , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b), manualFormatting (Sanchez et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sanchez et al., 2002). Severe leaf rolling is associated with diminished water potential ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015) and serves as an indicative of low leaf turgor attributed to poor osmotic adjustment ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1002/FES3.54, ISBN 2048-3694, ISSN 20483694, abstract Stress tolerance is a prerequisite for the success of biofuel production, which normally requires the use of marginal lands and nonfood biofuel feedstocks. Sorghum is known for its ability to withstand stress conditions, however, terminal stresses threaten its growth and development negatively impacting yield and sugar accumulation. It is crucial, therefore, that research aimed at developing sorghum resistance to stress factors should be pursued to expand the range of its growth to marginal and barren soils to meet the needs of a growing population, changing diets, and biofuel production. In this context, the leaf architectural trait of stay-green drought tolerance, in addition to salinity, cold, and aluminium toxicity and biotic stress tolerance and their genetic basis discussed in this review are expected to be available in future sweet sorghum ideotypes. Also highlighted is the key role of efficient management of farming systems, in particular the use of herbicides to control weeds, to ensure the sustainability of the sweet sorghum biomass productions., author dropping-particle , family Sylvester Elikana Anami 1, given 2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , Li-Min Zhang 1 , Yan Xia 1 , Yu-Miao Zhang 1, given Zhi-Quan Liu 1 Hai-Chun Jing, non-dropping-particle , parse-names false, suffix , container-title Food and Energy Security, id ITEM-1, issue 1, issued date-parts 2015 , page 3-24, title Sweet sorghum ideotypes Genetic improvement of stress tolerance, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuid392c6bf4-aff3-431e-a7c1-110d0ac9fe2c , mendeley formattedCitation (Sylvester Elikana Anami 1 , Li-Min Zhang 1 , Yan Xia 1 , Yu-Miao Zhang 1, 2015), manualFormatting (Anami et al., 2015), plainTextFormattedCitation (Sylvester Elikana Anami 1 , Li-Min Zhang 1 , Yan Xia 1 , Yu-Miao Zhang 1, 2015), previouslyFormattedCitation (Sylvester Elikana Anami 1 , Li-Min Zhang 1 , Yan Xia 1 , Yu-Miao Zhang 1, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Anami et al., 2015). Cultivars with favorable osmotic adjustment at low leaf water potential develop less leaf rolling ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African journal of agricultural research, id ITEM-1, issue June, issued date-parts 2015 , page 1-15, title Physiological mechanisms of drought tolerance in sorghum , genetic basis and breeding methods A review Physiological mechanisms of drought tolerance in sorghum , genetic basis and breeding methods A review, type article-journal , uris http//www.mendeley.com/documents/uuidd06a4cc5-3780-4eb5-848c-215474d265d4 , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a, 2015b), manualFormatting (Beyene et al., 2015 Shimelis et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a, 2015b), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a, 2015b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Shimelis et al., 2015) as exhibited by genotypes with functional staygreen trait ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, author dropping-particle , family Staggenborg, given Scott, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July 2015, issued date-parts 2010 , title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal , uris http//www.mendeley.com/documents/uuid0f41d9fc-2205-4045-a325-c02fa956d48e , mendeley formattedCitation (S. Staggenborg, 2010), manualFormatting (Staggenborg, 2010), plainTextFormattedCitation (S. Staggenborg, 2010), previouslyFormattedCitation (S. Staggenborg, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Staggenborg, 2010). If the plant initiates leaf rolling in the late phase of plant growth under post anthesis drought stress, it is indicative of continued plant growth and plant ability to recover after stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Waxy bloom is a life enhancing trait exhibited by manifold terrestrial plants for survival in abiotic and biotic stress prone agro-ecologies ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, ISSN 1543-7833, author dropping-particle , family Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, given , non-dropping-particle , parse-names false, suffix , container-title Cm, id ITEM-1, issue 1, issued date-parts 2010 , page 0, title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuid45d4794c-ee17-4dfc-8dc8-c9e4f0383fea , mendeley formattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), manualFormatting (Yared et al., 2010), plainTextFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), previouslyFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Yared et al., 2010). It plays an important role in maintenance of water potential ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, author dropping-particle , family Staggenborg, given Scott, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July 2015, issued date-parts 2010 , title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal , uris http//www.mendeley.com/documents/uuid0f41d9fc-2205-4045-a325-c02fa956d48e , mendeley formattedCitation (S. Staggenborg, 2010), manualFormatting (Staggenborg, 2010), plainTextFormattedCitation (S. Staggenborg, 2010), previouslyFormattedCitation (S. Staggenborg, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Staggenborg, 2010), leaf water retention ability ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, ISSN 1543-7833, author dropping-particle , family Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, given , non-dropping-particle , parse-names false, suffix , container-title Cm, id ITEM-1, issue 1, issued date-parts 2010 , page 0, title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuid45d4794c-ee17-4dfc-8dc8-c9e4f0383fea , mendeley formattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), manualFormatting (Assefa et al., 2010), plainTextFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), previouslyFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Assefa et al., 2010), drying avoidance ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq et al., 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq et al., 2009), excessive ultraviolent light reflectant ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq et al., 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq et al., 2009), insulation of plant against extreme solar radiation ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2134/advagricsystmodel1.c11, ISBN 978-0-89118-167-5, ISSN 2163-2790, abstract Drought and heat stress are among the two most important environmen- tal factors influencing crop growth, development, and yield processes. A comprehensive understanding of the impact of drought and heat stress will be critical in evaluating the impact of climate change and climate variabil- ity on crop production. Both drought and heat stress influence an array of processes including physiological, growth, developmental, yield, and qual- ity of crop. The objective of this review is to provide an overview of the influences of these two stresses on the above processes independently and in combination. Our review suggests a clear need of information on interactive effects of stresses particularly of drought and heat stress which mostly occur in combination. Both short- and long-term stresses can signifi- cantly influence growth and yield processes when stress occurs at sensitive stages. Crops are generally more sensitive to drought and/or heat stress during reproductive stages of development, which mainly influences seed numbers. Some of the important traits associated with drought- and/or heat-stress tolerance are indicated and discussed. The impacts of drought and heat stress are often different, and tolerance mechanisms may also be different. There is a wide range of crop modeling approaches (simple empirical models and more mechanistic models) that try to quantify the impact of stresses on growth, development, and yield and yield quality traits. These crop models should have the capability to quantify the impact of both short- and long-term stress events on growth, development, and yield processes. Modeling growth, development, sink-source relation, grain yield, and grain quality of crops can improve understanding of physi- ological and genetic nature of tolerance which can lead to increased grain yield and quality of crops. Improved models can enhance our capacity to predict crop performance in future climates and also to identify traits that can potentially be improved or exploited to obtain higher and more stable crop yields under stressed environments., author dropping-particle , family Staggenborg, given P. V. V. Prasad and S. A., non-dropping-particle , parse-names false, suffix , container-title Kanas Sate University, id ITEM-1, issued date-parts 2008 , page 301-356, title Impacts of Drought and/or Heat Stress on Physiological, Developmental, Growth, and Yield Processes of Crop Plants, type article-journal , uris http//www.mendeley.com/documents/uuid38cf3613-b8b8-4bb7-82c7-3f6670a9cf1c , mendeley formattedCitation (P. V. V. P. and S. A. Staggenborg, 2008), manualFormatting (Prasad et al., 2008), plainTextFormattedCitation (P. V. V. P. and S. A. Staggenborg, 2008), previouslyFormattedCitation (P. V. V. P. and S. A. Staggenborg, 2008) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Prasad et al., 2008) and enhanced water use efficiency in sorghum by regulating timely water loss ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , mendeley formattedCitation (Dalal, 2012), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012). Cuticular wax biosynthesis, translocation, deposition and compositions are influenced by environmental factors such as light, temperature, moisture and humidity in some species ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , id ITEM-2, itemData author dropping-particle , family MOHAMMED, given SUHEB, non-dropping-particle , parse-names false, suffix , dropping-particle , family Submitted. Dirk B. Hays. Amir Ibrahim.William L. Rooney.Russel W. Jessup.David D. Baltensperger, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family May, given , non-dropping-particle , parse-names false, suffix , id ITEM-2, issue May, issued date-parts 2014 , number-of-pages 2-85, title THE ROLE OF LEAF EPICUTICULAR WAX AN IMPROVED ADAPTATION, type report , uris http//www.mendeley.com/documents/uuid1bb78922-80a0-4fb0-aa19-451b1a371f41 , mendeley formattedCitation (Dalal, 2012 MOHAMMED, Submitted. Dirk B. Hays. Amir Ibrahim.William L. Rooney.Russel W. Jessup.David D. Baltensperger, May, 2014), manualFormatting (Dalal, 2012 Rooney et al., 2014), plainTextFormattedCitation (Dalal, 2012 MOHAMMED, Submitted. Dirk B. Hays. Amir Ibrahim.William L. Rooney.Russel W. Jessup.David D. Baltensperger, May, 2014), previouslyFormattedCitation (Dalal, 2012 MOHAMMED, Submitted. Dirk B. Hays. Amir Ibrahim.William L. Rooney.Russel W. Jessup.David D. Baltensperger, May, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012 Rooney et al., 2014). There are significant correlations between the wax contents and yield, water stress tolerance and water use efficiency in crops such as sorghum ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2135/cropsci2000.4041026x, author dropping-particle , family Borrell, given Andrew, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July, issued date-parts 2000 , title Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought I . Leaf Growth and Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought , type article-journal , uris http//www.mendeley.com/documents/uuid65dd2e28-15d2-480e-bcaa-58f578012f0b , id ITEM-2, itemData abstract Drought is the major environmental factor constraining crop production globally. Identifying and understanding the function of genes and gene networks that contribute to improved plant drought resistance under water-limited conditions is a fundamental component of sorghum breeding programs in Australia and the United States. In particular, genes located in four genomic regions (Stg1, Stg2, Stg3 and Stg4) controlling the functional basis of the B35 source of stay-green are being sought. Plants with the stay-green drought-resistance trait maintain green stems and upper leaves when water is limiting during grain filling. This paper discusses the multi-disciplinary approach to gene discovery implemented by Australian and U.S. scientists in pursuit of the key stay-green genes. In this project, map-based gene cloning is the primary approach to gene discovery. Multiple cycles of phenotyping and genotyping have enabled scientists to close-in on the genes of interest via fine-mapping, and will ultimately lead to the discovery of gene function. Candidate genes will be identified within each of the four genomic regions using an integrated genetic and physical map of sorghum, together with detailed physiological dissection of genotypes with different stay-green alleles. Proof of gene function will follow. Gene function in a range of environments will be assessed in silico using crop simulation modelling. Overall, this integrated approach to gene discovery will enable plant breeders to more efficiently custom-make sorghum varieties for specific water-limited environments. The discovery of stay-green genes in sorghum by Australian and U.S. scientists will lead to improved drought-resistance in sorghum, and potentially other major cereals., author dropping-particle , family Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, given Richard, non-dropping-particle , parse-names false, suffix , container-title 4th International Crop Science Congress, id ITEM-2, issue November 2015, issued date-parts 2004 , page 1-6, title Discovering Stay-Green Drought Tolerance Genes in Sorghum A Multidisciplinary Approach, type article-journal , uris http//www.mendeley.com/documents/uuidde2b9391-3c8a-4384-9f12-cb9a11c5fb75 , mendeley formattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004 A. Borrell, 2000), manualFormatting (Borrell, 2000 Borrell et al., 2004), plainTextFormattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004 A. Borrell, 2000), previouslyFormattedCitation (Andrew, Borrell. David, Robert, Jordan. Patricia, Klein. Robert, 2004 A. Borrell, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell, 2000 Borrell et al., 2004), Maize ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle LA, family FUENTE, given GERALD NEIL DE, non-dropping-particle , parse-names false, suffix , dropping-particle , family Subm. Seth C. Murray. Mike V. Kolomiets. Thomas S. Isakeit. David D. Baltensperger May, given , non-dropping-particle , parse-names false, suffix , container-title Texas A M University, id ITEM-1, issue May, issued date-parts 2012 , page 12-107, title BREEDING MAIZE FOR DROUGHT TOLERANCE DIVERSITY CHARACTERIZATION AND LINKAGE DISEQUILIBRIUM OF MAIZE PARALOGS ZMLOX4 AND ZMLOX5, type article-newspaper , uris http//www.mendeley.com/documents/uuid5e08b441-c27a-486d-b1b0-cd5d31851f7e , mendeley formattedCitation (FUENTE Subm. Seth C. Murray. Mike V. Kolomiets. Thomas S. Isakeit. David D. Baltensperger May, 2012), manualFormatting (Neil et al., 2012), plainTextFormattedCitation (FUENTE Subm. Seth C. Murray. Mike V. Kolomiets. Thomas S. Isakeit. David D. Baltensperger May, 2012), previouslyFormattedCitation (FUENTE Subm. Seth C. Murray. Mike V. Kolomiets. Thomas S. Isakeit. David D. Baltensperger May, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Neil et al., 2012) Barley ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Kiffu, Tarekega. Johns, Welbum. Dereje, given Assefa., non-dropping-particle , parse-names false, suffix , container-title Biodiversity Centre, id ITEM-1, issue 61, issued date-parts 2009 , title CBM MASTER THESES SERIES Agronomic evaluation of Ethiopian barley ( Hordeum populations under drought stress conditions in low- rainfall areas of Ethiopia Kiflu Tarekegn Abera, type article-journal , uris http//www.mendeley.com/documents/uuidc33a1a22-77ad-42e6-82a8-d7c585e1ed05 , mendeley formattedCitation (Kiffu, Tarekega. Johns, Welbum. Dereje, 2009), manualFormatting (Abera et al., 2009), plainTextFormattedCitation (Kiffu, Tarekega. Johns, Welbum. Dereje, 2009), previouslyFormattedCitation (Kiffu, Tarekega. Johns, Welbum. Dereje, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Abera et al., 2009) , Rice ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1002/9783527632930.ch36, ISBN 9783527328406, abstract Sorghum, the fifth most important cereal crop in the world, provides food, feed, fodder, fiber, and fuel. It is the second cereal crop and first C4 photosynthetic plant for which whole genome is sequenced. The importance of this crop will increase tremendously in future due to its better adaptability to abiotic stresses, which are expected to increase because of global climate change and diminishing fresh water supplies, coupled with increasing demand for food and bioenergy. The yield potential of sorghum is evident from the fact that production of sorghum has been maintained despite a steady decline in its area of cultivation over the past three decades. In fact, the true yield potential of sorghum has rarely been realized, as it is mainly grown in areas of low rainfall and resource-poor agronomic conditions. Owing to its ability to survive in water-limiting conditions, sorghum has majorly been studied for its drought resistance mechanism. The drought response in sorghum differs depending on the occurrence of stress during preflowering and postflowering. Postflowering response is associated with stay-green trait. Quantitative trait loci (QTL) for pre- and postflowering have been identified. However, the underlying genes that confer drought tolerance in sorghum have not been mapped. Moreover, other morphophysiological traits such as epicuticular wax content, osmotic adjustment, membrane stability, water use efficiency, or drought-related root traits that have been postulated to play a significant role in drought resistance in sorghum have been largely unexplored. Molecular genetic and physiological dissection of these traits will be of immense significance. Aluminum toxicity is a major problem in acidic soils. QTL and gene mapping approach led to the mapping of a Multidrug and Toxic Compound Extrusion (MATE) gene in sorghum. Later MATE family genes were identified as potential candidates that underlie aluminum tolerance QTL in maize. Since the rice, sorghum, and Brachypodium distachyon genome sequences are already available, and with impending maize genome sequence, there is an immense opportunity for comparative genetics and genomics to dissect abiotic stress tolerance mechanisms in cereals. This will accelerate the gene discovery among the cereal crops and will help improve other plant species as well. Thus, sorghum with its smaller genome, wide germplasm resource, well-studied genetics, C4 photosynthesis, and adaptability to harsh environments represu2026, author dropping-particle , family Monika, Dalal. Karthikeyan, Mauandi. Viswanathan, given Chinusamy., non-dropping-particle , parse-names false, suffix , container-title Improving Crop Resistance to Abiotic Stress, id ITEM-1, issue March, issued date-parts 2012 , page 923-950, title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal, volume 2 , uris http//www.mendeley.com/documents/uuidff499049-9c15-4680-81ad-a8daedb64bf7 , mendeley formattedCitation (Monika, Dalal. Karthikeyan, Mauandi. Viswanathan, 2012), manualFormatting (Dalal. et al., 2012), plainTextFormattedCitation (Monika, Dalal. Karthikeyan, Mauandi. Viswanathan, 2012), previouslyFormattedCitation (Monika, Dalal. Karthikeyan, Mauandi. Viswanathan, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal. et al., 2012) and wheat ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.3389/fpls.2016.01809, author dropping-particle , family u2020, given Jun Guo1, non-dropping-particle , parse-names false, suffix , dropping-particle , family u2020, given Wen Xu2, non-dropping-particle , parse-names false, suffix , dropping-particle , family u2020, given Xiaocong Yu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Shen2, given Hao, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given Haosheng Li, non-dropping-particle , parse-names false, suffix , dropping-particle , family Cheng1, given Dungong, non-dropping-particle , parse-names false, suffix , dropping-particle , family , Aifeng Liu1, given Jianjun Liu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Liu1, given Cheng, non-dropping-particle , parse-names false, suffix , dropping-particle , family Zhao2, given Shijie, non-dropping-particle , parse-names false, suffix , dropping-particle , family Song1, given and Jianmin, non-dropping-particle , parse-names false, suffix , container-title Frontiers in Plant Science, id ITEM-1, issue November, issued date-parts 2016 , page 1-10, title Cuticular Wax Accumulation Is Associated with Drought Tolerance in, type article-journal, volume 7 , uris http//www.mendeley.com/documents/uuid448d8bef-cd44-4500-b5c5-e25d617ab395 , mendeley formattedCitation (u2020 et al., 2016), manualFormatting (Guo et al., 2016), plainTextFormattedCitation (u2020 et al., 2016), previouslyFormattedCitation (u2020 et al., 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Guo et al., 2016). Plants with dense wax were found to have water stress tolerance and high yields relative to non-waxy crops ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.3389/fpls.2016.01809, author dropping-particle , family u2020, given Jun Guo1, non-dropping-particle , parse-names false, suffix , dropping-particle , family u2020, given Wen Xu2, non-dropping-particle , parse-names false, suffix , dropping-particle , family u2020, given Xiaocong Yu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Shen2, given Hao, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given Haosheng Li, non-dropping-particle , parse-names false, suffix , dropping-particle , family Cheng1, given Dungong, non-dropping-particle , parse-names false, suffix , dropping-particle , family , Aifeng Liu1, given Jianjun Liu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Liu1, given Cheng, non-dropping-particle , parse-names false, suffix , dropping-particle , family Zhao2, given Shijie, non-dropping-particle , parse-names false, suffix , dropping-particle , family Song1, given and Jianmin, non-dropping-particle , parse-names false, suffix , container-title Frontiers in Plant Science, id ITEM-1, issue November, issued date-parts 2016 , page 1-10, title Cuticular Wax Accumulation Is Associated with Drought Tolerance in, type article-journal, volume 7 , uris http//www.mendeley.com/documents/uuid448d8bef-cd44-4500-b5c5-e25d617ab395 , mendeley formattedCitation (u2020 et al., 2016), manualFormatting (Guo et al., 2016), plainTextFormattedCitation (u2020 et al., 2016), previouslyFormattedCitation (u2020 et al., 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Guo et al., 2016). Dense wax load is also positively correlated with harvest index ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family MOHAMMED, given SUHEB, non-dropping-particle , parse-names false, suffix , dropping-particle , family Submitted. Dirk B. Hays. Amir Ibrahim.William L. Rooney.Russel W. Jessup.David D. Baltensperger, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family May, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May, issued date-parts 2014 , number-of-pages 2-85, title THE ROLE OF LEAF EPICUTICULAR WAX AN IMPROVED ADAPTATION, type report , uris http//www.mendeley.com/documents/uuid1bb78922-80a0-4fb0-aa19-451b1a371f41 , mendeley formattedCitation (MOHAMMED et al., 2014), manualFormatting (Rooney et al., 2014), plainTextFormattedCitation (MOHAMMED et al., 2014), previouslyFormattedCitation (MOHAMMED et al., 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rooney et al., 2014). This suggests that genes that encode for biosynthesis of wax bloom can as well be utilized as valuable genetic resources for improving crop water stress tolerance and yield increment in drought prone agro-ecologies ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidf2050d8b-c3a2-4c98-92a1-72169c222f89 , mendeley formattedCitation (Dalal, 2012), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012). Osmotic adjustment enhances crop yield through delayed leaf rolling, leaf senescence and effective leaf area retention which keeps up the photosynthetic apparatus intact for continued biosynthesis of photosynthates ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2134/advagricsystmodel1.c11, ISBN 978-0-89118-167-5, ISSN 2163-2790, abstract Drought and heat stress are among the two most important environmen- tal factors influencing crop growth, development, and yield processes. A comprehensive understanding of the impact of drought and heat stress will be critical in evaluating the impact of climate change and climate variabil- ity on crop production. Both drought and heat stress influence an array of processes including physiological, growth, developmental, yield, and qual- ity of crop. The objective of this review is to provide an overview of the influences of these two stresses on the above processes independently and in combination. Our review suggests a clear need of information on interactive effects of stresses particularly of drought and heat stress which mostly occur in combination. Both short- and long-term stresses can signifi- cantly influence growth and yield processes when stress occurs at sensitive stages. Crops are generally more sensitive to drought and/or heat stress during reproductive stages of development, which mainly influences seed numbers. Some of the important traits associated with drought- and/or heat-stress tolerance are indicated and discussed. The impacts of drought and heat stress are often different, and tolerance mechanisms may also be different. There is a wide range of crop modeling approaches (simple empirical models and more mechanistic models) that try to quantify the impact of stresses on growth, development, and yield and yield quality traits. These crop models should have the capability to quantify the impact of both short- and long-term stress events on growth, development, and yield processes. Modeling growth, development, sink-source relation, grain yield, and grain quality of crops can improve understanding of physi- ological and genetic nature of tolerance which can lead to increased grain yield and quality of crops. Improved models can enhance our capacity to predict crop performance in future climates and also to identify traits that can potentially be improved or exploited to obtain higher and more stable crop yields under stressed environments., author dropping-particle , family Staggenborg, given P. V. V. Prasad and S. A., non-dropping-particle , parse-names false, suffix , container-title Kanas Sate University, id ITEM-1, issued date-parts 2008 , page 301-356, title Impacts of Drought and/or Heat Stress on Physiological, Developmental, Growth, and Yield Processes of Crop Plants, type article-journal , uris http//www.mendeley.com/documents/uuid38cf3613-b8b8-4bb7-82c7-3f6670a9cf1c , id ITEM-2, itemData author dropping-particle , family Morka., given Eyerusalem Arusi, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue June, issued date-parts 2015 , number-of-pages 5-70, title Physiological Indices for Drought Tolerance in Stay-green Sorghum (, type report , uris http//www.mendeley.com/documents/uuid2a1b438d-a114-431b-856b-6aac24e8ed2b , mendeley formattedCitation (Morka., 2015 P. V. V. P. and S. A. Staggenborg, 2008), manualFormatting (Prasad et al., 2008 Zhang et al., 2015), plainTextFormattedCitation (Morka., 2015 P. V. V. P. and S. A. Staggenborg, 2008), previouslyFormattedCitation (Morka., 2015 P. V. V. P. and S. A. Staggenborg, 2008) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Prasad et al., 2008 Zhang et al., 2015). Sustained photosynthesis and high assimilate content exhibited by genotypes with high osmotic adjustment confer improved yield compared to genotypes with low osmotic adjustment ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid2ea7fd05-ae86-4f12-a8ed-b0a4d0fb2c02 , id ITEM-2, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-2, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Amelework et al., 2015), plainTextFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2015). Genotypes with low osmotic adjustment do face competing demands for the remobilized assimilate to fill the grain and provide for energy required to keep up the osmotic adjustment processes running which leaves little or no assimilate for translocation up the plant for grain filling ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid2ea7fd05-ae86-4f12-a8ed-b0a4d0fb2c02 , id ITEM-3, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-3, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid3d00ee2a-6c7d-43c4-8f2e-0c866fc8d983 , mendeley formattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1, 2015 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Amelework et al., 2012 Beyene et al., 2015), plainTextFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1, 2015 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1, 2015 Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012 Beyene et al., 2015). The distinctive differences between genotypes with low and high osmotic adjustment is therefore expressed in the forms of grain size, grain number, grain weight, harvest index and biomass ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid2ea7fd05-ae86-4f12-a8ed-b0a4d0fb2c02 , mendeley formattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Amelework et al., 2012 Beyene et al., 2015), plainTextFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012 Beyene et al., 2015). All these differences vary with the genotype, stress intensity and duration ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJMR11.964, author dropping-particle , family Khayatnezhad, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family Gholamin, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 12, issued date-parts 2012 , page 2844-2848, title The effect of drought stress on leaf chlorophyll content and stress resistance in maize cultivars ( Zea mays ), type article-journal, volume 6 , uris http//www.mendeley.com/documents/uuid7c70688e-b994-4e24-8de0-5f453a2114d5 , mendeley formattedCitation (Khayatnezhad Gholamin, 2012), manualFormatting (Khayatnezhad and Gholamin, 2012), plainTextFormattedCitation (Khayatnezhad Gholamin, 2012), previouslyFormattedCitation (Khayatnezhad Gholamin, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Khayatnezhad and Gholamin, 2012). 2.6.3 Biochemical defense Mechanisms Biochemical defense mechanisms for drought tolerance involve accumulation of compatible solutes including proline, glycine-betaine and trehalose ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4161/psb.21949, author dropping-particle , family Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, given John Pichtel Aqil Ahmad, non-dropping-particle , parse-names false, suffix , container-title Plant Signalling and Behavior, id ITEM-1, issue August, issued date-parts 2017 , title Role of proline under changing environments Role of proline under changing environments A review, type article-journal, volume 2324 , uris http//www.mendeley.com/documents/uuid5bdeb828-da29-48b9-a98b-23f23a728e1e , mendeley formattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017), manualFormatting (Hayat et al., 2017), plainTextFormattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017), previouslyFormattedCitation (Shamsul Hayat, Qaiser Hayat, Mohammed Nasser Alyemeni, Arif Shafi Wani, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Hayat et al., 2017). These osmolytes maintain cells turgor and ameliorate the harmful effects of drought ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erv405, author dropping-particle , family Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, given Antoni R. Slabas1 and Marc R. Knight1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 22, issued date-parts 2015 , page 7061-7073, title Transcriptomic analysis comparing stay-green and senescent Sorghum bicolor lines identifies a role for proline biosynthesis in the stay-green trait, type article-journal, volume 66 , uris http//www.mendeley.com/documents/uuidad1a3d23-9955-4374-a05c-af92a8e1fa40 , mendeley formattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015), manualFormatting (Stephanie et al., 2015), plainTextFormattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015), previouslyFormattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Stephanie et al., 2015). Proline accumulation in sorghum genotypes promote cultivar recovery ability ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework et al., 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012). It provides for respiratory energy required by stress genotype to recover from water stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Proline determines critical water levels for which a plant can survive ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework et al., 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012). Its accumulation increases cell solute concentration which leads to increased water potential in the tissue through osmotic adjustments. The breeders use proline accumulation in sorghum as a good selection criterion for water stress tolerance ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Amelework et al.,2012 Beyene et al., 2015), plainTextFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Amelework, Beyene, 2012 Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al.,2012 Beyene et al., 2015). Plants with low-molecular weight soluble compounds function as protective mechanisms through osmotic adjustment, detoxication of reactive oxygen species, stabilization of cell membranes and structural integrity of enzymes and proteins ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq et al., 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq et al., 2009). In sorghum, glycine-betaine and sugar function as osmolytes that protect cells from dehydration, bleaching and rupture ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Glycine-betaine and sugars accumulation in the cell assist in maintenance of cellular water content and plant water status ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , mendeley formattedCitation (Amelework, Beyene, 2012), manualFormatting (Amelework et al., 2012), plainTextFormattedCitation (Amelework, Beyene, 2012), previouslyFormattedCitation (Amelework, Beyene, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Amelework et al., 2012). Plants use remobilized assimilate to enhances survival under post-anthesis drought stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15835/nsb.8.2.9790, author dropping-particle , family Ali AZARINASRABAD1, given 2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , Seyyed Mohsen MOUSAVINIK2, given Mohammad, non-dropping-particle , parse-names false, suffix , dropping-particle , family GALAVI2, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family , Seyyed Alireza BEHESHTI3, given Alireza SIROUSMEHR2, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue June, issued date-parts 2016 , page 204-210, title Evaluation of Water Stress on Yield , Its Components and Some Physiological Traits at Different Growth Stages in Grain Sorghum Genotypes, type article-journal, volume 8 , uris http//www.mendeley.com/documents/uuidbd3617c7-e5e6-4060-b24e-4d820a1326a0 , mendeley formattedCitation (Ali AZARINASRABAD1, , Seyyed Mohsen MOUSAVINIK2, GALAVI2, , Seyyed Alireza BEHESHTI3, 2016), manualFormatting (Azarinasrabad et al., 2016), plainTextFormattedCitation (Ali AZARINASRABAD1, , Seyyed Mohsen MOUSAVINIK2, GALAVI2, , Seyyed Alireza BEHESHTI3, 2016), previouslyFormattedCitation (Ali AZARINASRABAD1, , Seyyed Mohsen MOUSAVINIK2, GALAVI2, , Seyyed Alireza BEHESHTI3, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Azarinasrabad et al., 2016). Both photosynthetic assimilate and stem assimilates are used for growth of vegetative organs, grain filling and grain development ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, given and A.E. ENEJI, non-dropping-particle , parse-names false, suffix , container-title PHOTOSYNTHETICA, id ITEM-1, issue 4, issued date-parts 2004 , page 559-560, title Effect of drought on ear and flag leaf photosynthesis of two wheat cultivars differing in drought resistance, type article-journal, volume 42 , uris http//www.mendeley.com/documents/uuid480daf1e-0a24-42da-951c-690190bfc2c0 , mendeley formattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004), manualFormatting (Inoue et al., 2004), plainTextFormattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004), previouslyFormattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Inoue et al., 2004). Assimilate remobilization is stimulated if photosynthetic assimilate pathways are impaired by water stress, heat and diseases ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1111/pce.12800, author dropping-particle , family Blum, given Abraham, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July 2016, issued date-parts 2017 , title Osmotic adjustment is a prime drought stress adaptive engine in support of plant production . Osmotic adjustment and …. in support of plant production, type article-journal , uris http//www.mendeley.com/documents/uuid9bf3034d-275f-4dcd-9012-8a63a01cfadb , mendeley formattedCitation (Blum, 2017), plainTextFormattedCitation (Blum, 2017), previouslyFormattedCitation (Blum, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Blum, 2017). When post anthesis drought stress proceeds with irreversible damage to photosynthetic machinery, plants resort to utilizing assimilate remobilized from photosynthetic assimilate and pre-anthesis assimilate banked in the stem and leaves to fill their grains and power biochemical process. This specialized adaptation is specific to staygreen genotypes unlike senescence susceptible genotypes which depend only on remobilized pre-anthesis stem assimilates to fill their grains ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, given and A.E. ENEJI, non-dropping-particle , parse-names false, suffix , container-title PHOTOSYNTHETICA, id ITEM-1, issue 4, issued date-parts 2004 , page 559-560, title Effect of drought on ear and flag leaf photosynthesis of two wheat cultivars differing in drought resistance, type article-journal, volume 42 , uris http//www.mendeley.com/documents/uuid480daf1e-0a24-42da-951c-690190bfc2c0 , mendeley formattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004), manualFormatting (Inoue et al., 2004), plainTextFormattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004), previouslyFormattedCitation (T. INOUE, S. INANAGA, Y. SUGIMOTO, P. AN, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Inoue et al., 2004). Shortage of assimilate among drought sensitive genotypes leads to enhanced assimilate sink-source which creates a physiological burden to stem and leaves leading to wilting and drying off ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1094/CM-2010-1109-01-RV, ISSN 1543-7833, author dropping-particle , family Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, given , non-dropping-particle , parse-names false, suffix , container-title Cm, id ITEM-1, issue 1, issued date-parts 2010 , page 0, title Grain Sorghum Water Requirement and Responses to Drought Stress A Review, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuid45d4794c-ee17-4dfc-8dc8-c9e4f0383fea , mendeley formattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), manualFormatting (Assefa et al., 2010, plainTextFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010), previouslyFormattedCitation (Yared Assefa, Scott A. Staggenborg, and Vara P. V. Prasad, 2010) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Assefa et al., 2010 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Thomas Ougham, 2014b), manualFormatting Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014b), previouslyFormattedCitation (Thomas Ougham, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Thomas and Ougham, 2014). 2.6.4 Hormonal defense mechanisms Cytokinin is the most potent oppressor of senescence as it regulates it by ensuring late onset of senescence thus creating staygreen phenotype ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/978-90-481-2666-8_12, ISBN 9789048126651, ISSN 1774-0746, PMID 647, abstract Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteinu2026, author dropping-particle , family M. Farooq, A. Wahid, given N. Kobayashi D. Fujita S.M.A. Basra. Plant, non-dropping-particle , parse-names false, suffix , container-title Sustainable Agriculture, id ITEM-1, issued date-parts 2009 , page 153-188, title Plant drought stress Effects, mechanisms and management, type article-journal , uris http//www.mendeley.com/documents/uuid50a96bc6-2bfa-487e-95e0-17fd3bb4e067 , mendeley formattedCitation (M. Farooq, A. Wahid, 2009), manualFormatting (Farooq et al., 2009), plainTextFormattedCitation (M. Farooq, A. Wahid, 2009), previouslyFormattedCitation (M. Farooq, A. Wahid, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Farooq et al., 2009). Cytokinin mediated staygreen phenotype is a result of alteration in hormone metabolism and signalling in which cytokinin secretion is elevated and ethylene stimulation and secretion is inhibited ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4161/psb.24737, author dropping-particle , family Paul. J.Zwack and Aaron M. Rashotte, given , non-dropping-particle , parse-names false, suffix , container-title Plant Signaling and Behavior, id ITEM-1, issue May, issued date-parts 2013 , title Cytokinin inhibition of leaf senescence Cytokinin inhibition of leaf senescence, type article-journal , uris http//www.mendeley.com/documents/uuid456f78f3-4875-41e7-ba4b-39c857d736f8 , mendeley formattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013), manualFormatting (Rashotte et al., 2013), plainTextFormattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013), previouslyFormattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rashotte et al., 2013). 2.7 Mating design Mating design is defined as the procedure of producing the progenies ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). Mating design is alternatively defined as the process of making all possible crosses among the cluster of genotypes to produce subsequent filial generations ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family GRIFFING, given B., non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 1956 , title CONCEPT OF GENERAL AND SPECIFIC COMBINING ABILITY IN u2022 RELATION TO DIALLEL CROSSING SYSTEMS By B. GRIFFING, type article-journal , uris http//www.mendeley.com/documents/uuide1ddaf02-cae6-4a3d-afaa-db24e293b6dc , mendeley formattedCitation (GRIFFING, 1956), manualFormatting (Griffing, 1956 Yuewen et al., 2010), plainTextFormattedCitation (GRIFFING, 1956), previouslyFormattedCitation (GRIFFING, 1956) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Griffing, 1956 Yuewen et al., 2010). There are two known types of design in plant breeding namely the mating designs and the experimental designs ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). Breeders main interest in mating design is to find out if there is significant variation among the genotypes and if that variation is heritable and the gene action controlling their expressions ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s00122-002-1012-3, ISBN 0040-5752, ISSN 00405752, PMID 12582881, abstract The stay-green trait is a reported component of tolerance to terminal drought stress in sorghum. To map quantitative trait loci (QTLs) for stay-green, two sorghum recombinant inbred populations (RIPs) of 226 F(35) lines each were developed from crosses (1) IS9830 x E36-1 and (2) N13 x E36-1. The common parental line, E36-1 of Ethiopian origin, was the stay-green trait source. The genetic map of RIP 1 had a total length of 1,291 cM, with 128 markers (AFLPs, RFLPs, SSRs and RAPDs) distributed over ten linkage groups. The map of RIP 2 spanned 1,438 cM and contained 146 markers in 12 linkage groups. The two RIPs were evaluated during post-rainy seasons at Patancheru, India, in 1999/2000 (RIP 2) and 2000/2001 (RIP 1). The measures of stay-green mapped were the green leaf area percentages at 15, 30 and 45 days after flowering ( GL15, GL30 and GL45, respectively). Estimated repeatabilities for GL15, GL30 and GL45 amounted to 0.89, 0.81 and 0.78 in RIP 1, and 0.91, 0.88 and 0.85 in RIP 2, respectively. The number of QTLs for the three traits detected by composite interval mapping ranged from 5 to 8, explaining 31 to 42 of the genetic variance. In both RIPs, both parent lines contributed stay-green alleles. Across the three measures of the stay-green trait, three QTLs on linkage groups A, E and G were common to both RIPs, with the stay-green alleles originating from E36-1. These QTLs were therefore consistent across the tested genetic backgrounds and years. After QTL validation across sites and verification of the general benefit of the stay-green trait for grain yield performance and stability in the target areas, the corresponding chromosomal regions could be candidates for marker-assisted transfer of stay-green into elite materials., author dropping-particle , family Haussmann, given B. I.G., non-dropping-particle , parse-names false, suffix , dropping-particle , family Mahalakshmi, given V., non-dropping-particle , parse-names false, suffix , dropping-particle , family Reddy, given B. V.S., non-dropping-particle , parse-names false, suffix , dropping-particle , family Seetharama, given N., non-dropping-particle , parse-names false, suffix , dropping-particle , family Hash, given C. T., non-dropping-particle , parse-names false, suffix , dropping-particle , family Geiger, given H. H., non-dropping-particle , parse-names false, suffix , container-title Theoretical and Applied Genetics, id ITEM-1, issue 1, issued date-parts 2002 , page 133-142, title QTL mapping of stay-green in two sorghum recombinant inbred populations, type article-journal, volume 106 , uris http//www.mendeley.com/documents/uuid735c1ab1-4c17-44a8-9fe0-fa0f7b5ebd74 , mendeley formattedCitation (Haussmann et al., 2002), manualFormatting (Haussmann et al., 2002), plainTextFormattedCitation (Haussmann et al., 2002), previouslyFormattedCitation (Haussmann et al., 2002) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Haussmann et al., 2002). Mating designs are used for specific objectives such as to generate improved technologies, select for genetically valuable parents and devise a powerful selection procedure (Acquaah et al, 2012). The commonly used mating designs are North Carolina design I, II and III, Line x tester design and diallel I, II, III and IV (Acquaah et al., 2012). These designs aid to generate information on the genetic influence of a particular character by partitioning such genetic influence into either additive and or non-additive components ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al, 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al, 2012). The choice of these designs is affected by the objective of the study, breeder resources, time, space, cost of germplasm, pollination type, method of crossing, method of pollen dissemination (wind or insect), absence of male sterility, goal of the breeding program, the size of the breeding populations required and the availability of project infrastructure ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). A number of assumptions are employed in the use of the mating designs namely diploid behavior at meiosis, independence of genes distribution, no multiple alleles at the loci controlling the character, no reciprocal differences and no genotype x environment interactions ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family H. J. Gorz, F. A. Haskins, J. F. Pedersen, given and W. M. ROSS2 ABSTRACT, non-dropping-particle , parse-names false, suffix , container-title Plant Science Commons., id ITEM-1, issued date-parts 1987 , title Combining Ability Effects for Mineral Elements in Forage Sorghum Hybrids, type article-journal, volume 27 , uris http//www.mendeley.com/documents/uuid5a6079c0-2519-4932-a6bc-2ba41b5f480d , mendeley formattedCitation (H. J. Gorz, F. A. Haskins, J. F. Pedersen, 1987), manualFormatting (Gorz et al., 1987 , plainTextFormattedCitation (H. J. Gorz, F. A. Haskins, J. F. Pedersen, 1987), previouslyFormattedCitation (H. J. Gorz, F. A. Haskins, J. F. Pedersen, 1987) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Gorz et al., 1987 ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Shattuck, given , non-dropping-particle , parse-names false, suffix , dropping-particle , family Christie, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1993 , page 73-74, title Principles for Griffing s combining ability analysis, type article-journal , uris http//www.mendeley.com/documents/uuid030ba3f3-78d6-4496-9639-96aa92e2f3fb , mendeley formattedCitation (Shattuck Christie, 1993), manualFormatting Shattuck and Christie, 1993), plainTextFormattedCitation (Shattuck Christie, 1993), previouslyFormattedCitation (Shattuck Christie, 1993) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Shattuck and Christie, 1993). . Diallel is defined as a type of mating design use to study the genetic properties of particular inbred lines (Acquaah et al., 2012). Diallel is very informative in that it generates vital information about the combining ability of a particular line as well as estimating the genetic attributes of a population under study ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). The mostly used diallel mating designs are half diallel, full diallel and disconnected diallel. Diallel are distinguished on the basis of whether the parents or reciprocal effects are part in the model ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Isik, given Fikret, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2009 , page 1-34, title Analysis of Diallel Mating Designs, type article-journal , uris http//www.mendeley.com/documents/uuid041a73ae-a1fe-41ca-81d3-1a963720e479 , mendeley formattedCitation (Isik, 2009), plainTextFormattedCitation (Isik, 2009), previouslyFormattedCitation (Isik, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Isik, 2009). All diallel types do estimate the variation due to the crosses which is divided into sources due to general combining ability and specific combining ability ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Isik, given Fikret, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2009 , page 1-34, title Analysis of Diallel Mating Designs, type article-journal , uris http//www.mendeley.com/documents/uuid041a73ae-a1fe-41ca-81d3-1a963720e479 , mendeley formattedCitation (Isik, 2009), plainTextFormattedCitation (Isik, 2009), previouslyFormattedCitation (Isik, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Isik, 2009). A relatively large GCA and SCA variance ratio is an indicative of additive genetic effect and epistatic gene effect respectively ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Matheson, given Harry X. Wu A. C., non-dropping-particle , parse-names false, suffix , dropping-particle , family CSIRO, given , non-dropping-particle , parse-names false, suffix , container-title FOREST GENETICS, id ITEM-1, issued date-parts 2001 , page 205-212, title RECIPROCAL , MATERNAL AND NON-MATERNAL EFFECTS IN RADIATA PINE DIALLEL MATING EXPERIMENT ON FOUR AUSTRALIA SITES, type article-journal, volume 8(3) , uris http//www.mendeley.com/documents/uuid6873dd90-fff9-4e95-b9aa-d7cb22437448 , mendeley formattedCitation (Matheson CSIRO, 2001), manualFormatting (Harry et al., 2001), plainTextFormattedCitation (Matheson CSIRO, 2001), previouslyFormattedCitation (Matheson CSIRO, 2001) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Harry et al., 2001). The use of diallel enables the discrimination of parental lines by partitioning genetic influence into general combining ability and specific combining ability ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). 2.7.1 Combining ability Combining ability is defined as the ability of a parental line to perform well or worse in hybrid combination ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Laosuwan, given Paisan, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1975 , title Evaluation of lines from the sorghum conversion program for combining ability , heterosis , and genetic effects in single-cross and three-way hybrids, type article-journal , uris http//www.mendeley.com/documents/uuid0ab211c9-c5c0-4b3a-b1ad-74926e704698 , mendeley formattedCitation (Laosuwan, 1975), plainTextFormattedCitation (Laosuwan, 1975), previouslyFormattedCitation (Laosuwan, 1975) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Laosuwan, 1975). Combing ability acts as a precise tool for quantifying the nature of gene action underpinning quantitative trait ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Owolade, given O F, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 1, issued date-parts 2006 , page 98-104, title Diallel Analysis of Cassava Genotypes to Anthracnose Disease International Institute of Tropical Agriculture ( IITA ), Ibadan , Nigeria, type article-journal, volume 2 , uris http//www.mendeley.com/documents/uuid363316b5-d6d2-43c5-bed4-892212776e44 , mendeley formattedCitation (Owolade, 2006), plainTextFormattedCitation (Owolade, 2006), previouslyFormattedCitation (Owolade, 2006) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Owolade, 2006). The knowledge of combining ability is essential in understanding the inheritance of the characters, generation of superior lines as well as facilitating the selection of parental lines for hybrid ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-1, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Fasahat et al., 2016), plainTextFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Fasahat et al., 2016). The real measure of combining ability is progeny testing ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-1, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Fasahat et al., 2016), plainTextFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Fasahat et al., 2016). Combining ability is divided into general combining ability (GCA) and specific combining ability (SCA) ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al, 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al, 2012). General combining ability (GCA) is the mean performance of the genotypes in hybrid combination ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Gilchrest, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue August, issued date-parts 2017 , title Evaluation of Partially Converted Lines from the Sorghum Conversion Program to Determine Combining Ability and Heterosis for Early Testing by, type article-journal , uris http//www.mendeley.com/documents/uuid6292ffc1-c4f8-4077-8d6e-789c0e6dce94 , mendeley formattedCitation (Gilchrest, 2017), plainTextFormattedCitation (Gilchrest, 2017), previouslyFormattedCitation (Gilchrest, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Gilchrest, 2017) while specific combining ability (SCA) is the deviation of a cross from the mean performance of the parental genotypes ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Mutava, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2014 , page 219-225, title HETEROSIS AND COMBINING ABILITY IN A DIALLEL CROSS OF TURNIP RAPE GENOTYPES, type article-journal, volume 19 , uris http//www.mendeley.com/documents/uuid12bea3fb-31b2-490e-940a-ffaf03273813 , mendeley formattedCitation (Mutava, 2014), plainTextFormattedCitation (Mutava, 2014), previouslyFormattedCitation (Mutava, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Mutava, 2014). GCA is due to additive gene action whereas the SCA is due to non-additive gene action ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012). A low GCA estimate whether positive or negative indicates that the mean of a parent in a cross does not differ largely from the general mean of the crosses of the lines in combination. Conversely, a high GCA estimate indicates that the parental mean is superior or inferior to the general mean ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-1, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Fasahat et al., 2016), plainTextFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Fasahat et al., 2016). Superior genotypes are identified on the basis of performance of their progenies ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al, 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al, 2012). Both general and specific combining ability are important concepts for studying and comparing the performance of inbred lines ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Isik, given Fikret, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2009 , page 1-34, title Analysis of Diallel Mating Designs, type article-journal , uris http//www.mendeley.com/documents/uuid041a73ae-a1fe-41ca-81d3-1a963720e479 , mendeley formattedCitation (Isik, 2009), manualFormatting (Isik, 2009), plainTextFormattedCitation (Isik, 2009), previouslyFormattedCitation (Isik, 2009) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Isik, 2009). They generate genetic information useful for selecting for superior parent in hybrid combinations as well as delineating the type of gene action for various traits of economic value ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Mutava, given , non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2014 , page 219-225, title HETEROSIS AND COMBINING ABILITY IN A DIALLEL CROSS OF TURNIP RAPE GENOTYPES, type article-journal, volume 19 , uris http//www.mendeley.com/documents/uuid12bea3fb-31b2-490e-940a-ffaf03273813 , mendeley formattedCitation (Mutava, 2014), manualFormatting (Mutava, 2014 Chikuta et al., 2017), plainTextFormattedCitation (Mutava, 2014), previouslyFormattedCitation (Mutava, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Mutava, 2014 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5539/jas.v9n2p122, author dropping-particle , family Sally Chikuta1, 2, Thomas Odong1, given Fred Kabi1 Patrick Rubaihayo1 1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2017 , page 122-130, title Combining Ability and Heterosis of Selected Grain and Forage Dual Purpose Sorghum Genotypes, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuidef5ccb50-fbe9-4963-b276-c8e9f52e1504 , mendeley formattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), manualFormatting Chikuta et al., 2017), plainTextFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), previouslyFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Chikuta et al., 2017). The GCA and SCA concepts have also been used for genetic diversity evaluation, heterotic pattern classification and heterotic estimation ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , id ITEM-2, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-2, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (George, 2012 Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Acquaah et al., 2012 Fasahat et al., 2016), plainTextFormattedCitation (George, 2012 Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (George, 2012 Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012 Fasahat et al., 2016). Reciprocal crosses are involved in Griffing method I and Method III. These methods allow for partitioning of reciprocal effects into maternal effects and non-maternal effects ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Matheson, given Harry X. Wu A. C., non-dropping-particle , parse-names false, suffix , dropping-particle , family CSIRO, given , non-dropping-particle , parse-names false, suffix , container-title FOREST GENETICS, id ITEM-1, issued date-parts 2001 , page 205-212, title RECIPROCAL , MATERNAL AND NON-MATERNAL EFFECTS IN RADIATA PINE DIALLEL MATING EXPERIMENT ON FOUR AUSTRALIA SITES, type article-journal, volume 8(3) , uris http//www.mendeley.com/documents/uuid6873dd90-fff9-4e95-b9aa-d7cb22437448 , mendeley formattedCitation (Matheson CSIRO, 2001), manualFormatting (Harry et al., 2001), plainTextFormattedCitation (Matheson CSIRO, 2001), previouslyFormattedCitation (Matheson CSIRO, 2001) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Harry et al., 2001). The inclusion of reciprocal crosses is vital in that it positively influences the estimates of SCA effects (Mahgoub, 2011). Reciprocal crosses have been reported to have a major positive impact on determination of yield of hybrid ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-1, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Fasahat et al., 2016), plainTextFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Fasahat et al., 2016). CHAPTER THREE SCREENING SORGHUM GENOTYPES FOR DROUGHT TOLERANCE, EARLINESS AND HIGH YIELD 3.1 Introduction Sorghum is grown in all the states of South Sudan but more so in marginal areas with low rainfall and poor soil fertility occupying 859,662 hectares and producing 634,700 metric tonnes annually ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISBN 9789251097137, author dropping-particle , family FAO, given WFP, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May, issued date-parts 2017 , title FAO / WFP CROP AND FOOD SECURITY ASSESSMENT, type report , uris http//www.mendeley.com/documents/uuid0b0d9c40-c905-45f8-84a9-4f1b04b5de39 , mendeley formattedCitation (FAO, 2017b), manualFormatting (FAO, 2017), plainTextFormattedCitation (FAO, 2017b), previouslyFormattedCitation (FAO, 2017b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (FAO, 2017). The importance of sorghum lies in its roles as a cheap source of fibre, protein, carbohydrate, vitamins, fat, minerals (P, K, Fe Zn), phenolic acids, flavonoids and other bioactive compounds which act as antioxidants. Sorghum is also gluten free which makes it suitable as food for people with celiac disease ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family W.L.Rooney, given , non-dropping-particle , parse-names false, suffix , container-title Adavances in Agronomy, id ITEM-1, issued date-parts 2004 , page 1-75, title SORGHUM IMPROVEMENT- INTEGRATING TRDTIONAL AND NEW TECHNOLOGY TO PRODUCE IMPROVED GENOTYPES, type article-journal, volume 41 , uris http//www.mendeley.com/documents/uuidabe0e5bf-5543-4176-b4b6-aeb1e8bf9b81 , id ITEM-2, itemData author dropping-particle , family Amelework, Beyene, given Assefa, non-dropping-particle , parse-names false, suffix , id ITEM-2, issued date-parts 2012 , title Genetic Diversity Analysis of Lowland Sorghum Sorghum bicolor ( L .) Moench Landraces under Moisture Stress Conditions and Breeding for Drought Tolerance in North Eastern Ethiopia, type article-journal , uris http//www.mendeley.com/documents/uuid1dc565b3-ed50-41ac-b997-4764adff801e , id ITEM-3, itemData DOI 10.12983/ijsrk-2013-p154-162, ISBN 3070900100, ISSN 2322-4541, abstract Drought stress is a major constraint to sorghum production in Kenya, especially during flowering stage. This study aimed at developing drought tolerant sorghum varieties by transferring the stay green trait that confers drought tolerance in sorghum from a mapped and characterized donor source into an adapted farmer preferred variety. The drought tolerance donor source, E36-1 originally from Ethiopia was backcrossed into a Kenyan farmer-preferred variety, Ochuti until BC2F1 generation and the stay-green Quantitative Trait Loci (QTL) were transferred through Marker Assisted Breeding (MAB) strategy. Five polymorphic Simple Sequence Repeat (SSR) markers were used to select the 3 stay green QTL of E36-1 found in SBI-01, SBI-07 and SBI-10 linkage groups. In the F1 generation, two of these QTL, were transferred into three genotypes. In the BC1F1 generation, 32 genotypes had at least one QTL incorporated. From a population of 157 BC2F1 progenies, 45 genotypes had incorporated either one or two of the stay-green QTL. Despite a few number of genotypes obtained through the backcrosses, the results showed that stay-green QTL and consequently drought tolerance can be transferred successfully into farmer preferred sorghum varieties through MAB., author dropping-particle , family Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3, given Eunice W. Mutitu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1University, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Scientific Research in Knowledge, id ITEM-3, issue 6, issued date-parts 2013 , page 154-162, title Improving drought tolerance in Sorghum bicolor L. Moench Marker-assisted transfer of the stay-green quantitative trait loci (QTL) from a characterized donor source into a local farmer variety, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid9512ed63-81f0-41cf-8b72-01d141f0d051 , id ITEM-4, itemData DOI 10.4236/ajps.2015.69141, ISSN 2158-2742, abstract Sorghum (Sorghum bicolour (L.) Moench) grown under rain-fed conditions is usually affected by drought stress at different stages, resulting in reduced yield. The assessment of variation in mor-pho-physiological traits contributing towards drought tolerance at these stages is of vital impor-tance. This study was conducted using a split plot design with three replications to evaluate 25 sorghum accessions at post flowering stage under well watered and drought stress conditions at Hamelmalo Agricultural College. The data of 14 different morpho-physiological traits were sub-jected to analysis of variance, estimation of genetic variability and heritability and principal com-ponent analysis. We analyzed variance for seedling vigor, number of leaves, leaf area, stay-green, peduncle exsertion, panicle length and width, plant height, days to flowering and maturity, grain yield, biomass and harvest index under drought stress and irrigated conditions. The results showed that genotypic differences were significant at P 0.05 – 0.001. High magnitude of phe-notypic and genotypic coefficient of variations for plant height, harvest index and biomass as well as high heritability for days to flowering, panicle length, days to maturity and over all agronomic score were recorded. Principal component (PC) analysis showed that the first 4 PCs had Eigen value 1 explaining 74.6 of the total variation with grain yield, biomass, stay-green, leaf area, peduncle exsertion and days to flowering and maturity being the most important characters in PC1 and PC2. This research demonstrated high diversity for the characters studied. Moreover, the result showed that drought stress reduced the yield of some genotypes, though others were tole-rant to drought. Accessions EG 885, EG 469, EG 481, EG 849, Hamelmalo, EG 836 and EG 711 were Corresponding author. Tesfamichael et al. 1411 identified as superior for post-flowering drought tolerance and could be used by breeders in im-provement programs., author dropping-particle , family Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, given Aggrey Bernard Nyende2, non-dropping-particle , parse-names false, suffix , container-title American Journal of Plant Sciences, id ITEM-4, issue 6, issued date-parts 2015 , page 1410-1424, title Genetic Variation among Sorghum (Sorghum bicolor L. Moench) Landraces from Eritrea under Post-Flowering Drought Stress Conditions, type article-journal, volume 6 , uris http//www.mendeley.com/documents/uuid89f1c00f-d432-45c5-a43a-6755b0404895 , mendeley formattedCitation (Amelework, Beyene, 2012 Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015 W.L.Rooney, 2004), manualFormatting (Rooney et al., 2004 Amelework et al., 2012 Ngugi et al., 2013 Tesfamichael et al., 2015), plainTextFormattedCitation (Amelework, Beyene, 2012 Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015 W.L.Rooney, 2004), previouslyFormattedCitation (Amelework, Beyene, 2012 Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015 W.L.Rooney, 2004) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rooney et al., 2004 Amelework et al., 2012 Ngugi et al., 2013 Tesfamichael et al., 2015). The major constraints to sorghum on farm yield in South Sudan and Eastern Africa are prolonged water stress, frequent dry spell, heat intensity and lack of drought tolerance technologies to farmers who need them ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12983/ijsrk-2013-p154-162, ISBN 3070900100, ISSN 2322-4541, abstract Drought stress is a major constraint to sorghum production in Kenya, especially during flowering stage. This study aimed at developing drought tolerant sorghum varieties by transferring the stay green trait that confers drought tolerance in sorghum from a mapped and characterized donor source into an adapted farmer preferred variety. The drought tolerance donor source, E36-1 originally from Ethiopia was backcrossed into a Kenyan farmer-preferred variety, Ochuti until BC2F1 generation and the stay-green Quantitative Trait Loci (QTL) were transferred through Marker Assisted Breeding (MAB) strategy. Five polymorphic Simple Sequence Repeat (SSR) markers were used to select the 3 stay green QTL of E36-1 found in SBI-01, SBI-07 and SBI-10 linkage groups. In the F1 generation, two of these QTL, were transferred into three genotypes. In the BC1F1 generation, 32 genotypes had at least one QTL incorporated. From a population of 157 BC2F1 progenies, 45 genotypes had incorporated either one or two of the stay-green QTL. Despite a few number of genotypes obtained through the backcrosses, the results showed that stay-green QTL and consequently drought tolerance can be transferred successfully into farmer preferred sorghum varieties through MAB., author dropping-particle , family Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3, given Eunice W. Mutitu1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1University, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Scientific Research in Knowledge, id ITEM-1, issue 6, issued date-parts 2013 , page 154-162, title Improving drought tolerance in Sorghum bicolor L. Moench Marker-assisted transfer of the stay-green quantitative trait loci (QTL) from a characterized donor source into a local farmer variety, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid9512ed63-81f0-41cf-8b72-01d141f0d051 , mendeley formattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), manualFormatting (Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013), previouslyFormattedCitation (Kahiu Ngugi1, Wilson Kimani 1.2, Dan Kiambi2, 3 1University, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi et al., 2013). Both post anthesis and pre anthesis water stresses do completely destroy sorghum on farm yield. Post-anthesis water stress on one hand leads to lodging, reduced biomass, loss of chlorophyll, degradation of photosynthetic apparatus, reduced seed size ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Journal of Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-440, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor ( L .) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid2f0ae41d-8fa6-4c8f-89ff-8b6832f7aafa , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997), reduced seed weight ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5923/j.ijaf.20170701.01, author dropping-particle , family Abderhim A. Jabereldar1, Ahmed M. El Naim1,, Awad A. Abdalla1, given Yasin M. Dagash2, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1Department, given , non-dropping-particle , parse-names false, suffix , container-title International Journal of Agriculture and Forestry, id ITEM-1, issue 1, issued date-parts 2017 , page 1-6, title Effect of Water Stress on Yield and Water Use Efficiency of Sorghum ( Sorghum bicolor L . Moench ) in Semi-Arid Environment, type article-journal, volume 7 , uris http//www.mendeley.com/documents/uuid572bc36d-4f75-4c1c-ab3e-fd35def8d606 , mendeley formattedCitation (Abderhim A. Jabereldar1, Ahmed M. El Naim1,, Awad A. Abdalla1 1Department, 2017), manualFormatting (Jabereldar et al., 2017), plainTextFormattedCitation (Abderhim A. Jabereldar1, Ahmed M. El Naim1,, Awad A. Abdalla1 1Department, 2017), previouslyFormattedCitation (Abderhim A. Jabereldar1, Ahmed M. El Naim1,, Awad A. Abdalla1 1Department, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Jabereldar et al., 2017), reduced grain number, reduced 100-seed weight ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidf2050d8b-c3a2-4c98-92a1-72169c222f89 , mendeley formattedCitation (Dalal, 2012), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012) and enhances susceptibility to charcoal rot and premature sorghum leaf and stem senescence ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Journal of Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-440, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor ( L .) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid2f0ae41d-8fa6-4c8f-89ff-8b6832f7aafa , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997). Pre anthesis water stress on the other hand leads to late anthesis, floret abortion, reduced seed set, reduced panicle size, reduced plant height and premature death of plant ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid2ea7fd05-ae86-4f12-a8ed-b0a4d0fb2c02 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Sorghum is an important crop to South Sudan food security and farmer household income. It is cultivated by small-scale farmers for subsistence purpose and the surplus is marketed to earn income. The major sorghum grain attributes that determine grain and grain product marketing and consumption are grain quality, grain weight and grain product taste. Drought stress affects the dynamic of marketing because the desire and tendency to process grain sorghum by value addition groups depend on grain quality. The grain marketing by rural farmers is based on grain weight and grain product consumption by consumers is also determined by grain product quality taste. Drought stress affects these qualities by reducing grain weight, grain size and grain chemical components which leads to reduced protein and starch levels ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.3329/pa.v27i3.30806, author dropping-particle , family MA Khaton1, A Sagar2, JE Tajkia2, MS Islam3, MS Mahmud4, given AKMZ Hossain2, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1Department, given , non-dropping-particle , parse-names false, suffix , container-title Progressive Agriculture, id ITEM-1, issue December, issued date-parts 2016 , title Effect of moisture stress on morphological and yield attributes of four sorghum varieties, type article-journal , uris http//www.mendeley.com/documents/uuid5b75801f-69e7-4179-ab4d-35d4878f7d00 , mendeley formattedCitation (MA Khaton1, A Sagar2, JE Tajkia2, MS Islam3, MS Mahmud4 1Department, 2016), manualFormatting (Khaton et al., 2016), plainTextFormattedCitation (MA Khaton1, A Sagar2, JE Tajkia2, MS Islam3, MS Mahmud4 1Department, 2016), previouslyFormattedCitation (MA Khaton1, A Sagar2, JE Tajkia2, MS Islam3, MS Mahmud4 1Department, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Khaton et al., 2016). In order to alleviate water stress reduction of grain quality, nutrition quality and product quality taste, there is a need to collect, screen and identify germplasm that possess staygreen trait that can be improved and harnessed for adaptation to water stress in the drought prone agro-ecologies of Eastern Africa ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.12966/jra.08.02.2013, ISSN 2328-4951, abstract Drought stress is the major abiotic factor that limits cassava productivity in many agro-ecological regions of sub-saharan Africa. In this study, stay-green trait in two transgenic cassava genotypes (transformed with isopentenyl transferase (ipt) gene for improved drought tolerance) and six non-transgenic cassava genotypes were evaluated under green-house condi- tions. Leaf abscission (for leaf retention), elongation of the last internodes, photosynthetic rates, and stomatal conductance were determined in these cassava genotypes subjected to three levels of water stress treatments (0, 30, and 60 ) and a positive control or fully irrigated plants. Two non transgenic genotypes (98-0002 and 98-2226) and one transgenic line (529-48) that expressed relatively high level of stay green or leaf retention, also exhibited significantly higher photosynthetic rates, internode elongation and relatively low stomatal conductance compared to other genotypes. Non transgenic genotypes 91-02322 and TME-3 and transgenic line 529-28, expressed moderate levels of stay green and non transgenic genotype 95-0306 and wild type TMS 60444 (for the transgenic lines) were highly susceptible to the water stress treatments. The results reported here showed there was a positive correlation between leaf retention, photosynthetic rates, internode elongation and stomatal conductance., author dropping-particle , family Kahiu Ngugi 1,, Charles Orek 1,2, given Agnes Mwangu2019ombe, non-dropping-particle , parse-names false, suffix , container-title Journal of Renewable Agriculture, id ITEM-1, issue 5, issued date-parts 2013 , page 77-83, title Morphological and Physiological Measurement of the Stay-Green Trait in Transgenic and Non-Transgenic Cassava under Green-House Water Stress Conditions, type article-journal, volume 1 , uris http//www.mendeley.com/documents/uuid02bbe90c-3e3e-4c4e-bfad-0e673532ef51 , mendeley formattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013), manualFormatting (Ngugi et al., 2013), plainTextFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013), previouslyFormattedCitation (Kahiu Ngugi 1,, Charles Orek 1,2, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Ngugi et al., 2013). Introgressing functional Staygreen trait into South Sudan sorghum landraces will improve sorghum productivity and food security in water stress prone agro-ecologies. Sorghum genotypes with this trait do exhibit improved yield, yield components and yield stability in water stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, given , non-dropping-particle , parse-names false, suffix , container-title Theoretical and Applied Genetics, id ITEM-1, issue 8, issued date-parts 2000 , page 1225-1232, title Identification of genomic regions associated with stay-green in sorghum by testing RILs in multiple environments., type article-journal, volume 100 , uris http//www.mendeley.com/documents/uuid0c5c6955-bcee-4252-9de9-650b436cd859 , mendeley formattedCitation (Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), manualFormatting (Tao et al., 2000), plainTextFormattedCitation (Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), previouslyFormattedCitation (Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tao et al., 2000). The yield superiority of staygreen genotypes relative to water stress susceptible genotypes is associated with their higher level of cytokinin, stem sugars, leaf chlorophyll, biomass, leaf specific nitrogen, water potential and accumulated proline from flowering to physiological maturity ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4141/cjps2011-108, ISSN 0008-4220, author dropping-particle , family Ai-yu Wang1, Yan Li1, given and Chun-qing Zhang2, non-dropping-particle , parse-names false, suffix , container-title Canadian Journal of Plant Science, id ITEM-1, issue 2, issued date-parts 2012 , page 249-256, title QTL mapping for stay-green in maize ( Zea mays ), type article-journal, volume 92 , uris http//www.mendeley.com/documents/uuid44ffcb2e-7592-4856-9d6d-0a20a06f67d2 , id ITEM-2, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , mendeley formattedCitation (Ai-yu Wang1, Yan Li1, 2012 Dalal, 2012), manualFormatting ( Subudhi et al., 2000 Tao et al., 2000 Borrel et al., 2006 Dalal, 2012 Wang et al., 2012 Zwack and Aaron 2013 Borrell et al., 2014 Stephanie et al., 2015 Harris et al., 2018), plainTextFormattedCitation (Ai-yu Wang1, Yan Li1, 2012 Dalal, 2012), previouslyFormattedCitation (Ai-yu Wang1, Yan Li1, 2012 Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json ( Subudhi et al., 2000 Tao et al., 2000 Borrel et al., 2006 Dalal, 2012 Wang et al., 2012 Zwack and Aaron 2013 Borrell et al., 2014 Stephanie et al., 2015 Harris et al., 2018). Staygreen genotypes are also characterized by higher green leaf and stem duration (Borrell et al., 2014), higher efficacy of water conversion into biomass and grain yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , id ITEM-2, itemData DOI 10.1093/jxb/eru232, author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development , leaf anatomy , root growth , and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid649ca0af-e5b0-420e-bd9f-49917641ce2f , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b George, 2012), manualFormatting (Acquaah et al., 2012), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b George, 2012), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al., 2012) and improved balanced between water supply and water demand at flowering to grain fill phase ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/A1009673126345, ISBN 1380-3743, ISSN 13803743, abstract Drought is a serious agronomic problem and the single greatest factor contributing to crop yield loss in the world today. This problem may be alleviated by developing crops that are well adapted to dry-land environments. Sorghum (Sorghum bicolor (L.) Moench) is one of the most drought-tolerant grain crops and is an excellent crop model for evaluating mechanisms of drought tolerance. In this study, a set of 98 recombinant inbred (RI) sorghum lines was developed from a cross between two genotypes with contrasting drought reactions, TX7078 (pre-flowering-tolerant, post-flowering susceptible) and B35 (pre-flowering susceptible, post-flowering-tolerant). The RI population was characterized under drought and non-drought conditions for the inheritance of traits associated with post-flowering drought tolerance and for potentially related components of grain development. Quantitative trait loci (QTL) analysis identified 13 regions of the genome associated with one or more measures of post-flowering drought tolerance. Two QTL were identified with major effects on yield and staygreen under post-flowering drought. These loci were also associated with yield under fully irrigated conditions suggesting that these tolerance loci have pleiotropic effects on yield under non-drought conditions. Loci associated with rate and/or duration of grain development were also identified. QTL analysis indicated many loci that were associated with both rate and duration of grain development. High rate and short duration of grain development were generally associated with larger seed size, but only two of these loci were associated with differences in stability of performance under drought., author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-448, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid230720ce-0e29-43da-99cc-102a7b79dc5a , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997). The trait enhances resistance to lodging ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5923/j.plant.20170703.02, author dropping-particle , family Nasrein Mohamed Kamal1, 2, Yasir Serag Alnor Gorafi2, 3, Abdelbagi Mukhtar Ali Ghanim1, given 4, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1Biotechnology, given , non-dropping-particle , parse-names false, suffix , container-title Journal of Plant Research, id ITEM-1, issue 3, issued date-parts 2017 , page 65-74, title Performance of Sorghum Stay-green Introgression Lines Under Post-flowering Drought, type article-journal, volume 7 , uris http//www.mendeley.com/documents/uuidcf805f92-fae9-4a36-b8d6-f4975fdc5f97 , mendeley formattedCitation (Nasrein Mohamed Kamal1, 2, Yasir Serag Alnor Gorafi2, 3, Abdelbagi Mukhtar Ali Ghanim1 1Biotechnology, 2017), manualFormatting (Kamal et al., 2017), plainTextFormattedCitation (Nasrein Mohamed Kamal1, 2, Yasir Serag Alnor Gorafi2, 3, Abdelbagi Mukhtar Ali Ghanim1 1Biotechnology, 2017), previouslyFormattedCitation (Nasrein Mohamed Kamal1, 2, Yasir Serag Alnor Gorafi2, 3, Abdelbagi Mukhtar Ali Ghanim1 1Biotechnology, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Kamal et al., 2017), diseases ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014) and is associated with decreased canopy ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development , leaf anatomy , root growth , and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid649ca0af-e5b0-420e-bd9f-49917641ce2f , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014), reduced tillering ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid8f011332-1517-47ba-a047-6db413d8e6b4 , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Jordan et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Jordan et al., 2014), dwarf habit and insensitivity to photoperiod ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidd32610ec-6eab-44bc-97a7-ccdd209db283 , mendeley formattedCitation (Thomas Ougham, 2014a), manualFormatting (Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014a), previouslyFormattedCitation (Thomas Ougham, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Thomas and Ougham, 2014). Plants staygreen by employing host of defense mechanisms against water stress including phenological response mechanisms through early anthesis and early physiological maturity ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidf2050d8b-c3a2-4c98-92a1-72169c222f89 , mendeley formattedCitation (Dalal, 2012), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012). Physiological mechanisms is through high cuticular wax deposition, high stem reserves and photosynthetic efficiency ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid9685a000-c9cc-455b-849b-58657899804d , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Hormonal mechanism is achieved through sustained secretion of cytokinin and inhibition of ethylene ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1071/FP11101, ISBN 1445-4408, ISSN 14454408, abstract Drought resistance is being increasingly labelled as being a u2018complex traitu2019, especially with the recent expansion of research into its genomics. There is a danger that this labelmayturn into an axiom that is liable to damage education on the subject as well as research and the delivery of solutions to the farmer. This opinionated review examines whether there is grounds for such an axiom. Drought resistance is labelled as a u2018complex traitu2019 mainly when viewed by molecular biologists from the gene discovery platform. This platform is capable of expressing hundreds and thousands of drought-responsive genes, which are up- or down-regulated under dehydration stress according to growth stage, plant organ or even time of day. Sorting out the u2018grain out of the chaffu2019 in order to identify the function of the candidate genes towards drought resistance is difficult and, thus, the idea that drought resistance is complex is raised. However, when drought resistance is viewed from the physiological and agronomic whole-plant and crop platform, it appears much simpler its control, whether constitutive or adaptive, is rather obvious with respect to manipulation in breeding and crop management. The most important and common drought resistance traits function to maintain plant hydration under drought stress due to effective use of water (EUW). The state of our knowledge and the achievements in breeding for drought resistance do not support labelling drought resistance as a complex trait. Thegenomics road towards drought resistance is complex butwealreadyknowthat the destination is much simpler., author dropping-particle , family Blum, given Abraham, non-dropping-particle , parse-names false, suffix , container-title Functional Plant Biology, id ITEM-1, issue 10, issued date-parts 2011 , page 753-757, title Drought resistance is it really a complex trait, type article-journal, volume 38 , uris http//www.mendeley.com/documents/uuiddb34ce68-e6a1-4766-a98a-fb7f82791ba1 , id ITEM-2, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-2, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Blum, 2011 Thomas Ougham, 2014b), manualFormatting (Blum, 2011 Thomas and Ougham, 2014), plainTextFormattedCitation (Blum, 2011 Thomas Ougham, 2014b), previouslyFormattedCitation (Blum, 2011 Thomas Ougham, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Blum, 2011 Thomas and Ougham, 2014). Morphological adaptation mechanism are exhibited through dwarfism, reduced canopy and reduced tillering ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development , leaf anatomy , root growth , and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid649ca0af-e5b0-420e-bd9f-49917641ce2f , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Biochemical mechanisms operate through well balancing of osmolytes and production of anti oxidant defences ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Thomas Ougham, 2014b), manualFormatting (Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014b), previouslyFormattedCitation (Thomas Ougham, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Thomas and Ougham, 2014). There are emerging techniques breeders employ to generate staygreen genotypes in various plant species. Excessive production of chlorophyll through over expression of genes that encodes for chlorophyllide a oxygenase results into cosmetic type E staygreen ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidf2050d8b-c3a2-4c98-92a1-72169c222f89 , mendeley formattedCitation (Dalal, 2012), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Dalal, 2012). Hormonal staygreen is produced by stimulating secretion of cytokinin while ethylene is inhibited ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4161/psb.24737, author dropping-particle , family Paul. J.Zwack and Aaron M. Rashotte, given , non-dropping-particle , parse-names false, suffix , container-title Plant Signaling and Behavior, id ITEM-1, issue May, issued date-parts 2013 , title Cytokinin inhibition of leaf senescence Cytokinin inhibition of leaf senescence, type article-journal , uris http//www.mendeley.com/documents/uuid456f78f3-4875-41e7-ba4b-39c857d736f8 , mendeley formattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013), manualFormatting (Zwack and Aaron, 2013), plainTextFormattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013), previouslyFormattedCitation (Paul. J.Zwack and Aaron M. Rashotte, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Zwack and Aaron, 2013). Staygreen also results from minimized water use during vegetative phase allowing for water to be conserved for sustained longer grain fill duration ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid8f011332-1517-47ba-a047-6db413d8e6b4 , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Jordan et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Jordan et al., 2014). The aim of this study was to assess for water stress tolerance, earliness and yield in South Sudan sorghum germplasm and exotic lines to increase sorghum productivity for improved food security and poverty alleviation in water stress prunes agro-ecologies of South Sudan. 3.2 Materials and methods 3.2.1 Description of site of study The study was carried out for two consecutive seasons at ICRISAT-Nairobi field station at Kiboko in Makueni County. The experiment was conducted in the two years namely 2016 and 2017. Kiboko is located at 2 20 S latitudes and 37 45 E longitude. Kiboko lies in warm low-land of the semi-arid zone of eastern Kenya with an altitude of 900m above sea level. The area receives an annual rainfall of 604 per annum spread over two months of November and December with the maximum temperature of 29.40C and minimum temperature of 16.60C. 3.2.2 Germplasm Sorghum accessions comprising of 47 genotypes from South Sudan collection and 34 elite lines drawn ICRISAT were used (Table 3.1). The genotypes were chosen on the basis of farmer preference across Eastern Equatoria, Central Equatorial and Jonglei states of South Sudan. A number of check varieties were used in this study, namely Macia, Kiboko local 1 and Kiboko local2. Macia is a staygreen variety with B35 donor staygreen QTLs. It was released by ICRISAT in 2011 to semi arid agro-ecologies of East and Southern Africa. Kiboko local1 is a high yielding local variety with better adaptation to semi arid coastal agro-ecological zone while Kiboko local2 is an early maturing variety cultivated by farmers in semi-arid coastal areas of Kenya. Therefore, Macia was used as a check variety for staygreen trait Kiboko local 1 and 2 were used as check varieties for yield and earliness in this study. Table 3. 1. South Sudan sorghum germplasm and ICRISAT-Nairobi elite lines.EntryFarmerCultivarVillageCounty1James LakoLandi-whiteTereka centralTereka2James LakoLodokaTereka centralTereka3Emmanuel WuyaLodoka(white)Tereka centralTereka4Emmanuel WuyaJeriTereka centralTereka5Emmanuel WuyaMajoldiTereka centralTereka6Peter LadoMedengeDigalaJuba7Peter LadoLodokaDigalaJuba8Cecilia DokiJeriKuli papaJuba9Augustine TabanMerese(brown/red)Ganji payamJuba10Augustine TabanMerese(light brown)Ganji payamJuba11John OryamDeri(jeri)Rajaf payamJuba12Ikalik EnishaOlerereKudo payamTorit13IkalikOlodiongKudo payamTorit14IkalikOmuhathiLohiloTorit15IkalikOkabirKudo payamTorit16 Ayuen KuanyBerJongle Bor17 Ayuen ReechAkwar achotJonglei Bor18Joseph OtingDeriBur payamTorit19Joseph OtingDeriBur payamTorit20Idiongo ElijoMiteen(okoro)Bur payamTorit21Guido HayoroAmachihaBur payamTorit22Idiongo ElijoAlwalaBur payamTorit23John AmaharanyaAmachihaHilieuTorit24Atero DomnicAthatiHimodonge payamTorit25Miraya LabalangNatariCentral payamIkotos26Miraya LabalangNachotCentral payamIkotos27Miraya LabalangIbursarCentral payamIkotos28Miraya LabalangLolodokaCentral payamIkotos29Miraya LabalangBurjalureCentral payamIkotos30Mary KubalGwadaIkotosIkotos31Paul LochiLolodokaIkotosIkotos32Paul LochiOsman assaiIkotosIkotos33Lucia NaboyiNohonyek hohoroIkotosIkotos34Lokodo CiriloNolokidokCentral payamIkotos35Lokodo CiriloNolomutukCentral payamIkotos36Emilia MurangLobuhetiLomohidang n payamIkotos37Ajayo LadoKodu kineLirya payamJuba38Ajayo LadoLodoharieLirya payamJuba39Ajayo LadoLolikithaLirya payamJuba40Ille PelicheLowoi kudo payamOderiTorit41James LakoLoduduTereka centralTereka42James LakoLandi-redTereka centralTereka43 ICRISATGadam hamam Kiboko Makueni44 ICRISATHariray Kiboko Makueni45 ICRISATHugurtay Kiboko Makueni46 ICRISATICSR 161 Kiboko Makueni47 ICRISATICSV 111 IN Kiboko Makueni48 ICRISATIESV 23006 DL Kiboko Makueni49 ICRISATIESV 23010 DL Kiboko Makueni50 ICRISATIESV 91104 DL Kiboko Makueni51 ICRISATIESV 91111 DL Kiboko Makueni52 ICRISATIESV 91131 DL Kiboko Makueni53 ICRISATIESV 92028 DL Kiboko Makueni54 ICRISATIESV 92029 DL Kiboko Makueni55 ICRISATIESV 92043 DL Kiboko Makueni56 ICRISATIESV 92170 DL Kiboko Makueni57 ICRISATIESV 92172 DL Kiboko Makueni58 ICRISATIS 3679 Kiboko Makueni59 ICRISATKaguru Kiboko Makueni60 ICRISATBizany Kiboko Makueni61 ICRISATKiboko local 1 Kiboko Makueni62 ICRISATKiboko local 2 Kiboko Makueni63 ICRISATMacia Kiboko Makueni64 ICRISATMahube Kiboko Makueni65 ICRISATMugeta Kiboko Makueni66 ICRISATPP 290 Kiboko Makueni67 ICRISATWad ahmed Kiboko Makueni68 ICRISATZSV 3 Kiboko Makueni69 ICRISATCR 355 Kiboko Makueni70 ICRISATMbeere 81-3 Kiboko Makueni71 ICRISATTharaka 118 Kiboko Makueni72 ICRISATTharaka 6 Kiboko Makueni73 ICRISATIESB 2 Kiboko Makueni74 ICRISATWote collection 1 Kiboko Makueni75 ICRISATKhalid Kiboko Makueni76 ICRISATTabat Kiboko Makueni77 ICRISATAG 8 Kiboko Makueni78 AWIELMalual AwielAweil79 AWIELMakwach AwielAweil80 JONGLENuer bai Bor Bor81 ICRISATFarmer local Kiboko Makueni 3.2.3 Experimental design and layout The trials were set up in a 9 x 9 alpha lattice square design. Each trial was replicated three times with replicate spacing of 1.5m inter row spacing of 75cm and intra-row spacing of 20 cm. Drought stress was separated from well irrigated trial by a buffer zone of 7m. Overhead irrigation system was used to apply water to the trials every one week from sowing to when the seedlings were at the pencil length height. At second weeding to booting stage, irrigation was applied after every two weeks. Based on the data recorded from three rain gauges in each trial, drought stress trial received 90mm while well-watered trial received 120mm of irrigated water. To induce water stress in the drought stressed trial, irrigation was withheld at 50 flowering while well-watered trial continued to receive water till grain fill phase. On sowing, seeds were broadcasted into drills and later thinned to one plant per hill. The experiments were fertilized with Diammonium phosphate (DAP) – 18-46-0 (18 N, 46 P2O5, 0 K2O) at planting and top-dressed with calcium nitrate (CN) 15.5 N 19N.) at second weeding. 3.2.4 Data collection Data collected were grouped into agronomic, earliness, yield and drought tolerance characters. 3.2.4.1 Agronomic character Seedling vigor was visually scored after two weeks of germination on the scale of 1-7, where 1-3 stands for poor vigor, 4-5 for medium vigor and 6-7 for good vigor. Agronomic score was visually scored at the vegetative phase on the scale of 1-5, where 1- stands for very good, 2- stands for good , 3- stands for average, 4- stands for below average and 5- stands for poor management. 3.2.4.2 Drought tolerance characters. Waxy bloom (0-9) was visually scored at vegetative phase on the scale of (0-9), where 0- stands for no waxy bloom 1-3 stands for slightly present. 4-5- stands for medium bloom, 7-8 stands for mostly bloomy and 9- stands for completely bloomy. Leaf area (m2) was measured on the tagged the sampled plants by measuring leaf length and the width in centimeters at anthesis Chlorophyll content (SPAD-) was measured for five sampled plants on the fourth middle leaf after two weeks of drought stress onset for consecutive five weeks. Stem girth was measured in centimeters on the upper sheath of the fourth leaf at grain fill stage. Leaf rolling (1-5) was visually scored after two weeks of drought onset on the scale of 1-5 where 1- stands for evidence of leaf rolling, 2-3 stands for slightly rolled leaf, 4- stands for rolled leaf and 5- stands for cylindrical shape or completely rolled leaf. Lodging susceptibility (1-7) was visually scored at physiological maturity on the scale of 1-7, where 1-3 stands for low lodging, 4-5 stands for medium lodging and 6-7 stands for high lodging. Leaf senescence (1-9) was visually scored at physiological maturity on the scale of 1-9, where 0- stands for no senescence on the leaf and stalk. 1-2 stands for very slightly senescent leaf and stalk. 3- stands for slightly senescent leaf and stalk.4-5 stands intermediate leaf and stalk senescence, about half of leaves death and 6-7 stands for mostly senescent leaf and stalk.8-9 stands for completely senescent leaf and stalk. Leaf drying score (LDS) was visually scored at physiological maturity, leaf and stalk drying score was calculated by divided the number of dry leaves by total plants leaves number and multiplied by 100 as shown in (equation 5). DLS QUOTE . (5) 3.2.4.3 Earliness characters. Days to 50 germination was recorded at emergence phase when 50 of seedlings have emerged from the ground. Days to 50 flowering was obtained by counting days from emergence to when 50 of plants flowered. 3.2.4.4 Yield characters. Length of flag leaf (cm) was measured in centimeters at grain fill stage. The length of flag leaves of tagged sample plants per plot were measured in centimeters from the base of the leaf to the tip top of the leaf. Peduncle length (cm) was measured in centimeters from the base of the first node where he sheath of flag leaf attach to the base of the panicle at physiological maturity. Peduncle exertion (cm) was measured in centimeters from the sheath of the flag leaf to the bottom of the panicle. Panicle width (cm) was measured in centimeters from the widest middle position of the panicle at physiological maturity. Panicle length (cm) was measured in centimeters at physiological maturity from the base of the panicle to the upper tip top. Plant height (cm) was measured in centimeters at vegetative phase from the ground to the tip top of the panicle for five sampled plants per plot. Numbers of productive tillers were visually scored by counting per plant all reproductive tillers for five tagged plant samples at dough stage. Panicle weight (Kg) was measured in gram for harvested plant samples after physiological maturity. Threshability () was visually scored from values obtain after harvesting, threshing percentage is calculated mathematically by dividing grain of a plot sample by panicle weight of plot sample divided by 100.as showed in ( equation 6). Threshability QUOTE (6) Harvesting index () was obtained by dividing the grain weight by the biological yield and multiplied by 100 as shown in (equation 7). Harvest Index QUOTE . (7) 100-seedweight (Kg) was measured in gram by weighing100 seeds per plot. Grain yield (t ha-1) was recorded after threshing, heads of five randomly tagged plants were weighed and the yield was measured by weighing threshed grains of tagged grains samples in ton per hectares. 3.2.5 Data analysis 3.3.1.2 Mean performance of the sorghum genotypes at Kiboko The overall means for staygreen trait was 5.148 with mean range from 1.963 to 8. Based on mean range, all the genotypes were grouped into highly staygreen (1.963 to 3.9), intermediate staygreen (4.0 to 5.0) and non-staygreen (6 .0 to 7.852) (Table 3.3). The superior staygreen lines that outperformed the check variety were Olerere (1.963), Meresebrowred (2. 481), Lowoikudupayam (3.204), IESV92028DL (3.704), Gwada (3.704) and IESV23010DL (3.944). Over 50 sorghum genotypes expressed intermediate staygreen triat and 20 genotypes were highly susceptible to drought stress conditions (Table 3.3). As for leaf counts, the overall mean was 8.25.with mean range from 4.17 to 16.78. The highest total leaf counts were scored by genotypes Olerere (16.78), Amachiha1 (14.93) and Amachiha2 (14.33). The slightly leafy genotypes were Matual (4.7) Kaguru (4.34), Jeri1 (4.66), Majoldi (5.35), ZSV3 (5.4), Hugurtay (5.64), Hariray (5.86), Wotecollection1 (5.89), IESV23006DL (6.02), Nolomutuk (6.02) and Lolikitha (6.1) Table 3.3). For dry leaf score, the overall genotypic mean was 44.6 with mean range from 12.82 to 76.23). The lowest dry leaf score was recorded by top staygreen genotypes Olerere (12.02), Lowoikudopayam (19.43), Meresebrownred (20.09), and Macia (25.74). For leaf area, Large leaf area was recorded by staygreen landraces Meresebrownred (321m2), Olerere (295.4m2), Lowoikudupayam (285.5m2), Amachiha2 (279.7m2) and Amachiha1(274.3m2while Small leaf area was recorded by improved staygreen genotypes such as IESV91131DL(70.6m2), Mahube(74.9m2), IESV92029DL(82.2m2), IESV92172DL(88.7m2), PP290 (90.1m2), AG8 (91.7m2), Tabat (106.7m2), IESV91111DL (108.9m2), IESB2(110,9m2), Wadahmed(115.9m2), CR355 (117.1m2) Gadamhamam (119.1m2), IESV92028DL(119.5m2) and Macia(119.8m2). For waxy bloom, dense wax load was recorded by improved staygreen genotypes, Gwada, ICSR161, Mahube, AG8, IESV91131DL, IESV91111DL, IESV92028DL, IESV92172DL and Malual (Table 3.3). The overall mean for leaf rolling score was 4.907. Severe leaf rolling was recorded by genotype Omuhathi while rolled leaf was recorded by genotype, Nachot, Athati, Burialure, Derijeri, Jeri2, Lowoikudupayam, Olerere, Osmanassai and Medenge (Table 3.3). The genotypes that showed severe leaf rolling exhibit white leaf midrib colour, this suggests that leaf rolling occurs on pithy genotypes. The genotypes that showed resistance to lodging were predominantly improved staygreen lines namely IESV23010DL, ICSV111IN, IESV23006DL, IESV91131DL, IESV92170DL, Kaguru, Khalid, Kibokolocal, Mahube, Malual, Wadehamed, IESV92172DL, Kibokolocal2, CR355 and few landraces involving lines, Wotecollection1, Miteenokoro, Lobuheti, Lodoka2 and Lodudu (Table 3.3). 3.3.1.3 Means comparison for morphological characters under the two water regimes There was high variability among the genotypes for staygreen trait under water stress condition than well irrigated condition. The overall staygreen mean was 5.148 with mean range from 1.963 to7.882 compared to overall mean of 2.996 with mean range from 1.796 to 3.463 under well irrigated condition (Table 3.4) Total leaf counts was lower under drought stress condition with an overall mean of 8.23 leaves and mean range from 5.448 to16.041 leaves compared to well irrigated trials where total leaf counts was high recording an overall mean 9.227 and mean range from 4.17 to 16.78. Dry leaf score was higher under water stress condition with an overall mean 44.6 and mean range from 12.32 to 76.23compared to low DLS under well irrigated condition with an overall mean 14.25 and mean range from 6.53 to27.91. Leaf area was reduced under water stress condition recording an overall mean of 179.4cm2 and means range from 70.6 to 321cm2 compared to larger leaf area under well irrigated condition with an overall mean of 358.6cm2 and means range from 161.2 to 788.3cm2. Wax load was dense under waterstress condition recording an overall mean 5.344 and mean range from 2.259 to 8.37 mean compared to low load under well irrigated condition with an overall mean of 3.433 and mean range from 0.778 to 4.778 under well irrigated condition. Leaf rolling was high under drought stress condition with an overall mean of 2.864 and mean range from 1.524 to 4.907 compared to lower leaf rolling under well irrigated condition with an overall 1.161 and mean range from 0.741 to 2.463. Lodging was high under waterstress conditions with means range from 3.186 to 7.093 compared to reduced lodging under well irrigated condition with mean range from 0.556 to 4.074 (Table 3.4). 3.3.2 Assessment of phenology and yield components of South Sudan Sorghum germplasm 3.3.2.1 Assessment of growth components. The analysis of variance showed significant variations for all the growth related traits across the water regimes and the genotypes (Table 3.4). The interaction between the water regimes and genotypes showed significant differences for all traits except peduncle length and peduncle exertion (Table 3.4). Table 3.4. Means square of growth components of South Sudan and ICRISAT sorghum germplasm under well irrigated and drought stress conditionsSources of variationDFPHSGPELPEXPLPWIBMWater regimes177026.8211.51242668.921279.99547.91135.68.9575Genotypes8032414.22.2476610.54244.82441.317445.61.7456W X G801517.20.978347.92ns19.91ns100.3ns382.80.51Residual324556.80.420547.7727.58111.4170.20.3076Total485Key. DF degree of freedom, PH plant height. SG stem girth, PEL peduncle length, PEX peduncle exertion PWI panicle weight, AT aerial tillers and BM biomass 3.3.2.2 Mean performance of the sorghum genotypes with regard to the growth components Plant height recorded an overall mean of 179cm with mean range and 72.5cm to 318.8cm. The tallest genotypes were Meresebrownred (321cm) and Olerere (295.4cm) (Table 3.5). The shortest genotypes were Mahube, IESV91131DL, IESV92029DL, AG8, IESV92172DL, PP290, IESB2, Tabat and IESV91111DL (Table 3.5). Stem girth overall mean was 3.379cm with mean range from 1.6cm to 4.6cm. The highest stem girth was noted on genotypes Lowoikudopayam (4.681cm) and Amachiha2 (4.437cm). Peduncle length overall mean 49.3cm and mean range from 26.86cm to77.96cm. The largest peduncle length was recorded by genotype Lodoka2 (71.96cm), Natari (70.48cm), Osmanassai (68.25). Peduncle exertion recorded an overall mean of and 14.59cm and mean range from 2.91cm to 32.1cm. Longer peduncle exertion was noted on genotype, Lodoka1 (32.1cm), Nolokidok (29.02cm), Majoldi (27.9cm), Landiwhite (27.48cm), Natari (27.48cm) and Lodokawhite (26.16cm). The panicle width overall mean was 7.67cm and mean range from 3.77cm to 13.08cm. The widest panicle width was recorded for genotype Lodoka1 (13.08cm), Natari (12.43cm), Lolikitha (12.06cm), Lodoka2 (11.28cm), Lodokawhite (10.93cm), Kibokolocal1 (10.23cm). Panicle length recorded an overall mean of 24.15cm with mean range from 7.65cm to 102.72cm. The longest panicle length was recorded by genotypes Lodoka1 (102.72cm), Jeri1 (42.26cm), Amachiha1 (38.72cm), Nohonyekhoro (37.34cm), Lodoka2 (34.17cm). Biomass recorded an overall mean of 1.115kgwith mean range from 0.0156kg to 2.374kg. Higher biomass was given by genotype, Mahube (2.374cm), IESV91131DL (2.333kg), Gadamhamam (2.163kg), Amachiha1 (1.976kg), Mereselightbrown (1.963kg), Lodoka2 (1.939kkg), Jeri2 (1.896cm), ICSR161 (1.863kg), Nachot (1.824kg), Olerere (1.796kg), Burialure (1.722kg) and Lodokawhite (1.7kg). 3.3.2.3 Mean Comparisons for growth Components. Mean comparison (Table 3.6) showed significant mean differences for all growth characters studied across both treatments. Sorghum genotypes under drought stress condition recorded reduced overall means for growth characters compared to genotypes under well irrigated condition. Stem girth recorded mean reduction from 4.7 to 3.4. Despite drought stress reduction, genotype Mugeta gave the highest stem girth under drought stress conditions than under well irrigated condition. For plant height, mean reduction was from 204.2cm to 179cm. Accessions that gave taller heights under drought stress condition than to under control were CR355, ICSR161, IESV23006DL, IESV923010DL, IESV92043DL, Jeri1, Kodukine, Malual, Okabir, Tharaka11 and Wotecollection1. Peduncle length recorded reduction from 53.99cm to 49.3cm. Longer peduncle length under water stress than control was given by accessions Ber, IESV92043DL, IESV92172DL, Kaguru, Kibokolocal1, Kibokolocal2, Kodukine, Lodoka2, Lolodoka2, Macia, Makuach, Matual, Meresebrownred and Mereselightbrown. Peduncle exertion recorded mean reduction from 17.94cm to 49.3cm but drought reduction effect was not observed on genotypes Alawala, Gadamhamam, Hariray, IESV91131DL, IESV92172DL, Lodoka1, Lolodoka1, Makuach, Matual, Meresebrownred and Tharaka6. Panicle length recorded mean reduction from 26.27cm to 24.15cm. Longest panicle length under waterstress than control were given by accessions, Gadamahamam, IESB2, IESV92029DL, Kaguru, Kibokolocal1, Kibokolocal2, Kodukine, Lodoka1, Lodoka2, Lolikitha, Macia, Majoldi, Malual, Nolomutuk, Tabat, Tharaka6, and Wadahamed. Panicle width recorded mean reduction from 9.27cm to 7.67cm. The genotypes that showed increased panicle width under drought stress than under well irrigated conditions were CR355, Farmerlocal1, Gadamahamam, Kaguru, Kibokolocal1, Landiwhite, Lodoka1, Lodoka2, Lodokawhite, Lolikitha, Matua, Mbeere813 and Tharaka11. Biomass was reduced from 0.8464kg to1.7697kg. The genotypes that recorded higher biomass under waterstress compared to under well irrigated conditions were Alwala, Amachiha1, Amachiha2, Athati, Bizany, Deri1, Famrerlocal, Jeri2, Khalid, Kibokolocal1, Landiwhite, Lobuheti, Lodoharie, Lodudu, Nolokidok, Olerere, and Olodiong (Table 3.5). Analysis of variance showed significant differences for all the traits across the water regimes and genotypes at p0.05. The interaction between water regiments by genotypes showed significant differences for all the traits except days of flowering, basal tillers, 100 seed weight and threshability (Table 3.6). Table 3.6 Means square of phenology and yield components of South Sudan and ICRISAT sorghum germplasm,Sources of variationDFDOF LFLBTPAWTGWTHSMTHHIWater regimes13022.523295.770.0053ns17445.68438.919.7412317.9ns89.449Genotypes802530.03194.981.8391135.6492.81.7411344.820.328W X G8077.79ns90.26 0.3306ns382.8218.10.3867ns284ns16.399Residual32484.1758.60.2279170.2123.30.3055202.17.971Total485 DF degree of freedom, DOF days to flowering, LFL length of flag leaf, BT basal tillers, PAWT panicle weight, GWT grain weight, HSM 100- seed weight, TH threshability and HI harvest index. 3.3.3.2 Mean performance of the sorghum genotypes with regard to plant phenology and yield components Based on means range, the germplasm were grouped into early lines (56 to 60 days), medium lines (70- 88 days) and late lines (90- 135.33 days). The superior genotypes for earliness than the check variety were Wotecollection1 (56.94days), IESV23010DL (58.06days, ZSV3 (60.09days), Bizany (61.17days) and Tabat (61.17days). Over 28 lines were medium. Themost late lines were Amachiha2 (135.83days), Meresebrownred (134.41cm), Olerere (131.96cm) (Table 3.7). Largest length of flag leaf was recorded by genotype Lodoka1 (46.07cm), Lodoharie (46.01cm), Lolikitha (44.67cm), Natari (44.01cm), Ibursar (42.73cm), IESV92043DL (42.37cm), Nachot (41.93cm), IESV23010DL (41.51cm), Lodudu (41.32cm), IESV92172DL (40.93cm), Burialure (40.66cm), Gwada (40.61cm) and Miteenokoro (40.3cm). The highest panicle weight was recorded by genotype Lobuheti (75.92g), Kibokolocal1 (73.84g), IESV92170DL (71.58g), Lodoka2 (71.11g), IESV92043DL (69.77g), Lodoka1 (69.38g), Mereselightbrown (68.95g), IESV91131DL (68.98g), Nohonyekhoro (68.92g), IESV92028DL (66.47g), Meresebrownred (66.08g), IESV92029dl (66.89G), iesv92172DL (66.5g). The genotypes Lobuheti (50.65g), IESV91131DL (46.52g), Lodoka1 (47.08g) and IESV92172DL (46.69g) were superior for yield than the check variety. The highest 100-seed weight was recorded by genotypes Hugurtay (3.767g), ZSV3 (3.724g), Malual (3.602g), Akuorachot (3.365g), CR355 (2.93g), IESV92170DL (2. 909g), Omuhathi (2.88g), AG8 (2.85), IESV23010DL (2.754g), IESV23006DL (2.754g), (Mbeere813(2.685g), Nohonyekhohoro (2.646g), , ICSR161 (2.619g) , Kodukine (2.593g), Majoldi (2.587g), Wotecollection1 (2.544g). Threshability was relatively high for genotypes IESV23006DL (87.62), Majoldi (82.08g), IESV23010DL (81.02g), Mahube (80.74g), Farmerlocal (80.42), Ber (79.68g), IESB2,(78.31g), Akuorachot,(78.1), CR355 (75.85), , Makuach (75.79g) and IESV91131DL (73.94). Low threshability was given by genotypes Amachiha2 (37.89), Okabir (38.99), Lolodoka1 (43.75g), Nachot (47.97), Natari (50.46), Lodoka2 (52.66) and AG8 (53.54). The genotypes that showed increased harvest index under drought stress were Landiwhite (10.81), Lodudu (10.01), Lodoka1 (9.9), Jeri (7.83), IESV111IN (7.33), Medenge (7.27), Kibokolocal1 (7.14), IESV92172DL (6.86), Landired (6.67), Amachiha2 (6.48), Tharaka11 (6.47), Farmerlocal (6.44)and Nolokidok (6.37) (Table 3.7) Table 3.7 Effect of water stress on phenology and yield characters of South Sudan and ICRISAT sorghum germplasmGenotypes DFLFLBTBMPAWTGWTHSMTH ()HI ()AG863.7431.550.3851.05641.6722.332.8553.543.05Akuorachot61.5230.861.1221.43752.4141.913.36578.22.99Alwala109.9633.712.1671.04341.2325.962.1559.375.08Amachiha1120.4836.320.9931.97663.1937.231.561.952.91Amachiha2135.8340.040.330.54863.0727.941.8537.896.48Athati113.9631.641.5070.39641.8124.252.38762.515.86Ber67.6322.460.40.843.1134.332.4779.684.68Bizany61.1734.20.0670.30736.5721.322.20260.334.76Burialure102.4640.661.3111.72237.6520.591.59353.971.3CR35564.9828.070.1561.61135.3325.192.9375.853.69Deri1115.9332.561.8330.72864.2739.282.02460.397.03Deri2105.8132.031.2561.54861.2135.441.42464.152.14Derijeri118.4327.951.3411.63946.231.11.94661.992.54Farmerlocal69.4131.10.80.5555.443.981.92880.426.44Gadamhamam63.532.460.6072.16337.625.432.26365.82.11Gwada122.740.611.1561.54664.5137.431.67653.965.14Hariray62.2428.960.1480.77241.323.162.33756.593.87Hugurtay80.2225.480.6520.47829.0118.843.76761.334.6Ibursar104.1942.731.6190.92833.4921.392.1562.492.49ICSR16166.5239.85-0.0151.86358.8539.532.61967.732.77ICSV111IN58.3135.730.0520.74357.9341.52.51171.347.33IESB266.0237.75-0.0960.70441.4132.391.39678.313.25IESV23006DL62.4435.430.1781.40743.5536.592.75487.625.09IESV23010DL58.0641.510.3260.60748.9839.222.75481.025.04IESV91104DL67.7231.830.2440.81154.238.482.50973.536.12IESV91111DL66.3134.460.031.18345.8333.672.27873.942.98IESV91131DL70.3134.280.0562.33368.9548.521.84869.943.13IESV92028DL68.1139.28-0.0261.29368.4744.222.09165.093.84IESV92029DL75.3736.36-0.0111.34366.8944.11.73365.723.2IESV92043DL71.7642.37-0.0041.30669.7735.922.22851.984.72IESV92170DL73.6338.670.0671.3371.5842.582.90961.233.71IESV92172DL70.9440.930.0150.93166.546.692.20667.346.86Jeri176.3934.251.9261.10450.9433.921.89668.327.83Jeri2119.3326.950.8891.89649.3931.672.09365.383.2Kaguru62.6724.211.7811.0534.0625.021.99867.992.62Khalid65.234.76-0.0741.10450.7834.112.31966.116.05Kibokolocal170.0438.380.1480.56173.8446.581.99360.57.14Kibokolocal261.4136.690.3811.06144.128.872.03365.22.67Kodukine61.9636.97-0.0071.47645.732.112.59371.882.97Landired67.4137.390.6810.56558.9740.361.99468.566.67Landiwhite66.2831.561.0960.15657.7637.871.69666.3810.81Lobuheti69.2233.750.2220.86575.9250.652.21564.295.52Lodoharie61.4846.010.7070.93560.7937.982.35605.57Lodoka1112.0646.070.9560.72669.3847.082.06168.679.9Lodoka286.8339.470.8481.93971.1136.881.68752.663.39Lodokawhite97.2237.170.5221.754.1130.382.00453.722.04Lodudu71.0941.321.2780.53957.6840.551.82670.3210.01Lolikitha6644.670.6370.84659.1739.542.26963.36.04Lolodoka190.3935.071.2480.82245.6725.732.00943.753.57Lolodoka288.0636.652.1440.96552.5138.632.176.735.99Lowoikudopayam113.7638.461.431.60928.6315.972.14863.922.42Macia70.0732.43-0.0151.43366.2644.21.73566.73.25Mahube69.2838.790.0742.37436.6329.411.78580.741.76Majoldi65.8726.631.6191.0350.8939.682.58782.085.49Makuach82.7628.480.6110.45742.8632.192.41775.794.29Malual71.5732.190.2930.74143.9835.363.60280.136.25Matual82.4825.131.6930.45431.8732.452.19362.675.17Mbeere81364.4337.290.2191.33942.6226.762.68566.412.08Medenge113.7836.131.1810.3046138.661.73163.067.27Meresebrownred134.4118.20.1961.3868.0844.351.74164.934.63Mereselightbrown84.6532.70.4371.96368.9839.931.66356.582.63Miteenokoro65.6540.30.670.90752.7935.371.74366.685.83Mugeta79.231.41.2930.84435.9223.041.85664.483.31Nachot91.8341.931.2591.82431.6119.581.99147.971.71Natari94.9444.011.5331.41351.9526.561.65250.452.18Nohonyekhohoro77.9838.810.9111.568.9242.192.64659.184.67Nolokidok86.2235.971.2670.20659.3336.591.99860.446.37Nolomutuk74.3290.831.27637.8322.31.6254.572.72Nuerbai63.8526.140.9810.4731.6818.572.163.554.72Okabir77.530.91.0631.35444.0817.321.79338.992.54Olerere131.9820.140.0851.79645.2227.481.62457.81.32Olodiong126.7214.870.470.87439.9322.941.98165.092.98Omuhathi108.3126.292.2811.59326.4419.092.8866.870.98OsmanAssai117.3336.21.2440.68127.2118.382.48958.672.74PP29066.1935.580.1781.55458.1636.912.06358.64.72Tabat61.1731.820.7411.53743.9330.962.09167.016.12Tharaka11864.5719.980.7040.63145.7133.712.33375.56.47Tharaka665.8530.91.5930.55756.8640.422.3768.036.35Wadahmed61.5732.490.8931.26940.9525.791.966.273.61Wotecollection156.9428.010.9930.51526.3416.622.54463.833.95ZSV360.0923.720.4261.00438.8725.763.72470.112.91Mean81.4633.80.7561.11550.2432.82.19164.774.43CV12.723.15968.927.227.623.620.165.5L.S.D (P 0.05)23.91618.0290.7781.769731.53520.8671.189329.9276.688DF days to flowering, LFL length of flag leaf, BT Basal tillers, BM biomass, PWT panicle weight, GWT grain weight, HSM 100- seed weight, TH threshability, HIharvesting index.3.3.3.3 Mean comparisons for plant phenology and yield components. Mean comparisons (Table 3.8) showed that sorghum genotypes under well irrigated conditions reached flowering slightly early than the genotypes under drought stress conditions. Days to flowering was reduced under drought stress condition by 6.12. The overall mean for genotypes under well irrigated conditions was lower at 76.47days compared to 81.46days under waterstress conditions. The early line under water stress condition was wotecollection1 (56.04 days compared to IESV23006DL under well irrigated condition. Conversely, the late line under waterstress conditions were Amachiha2 (135.33 days) compared to Olodiong (125.04 days) under well irrigated conditions. Despite delayed flowering under water stress condition, genotype, Hariray, ICSVIII1N, IESV23010DL, Kibokolocal, Landiwhite, Nuerbai, Tabat and Wadahamed reached flowering early under waterstress condition than under well irrigated condition while flowering under both water regimes was attained at the same time byaccessionsBurialure (102 days), ICSR161(66.43 days) , Lodoharie (61.days), Lodoka1(90.06 days), PP290 (66.02 days). For all yield components, there was a significant means reduction under water stress conditions compared to well irrigated conditions. Length of flag leaf recorded mean reduction from 39.01cm to 33.8cm. Panicle weight was reduced from 62.28g to 50.28g but genotypes ICSR161, ICSVIII1N, IESV931131DL, IESV92029DL, IESV92170DL, Nolokidok, Tharaka11, and Wotecollection1 recorded higher panicle length under waterstress condition than under well irrigated condition. Grain yield was reduced from 41.14g to 32.8g. High grain weight under waterstress than control was exhibited by genotypes, Omuhathi, Nuerbai, Wadahamed, Alwala, Hariray, IESB2, AG8, Makuach, IESV23006DL, Malual, Kudokine, Lodoka2, Lodudu, ICSVIII1N, Deri2, Gwada, IESV92172DL, Mereselightbrown and IESV92003DL. 100-seed weight was reduced from 2.594g to 2.191g. Highest accessions under waterstress conditions than control was given by genotypes, Atahti, CR355, Hariray, Hugurtay, IESV92043DL, IESV92172DL, Jeri2, Kibokolocal, Kodukine, Lodokawhite, Lolikitha, Nolomutuk and Omuhathi. Threshability index recorded means reduction from 66.42g to 64.8g. Genotypes that recorded high threshability under waterstress conditions compared to well irrigated conditions were Akuorachot, Ber, CR355, ICSR161, IESB2, IESV931111DL, IESV23006DL, IESV92029DL, IESV92170DL, IESV92172DL, Jeri1, Lodoka1, Lodudu, Lolodoka2, Mahube, Majoldi, Makuach, Malual, Medenge, Mersebrownred, Mugeta, Nuerbai, Oludiong, Omuhathi, PP290, and Wadehamed. Harvesting index recorded means reduction from 5.28 to 4.43. The genotypes that showed increased harvest index under drought stress condition compared to well irrigated condition were, Alwala, Derijeri, Ibursar, ICSV111IN, IESV911104DL, IESV92172DL, Jeri1, Jeri2, Khalid, Lanidwhite, Lodoka1, Lodudu, Lolodoka1, Lowoikudopayam, Majoldi, Nohonyekhohoro, Nuerbai, Olodiong, Osmanassai and Tharaka6. Under waterstress (Table 3.9), Waxy bloom was positively and significantly correlated with threshability (r0.5658), panicle weight (r 0.0565), length of flag leaf (r 0.0893), biomass (r0.0579) and negatively significantly correlated with 100-seedweight (r -0.0697). Staygreen gave positive and highly significant correlation with harvesting index (r 0.0831), panicle widths (r 0.0493) and negatively correlated with peduncle length (r -0.0973). Panicle length was positively and highly significantly correlated with grain weight (r 0.741). Panicle widths gave positive and highly significant correlation with biomass (r 0.0623). Panicle length was positively and highly significantly correlated with peduncle exertion (r 0.549). Plant height showed positive and highly significant correlation with peduncle length (r 0.0656). Peduncle length gave positive and highly significant correlation with 100seedweight (r 0.0814). Harvesting index gave negatively and highly significant correlation with biomass (r – 0.6762) and grain weight (r -0.0728). 100-seedweight gave positive and highly significant correlation with grain weight (r 0.075). Days to 50 flowering was positively correlated with biomass (r 0.0576). Results of correlations for phenotypic traits under well irrigated condition are illustrated in Table 3.10. Threshability gave positive and highly significant correlation with 100-seedweight (r 0.0789), plant height (r 0.076) and negatively correlated with biomass (r 0.0575) and staygreen (r -0.0783). Panicle weight gave positive and highly significant correlation with biomass (r 0.5219), days to 50 flowering (r 0.05501), grain weight ( r 0.07642), panicle widths ( r 0.7759) and panicle length ( r 0.5013). Panicle showed positive and significant correlation with biomass (r 0.6412), days to 50 flowering (r 0.7011), peduncle length (r 0.6624), plant height (0.7759) and negatively correlated with harvesting index ( r -0.5463). Plant height gave positive and significant correlation with biomass (r 0.7792), days to 50 flowering (r 0.8528) and negative correlation with harvest index (r -0.5462). Peduncle exertion gave positive and highly significant correlation with days to flowering (r 0.0982), peduncle length ( r 0.6836). Peduncle length gave positive and significant correlation with biomass (r 0.5118), days to 50 flowering ( r 0.5144) and grain weight ( r 0.0922) and negative correlation with harvesting index ( r -0.5012). Harvesting index gave positive and highly significant correlation with grain weight (r 0.0641) and negative and significant correlation with biomass) r -0.5342) and days to 50 flowering (r -0.5091). Days to 50 flowering was positively correlated with biomass (r 0.752) (Table 3.10). Table 3.9 Correlation coefficients among the different traits under water stress condition THStGPWTPWIPLPHTPEXPELLGFLHiHSMGYDOFBMTH-StG0.2187ns-PWT-0.0492ns-0.0347ns-PWI-0.0309ns0.04930.3572ns-PL-0.2179ns-0.2068ns0.1772ns0.1021ns-PHT-0.2898ns-0.2503ns0.033ns-0.0192ns0.6096PEX-0.09730.039ns-0.1105ns0.2583ns0.1896ns0.348ns-PEL-0.1816ns-0.0932-0.0418ns0.1903ns0.54910.6560.7125-LFL-0.0493ns-0.129ns0.2611ns0.2458ns0.2159ns0.0211ns0.08750.084-Hi0.2711ns0.08310.3283ns0.1791ns0.0229ns0.0062ns0.0428ns-0.0198ns0.1652nsHSM0.2625ns0.1105ns-0.1122ns-0.0437ns-0.3003ns-0.2534ns0.0545-0.0814-0.1249ns0.0728-GWT0.516ns0.134ns0.7410.2754ns-0.005ns-0.1614ns-0.1274ns-0.1243ns0.1732ns0.4484ns0.075-DF-0.2733ns-0.3265ns-0.0319ns-0.2199ns0.4484ns0.7457-0.0209ns0.3259ns-0.1108ns-0.0728-0.3003ns-0.1676ns-FBM-0.0215ns-0.0114ns0.0178ns-0.06230.0678-0.0166ns-0.0903-0.0212ns-0.0301ns-0.6762-0.1268ns-0.0093ns0.0576- TH threshability, StG staygreen, PWT panicle weight, PWI panicle width, PL panicle length, PHT plant height, PEX peduncle exertion, PEL peduncle length, LFL length of flag leaf,, HI harvesting index, HSM 100-seed weight GWT grain weight, DF days to flowering and BM fresh biomass Table 3.10 Correlation coefficients among the different traits under well irrigated condition THStGPWTPWIPLPHTPEXPELLFLHSMHIGWTDFBMTH-StG-0.0783-PWT-0.1167ns0.096-PWI-0.1551ns0.06790.0954-PL-0.1743ns0.1164ns0.50130.2226ns-PHT-0.08260.1224ns0.494ns0.0438ns0.7759PEX-0.0405ns-0.0283ns-0.1085ns0.1591ns0.2226ns0.3279ns-PEL-0.06150.0392ns0.161ns0.1392ns0.66240.71280.6836-LFL-0.1111ns0.0174ns0.3919ns0.2593ns0.4131ns0.2489ns0.0333ns0.129ns-HSM0.0789-0.0213ns-0.2694ns-0.1607ns-0.3621ns-0.391ns-0.2464ns-0.3388ns-0.1967nsHI0.3709ns-0.0359ns-0.2116ns-0.0384ns-0.5463-0.6331-0.326ns-0.5612-0.2132ns0.2406ns-GWT0.4882ns0.06760.76420.006ns0.3243ns0.3622ns-0.1222ns0.09220.2537ns-0.2039ns0.0641-DF-0.08490.1547ns0.5501-0.0184ns0.70110.85280.09820.51440.3297ns-0.3738ns-0.50910.4049ns-BM-0.05750.0137ns0.5218-0.0004ns0.64120.77920.1998ns0.51180.3463ns-0.3317ns-0.63420.4072ns0.752-TH threshability, StG staygreen, PWT panicle weight, PWI panicle width, PL panicle length, PHT plant height, PEX peduncle exertion, PEL peduncle length, LFL length of flag leaf, HI harvesting index, HSM 100-seed weight GWT grain weight, DF days to flowering and BM fresh biomass.3.6 Discussions 3.6.1 Morphological characters Genotypes and water regimes had effects on staygreen score, dry leaf scores, waxy bloom, leaf area, leaf rolling, total leaf count and lodging. This confirmed the wider variability among the genotypes under this study. The interaction between water regimes and genotypes differed significantly for staygreen, leaf rolling, leaf area and lodging, implying that water stress affects the different traits. In this study, the absence of effect of interaction on total leaf counts and dry leaf scores suggested the stability of these traits under post-flowering water stress condition. The current study identified the genotypes Olerere (1.963) and Omuhathi (7.882) showing susceptibility to senescence. These results are in line with ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1111/nph.14059, author dropping-particle , family Rebetzke, given Greg J, non-dropping-particle , parse-names false, suffix , dropping-particle , family Jimenez-berni, given Jose A, non-dropping-particle , parse-names false, suffix , dropping-particle , family Bovill, given William D, non-dropping-particle , parse-names false, suffix , dropping-particle , family Deery, given David M, non-dropping-particle , parse-names false, suffix , dropping-particle , family James, given Richard A, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2016 , page 4919-4924, title High-throughput phenotyping technologies allow accurate selection of stay-green, type article-journal , uris http//www.mendeley.com/documents/uuid435f024d-329b-416e-8ef5-65e744f4ead3 , id ITEM-2, itemData DOI 10.4236/ajps.2015.69141, ISSN 2158-2742, abstract Sorghum (Sorghum bicolour (L.) Moench) grown under rain-fed conditions is usually affected by drought stress at different stages, resulting in reduced yield. The assessment of variation in mor-pho-physiological traits contributing towards drought tolerance at these stages is of vital impor-tance. This study was conducted using a split plot design with three replications to evaluate 25 sorghum accessions at post flowering stage under well watered and drought stress conditions at Hamelmalo Agricultural College. The data of 14 different morpho-physiological traits were sub-jected to analysis of variance, estimation of genetic variability and heritability and principal com-ponent analysis. We analyzed variance for seedling vigor, number of leaves, leaf area, stay-green, peduncle exsertion, panicle length and width, plant height, days to flowering and maturity, grain yield, biomass and harvest index under drought stress and irrigated conditions. The results showed that genotypic differences were significant at P 0.05 – 0.001. High magnitude of phe-notypic and genotypic coefficient of variations for plant height, harvest index and biomass as well as high heritability for days to flowering, panicle length, days to maturity and over all agronomic score were recorded. Principal component (PC) analysis showed that the first 4 PCs had Eigen value 1 explaining 74.6 of the total variation with grain yield, biomass, stay-green, leaf area, peduncle exsertion and days to flowering and maturity being the most important characters in PC1 and PC2. This research demonstrated high diversity for the characters studied. Moreover, the result showed that drought stress reduced the yield of some genotypes, though others were tole-rant to drought. Accessions EG 885, EG 469, EG 481, EG 849, Hamelmalo, EG 836 and EG 711 were Corresponding author. Tesfamichael et al. 1411 identified as superior for post-flowering drought tolerance and could be used by breeders in im-provement programs., author dropping-particle , family Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, given Aggrey Bernard Nyende2, non-dropping-particle , parse-names false, suffix , container-title American Journal of Plant Sciences, id ITEM-2, issue 6, issued date-parts 2015 , page 1410-1424, title Genetic Variation among Sorghum (Sorghum bicolor L. Moench) Landraces from Eritrea under Post-Flowering Drought Stress Conditions, type article-journal, volume 6 , uris http//www.mendeley.com/documents/uuid89f1c00f-d432-45c5-a43a-6755b0404895 , mendeley formattedCitation (Rebetzke, Jimenez-berni, Bovill, Deery, James, 2016 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015), manualFormatting Tesfamichael et al., (2015) Rebetzke, ( 2016), plainTextFormattedCitation (Rebetzke, Jimenez-berni, Bovill, Deery, James, 2016 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015), previouslyFormattedCitation (Rebetzke, Jimenez-berni, Bovill, Deery, James, 2016 Tesfamichael Abraha1, 2, Stephen Mwangi Githiri2, Remmy Kasili2, Woldeamlak Araia1, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Tesfamichael et al., (2015) Rebetzke, ( 2016) who reported the existence of substantial variability among sorghum landraces for staygreen attributable to genetic and environmental influence. The correlation coefficient revealed that staygreen was positively correlated with panicle weight, grain yield, 100-seed weight and harvesting index. Previous findings by ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erw276, author dropping-particle , family Christopher, given John T, non-dropping-particle , parse-names false, suffix , dropping-particle , family Christopher, given Mandy J, non-dropping-particle , parse-names false, suffix , dropping-particle , family Borrell, given Andrew K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Fletcher, given Susan, non-dropping-particle , parse-names false, suffix , dropping-particle , family Chenu, given Karine, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 17, issued date-parts 2018 , page 5159-5172, title Stay-green traits to improve wheat adaptation in well- watered and water-limited environments, type article-journal, volume 67 , uris http//www.mendeley.com/documents/uuidf101c010-01eb-4fd1-9cb8-92820e975b2c , mendeley formattedCitation (Christopher, Christopher, Borrell, Fletcher, Chenu, 2018), manualFormatting Christopher et al., (2018), plainTextFormattedCitation (Christopher, Christopher, Borrell, Fletcher, Chenu, 2018), previouslyFormattedCitation (Christopher, Christopher, Borrell, Fletcher, Chenu, 2018) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Christopher et al., (2018) reported a positive correlation between grain yield and staygreen trait. The existence of positive correlation between these traits implied that selection for the stay green trait is possible during screening experiments. This is because staygreen genotypes can easily be distinguished from water stress sensitive genotypes on the basis of senescence ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Sakhi, given Shazia, non-dropping-particle , parse-names false, suffix , dropping-particle , family Rehman, given Shafiq, non-dropping-particle , parse-names false, suffix , dropping-particle , family Okuno, given Kazutoshi, non-dropping-particle , parse-names false, suffix , dropping-particle , family Shahzad, given Armaghan, non-dropping-particle , parse-names false, suffix , dropping-particle , family Jamil, given Mohammad, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2014 , page 251-260, title Evaluation of Sorghum ( Sorghum bicolor ) Core Collection for Drought Tolerance Pollen Fertility and Mean Performance of Yield Traits and Its Components at Reproductive Stage, type article-journal , uris http//www.mendeley.com/documents/uuid082d08ac-086c-41e4-9957-63d164bf4a1d , mendeley formattedCitation (Sakhi, Rehman, Okuno, Shahzad, Jamil, 2014), manualFormatting (Sakhi et al., 2014), plainTextFormattedCitation (Sakhi, Rehman, Okuno, Shahzad, Jamil, 2014), previouslyFormattedCitation (Sakhi, Rehman, Okuno, Shahzad, Jamil, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sakhi et al., 2014). The dry leaf scores (DLS) were estimated for all genotypes under water stress to screen for accessions with stable staygreen trait whereby the genotype Olerere (12.82) exhibiting the lowest DLS while Omuhathi (76.23) showed the highest senescence. Variability among sorghum genotypes for dry leaf score (DLS) has been reported previously by ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Sakhi, given Shazia, non-dropping-particle , parse-names false, suffix , dropping-particle , family Rehman, given Shafiq, non-dropping-particle , parse-names false, suffix , dropping-particle , family Okuno, given Kazutoshi, non-dropping-particle , parse-names false, suffix , dropping-particle , family Shahzad, given Armaghan, non-dropping-particle , parse-names false, suffix , dropping-particle , family Jamil, given Mohammad, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2014 , page 251-260, title Evaluation of Sorghum ( Sorghum bicolor ) Core Collection for Drought Tolerance Pollen Fertility and Mean Performance of Yield Traits and Its Components at Reproductive Stage, type article-journal , uris http//www.mendeley.com/documents/uuid082d08ac-086c-41e4-9957-63d164bf4a1d , mendeley formattedCitation (Sakhi et al., 2014), manualFormatting Sakhi et al. (2014), plainTextFormattedCitation (Sakhi et al., 2014), previouslyFormattedCitation (Sakhi et al., 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Sakhi et al. (2014). The large variation for DLS observed may be attributed to broader genetic diversity of the accessions involved in this study. The landraces Lowoikudopayam (13.34) and Meresebrownred (20.09 assembled from South Sudan outperformed the check variety Macia with DLS of 25.74. The importance of the staygreen trait is in reducing the canopy size at flowering by modifying leaf numbers and leaf size to scale down pre-flowering water use in order to conserve water for grain filling under post-anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, author dropping-particle , family Borrell, given Andrew K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Mullet, given John E, non-dropping-particle , parse-names false, suffix , dropping-particle , family George-jaeggli, given Barbara, non-dropping-particle , parse-names false, suffix , dropping-particle Van, family Oosterom, given Erik J, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development , leaf anatomy , root growth , and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid4cab7664-6a04-4a20-b3f4-232d600b02c2 , mendeley formattedCitation (A. K. Borrell, Mullet, George-jaeggli, Oosterom, 2014), manualFormatting (Borrell et al.,2014), plainTextFormattedCitation (A. K. Borrell, Mullet, George-jaeggli, Oosterom, 2014), previouslyFormattedCitation (A. K. Borrell, Mullet, George-jaeggli, Oosterom, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al.,2014). With regard to the total leaf counts, no variation was observed across the water regimes implying that the post-anthesis waterstress had no effect. Research finding by ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.2135/cropsci2000.4041026x, author dropping-particle , family Borrell, given Andrew, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue July, issued date-parts 2000 , title Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought I . Leaf Growth and Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought , type article-journal , uris http//www.mendeley.com/documents/uuid65dd2e28-15d2-480e-bcaa-58f578012f0b , mendeley formattedCitation (A. Borrell, 2000), manualFormatting Borrell, (2000), plainTextFormattedCitation (A. Borrell, 2000), previouslyFormattedCitation (A. Borrell, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Borrell, (2000) stated that large leaf area among landraces serves as an important photosynthetic machinery for harvest of high photosynthate vital for running essential processes of the plant. Reduced total leaf counts and net leaf area were observed among improved staygreen lines namely IESV92028DL IESV91111DL, Mahube, IESV92172DL, Gwada and IESV23010DL. Previous research observed reduced leaf numbers per culm and leaf area which were linked to increased grain yield under post anthesis drought stress ( ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.3389/fphys.2012.00347, ISBN 1664-042X (Electronic)r1664-042X (Linking), ISSN 1664042X, PMID 23049510, abstract Improving crops yield under water-limited conditions is the most daunting challenge faced by breeders. To this end, accurate, relevant phenotyping plays an increasingly pivotal role for the selection of drought-resilient genotypes and, more in general, for a meaningful dissection of the quantitative genetic landscape that underscores the adaptive response of crops to drought. A major and universally recognized obstacle to a more effective translation of the results produced by drought-related studies into improved cultivars is the difficulty in properly phenotyping in a high-throughput fashion in order to identify the quantitative trait loci that govern yield and related traits across different water regimes. This review provides basic principles and a broad set of references useful for the management of phenotyping practices for the study and genetic dissection of drought tolerance and, ultimately, for the release of drought-tolerant cultivars., author dropping-particle , family Tuberosa, given Roberto, non-dropping-particle , parse-names false, suffix , container-title Frontiers in Physiology, id ITEM-1, issue September, issued date-parts 2012 , page 1-26, title Phenotyping for drought tolerance of crops in the genomics era, type article-journal, volume 3 SEP , uris http//www.mendeley.com/documents/uuidec401d45-759b-457c-800b-c320213a879b , mendeley formattedCitation (Tuberosa, 2012), manualFormatting Tuberosa, 2012, plainTextFormattedCitation (Tuberosa, 2012), previouslyFormattedCitation (Tuberosa, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Tuberosa, 2012 Borrell et al., 2014). This can be explained by the fact that the Staygreen genotypes minimized water use during the pre-anthesis phase so as to conserve water for grain filling during the grain development phase leading to high yields ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015, plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Borrell et al., 2014). The accession Burialure is a drought susceptible, tall and moderately yielding genotypes which easily lodged. The high vulnerability to lodging could be associated with high senescence observed coupled with its plant height and stem girth. Similar observations have been made in previous studies ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1080/02571862.2002.10634434, ISSN 02571862, author dropping-particle , family McLaren, given N. W., non-dropping-particle , parse-names false, suffix , container-title South African Journal of Plant and Soil, id ITEM-1, issue 1, issued date-parts 2002 , page 37-42, title Evaluation of sorghum hybrids for resistance to the root rot complex, type article-journal, volume 19 , uris http//www.mendeley.com/documents/uuida7216a1b-69ff-42b4-8e5f-be07cc6dd08f , mendeley formattedCitation (McLaren, 2002), plainTextFormattedCitation (McLaren, 2002), previouslyFormattedCitation (McLaren, 2002) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (McLaren, 2002) ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Thomas Ougham, 2014b), manualFormatting Thomas and Ougham, 2014), plainTextFormattedCitation (Thomas Ougham, 2014b), previouslyFormattedCitation (Thomas Ougham, 2014b) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Thomas and Ougham, 2014). 3.6.2 Physiological characters The wax load was denser under waterstress condition than under controlled conditions. Dense wax load under drought stress condition has been associated with cuticular wax biosynthesis translocation, composition and density and are influenced solely by environmental factors including solar radiation, temperature, moisture, and humidity in sorghum ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.3389/fpls.2017.00621, author dropping-particle , family Xue, given Dawei, non-dropping-particle , parse-names false, suffix , dropping-particle , family Zhang, given Xiaoqin, non-dropping-particle , parse-names false, suffix , dropping-particle , family Lu, given Xueli, non-dropping-particle , parse-names false, suffix , dropping-particle , family Chen, given Guang, non-dropping-particle , parse-names false, suffix , dropping-particle , family Chen, given Zhong-hua, non-dropping-particle , parse-names false, suffix , dropping-particle , family Chen, given Zhong-hua, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue April, issued date-parts 2017 , page 1-12, title Molecular and Evolutionary Mechanisms of Cuticular Wax for Plant Drought Tolerance, type article-journal, volume 8 , uris http//www.mendeley.com/documents/uuid1d0a3d12-e4d1-4618-9b0f-46aea19568fa , mendeley formattedCitation (Xue et al., 2017), manualFormatting (Xue et al., 2017), plainTextFormattedCitation (Xue et al., 2017), previouslyFormattedCitation (Xue et al., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Xue et al., 2017). The accessions that scored dense wax load under drought stress condition were Gwada, ICSR161, Mahube, AG8, IESV91131DL, IESV91111DL, IESV92028DL and IESV92172DL and comprised of lines drawn from ICRISAT- Nairobi gene bank. In this study, genotypes with dense wax were superior for water stress tolerance and grain yields relative to non-waxy accessions. Borrell et al.,(2014) reported the existence of significant correlations between wax contents and water stress tolerance among staygreen genotypes. The accessions that gave leaf rolling were late maturing landraces assembled from South Sudan. The leaf rolling trait is associated with diminished water potential and low leaf turgor attributed to poor osmotic adjustment (Chaanappaoudeer et al., 2007). The leaf rolling was severe among the late accessions which may be attributed to the fact that irrigation water was withheld at 50 per cent flowering when these accessions were still at vegetation phase of growth. 3.6.3 Assessment of earliness in South Sudan sorghum germplasm Significant variability among the accessions for days to flowering was observed among the evaluated sorghum genotypes. Delayed flowering under drought stress has been reported by ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Menezes1, given C.B., non-dropping-particle , parse-names false, suffix , dropping-particle , family Saldanha2, given D.C., non-dropping-particle , parse-names false, suffix , dropping-particle , family , C.V. Santos3 , L.C. Andrade3 , M.P. Mingote Ju00falio3, given A.F. Portugal1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Tardin1, given and F.D., non-dropping-particle , parse-names false, suffix , dropping-particle , family 1, given , non-dropping-particle , parse-names false, suffix , container-title Genetics and Molecular Research, id ITEM-1, issue 4, issued date-parts 2015 , page 12675-12683, title Evaluation of grain yield in sorghum hybrids under water stress, type article-journal, volume 14 , uris http//www.mendeley.com/documents/uuida216682f-03f9-4a92-864e-cab7ccda40da , mendeley formattedCitation (Menezes1, Saldanha2, , C.V. Santos3 , L.C. Andrade3 , M.P. Mingote Ju00falio3, Tardin1, 1, 2015), manualFormatting Menezes et al., (2015 ), plainTextFormattedCitation (Menezes1, Saldanha2, , C.V. Santos3 , L.C. Andrade3 , M.P. Mingote Ju00falio3, Tardin1, 1, 2015), previouslyFormattedCitation (Menezes1, Saldanha2, , C.V. Santos3 , L.C. Andrade3 , M.P. Mingote Ju00falio3, Tardin1, 1, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Menezes et al., (2015 ) who recorded 2 retardation in days to flowering. Drought effect on plant phenology has been associated with delayed flowering and physiological maturity when drought stress was imposed at booting stage (Tesfamicheal et al., 2015 Seetharama and Bidinger et al., 1977). The superior lines that outperformed the check variety for earliness were Wotecollection1 (56.94days), IESV23010DL (58.06days, ZSV3 (60.09days), Bizany (61.17days) and Tabat (61.17days). However, there were yield penalties observed among the accessions wotecollection1, Bizany, ZSV3 and Tabat. Thus, the accessions IESV23010DL would best serve as an ideal drought evading candidate with better performance for grain yield. Early flowering under waterstress than control was observed among accessions, Hariray, ICSVIII1N, IESV23010DL, Kibokolocal, Landiwhite, Nuerbai, Tabat and Wadahamed which is an indicative of tolerance. Early flowering under waterstress has been reported by ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , mendeley formattedCitation (Dalal, 2012), manualFormatting Dalal, (2012) Dalal et al., (2015), plainTextFormattedCitation (Dalal, 2012), previouslyFormattedCitation (Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Dalal, (2012) Dalal et al., (2015) who attributed it to rapid phenological development and development plasticity among drought evading accessions. 3.6.4 Assessment of yield in South Sudan sorghum germplasm The growth components namely plant height, stem girth, peduncle length, peduncle exertion, panicle width, panicle length and biomass showed significant effects across the genotypes and water regimes. No reduction of growth components was observed under controlled treatment because of presence of optimal conditions for growth and development as opposed to the water stressed environment. Reduction of growth components due to water stress has been reported in previous studies ADDIN CSL_CITATION citationItems id ITEM-1, itemData ISSN 0976-1233, abstract _____________________________________________________________________________________________ ABSTRACT In this research effect of Eucalyptus camaldulensis L. leaves compose as biotic stress in ratio 0,(control), 4 and 8 (w/w) with soil and drought as abiotic stress include 25 and 10 of soil saturation capacity on growth parameters of Sorghum were studied. Sorghum bicolor var. Speed feed seeds were planted under pots condition in photoperiods 21 u00b1 1 u00baC and 14u2013 h light /10 u2013h dark. 30 days after planting were separated root from shoot and growth parameters were determined. The results showed that length, fresh and dry weight of root and shoot, number and area of sorghum leaves to application of decompose of Eucalyptus leaf in ratio 4and 8 with soil were significantly decreased. Also mild and sever stress of drought also reduced growth parameters in root and shoot of Sorghum in comparison to control . Our data showed the growth reduction in Sorghum is more severe by Eucalyptus leaf decompose as biotic stress in comparison to drought stress as abiotic stress., author dropping-particle , family Niakan, given Maryam, non-dropping-particle , parse-names false, suffix , dropping-particle , family Darvishkhezri, given Mahmood, non-dropping-particle , parse-names false, suffix , dropping-particle , family Iranbakhsh, given Alireza, non-dropping-particle , parse-names false, suffix , dropping-particle , family Barzegar, given Ali, non-dropping-particle , parse-names false, suffix , container-title Scholars Research Library Annals of Biological Research, id ITEM-1, issue 6, issued date-parts 2013 , page 18-22, title Changes of Sorghum growth in response to drought and allelopathy stresses, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuid9a9f04fb-c72b-4383-8041-1bad7c569ea8 , mendeley formattedCitation (Niakan, Darvishkhezri, Iranbakhsh, Barzegar, 2013), manualFormatting (Niakan et al., 2013), plainTextFormattedCitation (Niakan, Darvishkhezri, Iranbakhsh, Barzegar, 2013), previouslyFormattedCitation (Niakan, Darvishkhezri, Iranbakhsh, Barzegar, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Niakan et al., 2013).The reduction in plant height and stem girth is linked to low water intake and decline in net water potential created by poor osmotic adjustment ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A. Bibi, H. A. Sadaqat, given M. H. N. Tahir and H. M. Akram, non-dropping-particle , parse-names false, suffix , container-title The Journal of Animal and Plant Sciences, id ITEM-1, issue 3, issued date-parts 2012 , page 2-8, title SCREENING OF SORGHUM ( Sorghum bicolor Var Moench ) FOR DROUGHT TOLERANCE AT SEEDLING STAGE IN POLYETHYLENE GLYCOL ., type article-journal, volume 22 , uris http//www.mendeley.com/documents/uuidbcb66e08-f58a-4e4a-bd5b-6461ae46e630 , mendeley formattedCitation (A. Bibi, H. A. Sadaqat, 2012), manualFormatting (Bibi, 2012), plainTextFormattedCitation (A. Bibi, H. A. Sadaqat, 2012), previouslyFormattedCitation (A. Bibi, H. A. Sadaqat, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Bibi, 2012). Reduction in peduncle length and peduncle exertion is attributed to low leaf water potential which does not allow plants to maintain the extension of peduncle from the sheath under severe drought stress condition. Longer peduncle length and peduncle exertion was scored by accession Lodoka2 and Natari again, it is an indicative of tolerance. Biomass is an important trait associated with grain yield and staygreen trait. The reduction in biological yield is due to reduced growth and net assimilation rates in drought sensitive genotypes (ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erw276, author dropping-particle , family Christopher, given John T, non-dropping-particle , parse-names false, suffix , dropping-particle , family Christopher, given Mandy J, non-dropping-particle , parse-names false, suffix , dropping-particle , family Borrell, given Andrew K, non-dropping-particle , parse-names false, suffix , dropping-particle , family Fletcher, given Susan, non-dropping-particle , parse-names false, suffix , dropping-particle , family Chenu, given Karine, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 17, issued date-parts 2018 , page 5159-5172, title Stay-green traits to improve wheat adaptation in well- watered and water-limited environments, type article-journal, volume 67 , uris http//www.mendeley.com/documents/uuidf101c010-01eb-4fd1-9cb8-92820e975b2c , mendeley formattedCitation (Christopher et al., 2018), manualFormatting Christopher et al., 2018, plainTextFormattedCitation (Christopher et al., 2018), previouslyFormattedCitation (Christopher et al., 2018) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Christopher et al., 2018 Bibi, 2012). Staygreen accessions gave high biological yield with improved staygreen elite lines such as Mahube, IESV91131DL, and Gadamhamam topping the list followed by staygreen landraces, Mereselightbrown, Lodoka2 and Olerere. These findings corroborate those by previous researchers who reported that water stress reduction of biomass depends on the characteristics of the genotypes and the phenological stage at which it occurred ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Mendoza-castillo, given M C, non-dropping-particle , parse-names false, suffix , dropping-particle , family Huerta, given A J, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , page 149-156, title Biomass production and grain yield of three sorghum lines differing in drought resistance Producciu00f3n de biomasa y rendimiento de grano de tres lu00edneas de sorgo que difieren en su resistencia a sequu00eda, type article-journal, volume 9457 , uris http//www.mendeley.com/documents/uuid35dff833-cfb4-4da2-a1ad-60ed11b4bdf3 , mendeley formattedCitation (Mendoza-castillo Huerta, 2012), manualFormatting (Mendoza and Huerta, 2012), plainTextFormattedCitation (Mendoza-castillo Huerta, 2012), previouslyFormattedCitation (Mendoza-castillo Huerta, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Mendoza and Huerta, 2012). 3.6.5 Yield components The yield and related components namely length of flag leaf, panicle weight, grain weight, 100-seedweight and harvesting index, threshability and basal tillers showed significant variations. There were water stress related percentage reductions which have also been reported by Sandoval, (1989). Drought stress causes yield reduction by decreasing grain weight 100-seeed weight through reduction in seed per spikelet, biomass and floret abortion ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Hameed, given Rasha A, non-dropping-particle , parse-names false, suffix , dropping-particle , family Nouri, given Ahmed, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2000 , title Performance of selected sorghum (, type article-journal , uris http//www.mendeley.com/documents/uuid622ef29d-5aae-4f33-bced-8c836edf7c90 , mendeley formattedCitation (Hameed Nouri, 2000), manualFormatting (Hameed and Nouri, 2000), plainTextFormattedCitation (Hameed Nouri, 2000), previouslyFormattedCitation (Hameed Nouri, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Hameed and Nouri, 2000). The flag leaf plays an important role of filling grain under drought stress condition thus the reduction in length of flag leaf may be due to drought stress effect on cell division which ultimately inhibits leaf elongation under declined leaf water potential (Hsalaoand Henderson, 1979). Only the accession Alwala recorded longer flag leaf length) 33.71cm) under stress condition compared to reduced length (23.73cm) under control implying tolerance to water stress. Panicle weight reduction was significantly high under waterstress condition with accession Lobuheti expressing better performance for panicle weight (75.92g). Reduction in panicle weight is attributed to low growth arising from reduced photosynthetic activity (Sandoval et al., 1989). The genotypes Lobuheti (50.65g), IESV91131DL (46.52g), Lodoka1 (47.08g) and IESV92172DL (46.69g) showed superior field weights as opposed to the check variety. These accessions had high stay green rating. Similar results have been reported associating the stay green trait with high yield (ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erv405, author dropping-particle , family Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, given Antoni R. Slabas1 and Marc R. Knight1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 22, issued date-parts 2015 , page 7061-7073, title Transcriptomic analysis comparing stay-green and senescent Sorghum bicolor lines identifies a role for proline biosynthesis in the stay-green trait, type article-journal, volume 66 , uris http//www.mendeley.com/documents/uuidad1a3d23-9955-4374-a05c-af92a8e1fa40 , mendeley formattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015), manualFormatting Rosenow et al., 1983 Borrell et al., 2000 Stephanie et al.,2015 Tao et al., 2000), plainTextFormattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015), previouslyFormattedCitation (Stephanie M. Johnson1, Ian Cummins1,, Fei Ling Lim2,, 2015) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Rosenow et al., 1983 Borrell et al., 2000 Stephanie et al.,2015 Tao et al., 2000). Means results showed that cessions IESV91131DL, IESV92172DL, and Lobuheti were also superior for 100-seed weight. 100-seedweight is an important economic trait in South Sudan where grain marketing depends on grain weight. These accessions are ideal varieties for both subsistence and commercial farming in drought prone agro-ecologies of South Sudan. Although accession Lodoka performed well with regard to grain yield and staygreen rating, it is a late line that takes up to 112.03 days to reach physiological maturity. Therefore, it needs further improvement for earliness. Among yield contributing components, harvesting index and threshability are considered key determinants of the final grain yield. Accession IESV91131DL and IESV92172DL recorded high harvesting index (3.13 and 6.86) and threshing percentage of 73.94 and 67.34. This confirms their yield stability under drought stress condition. Results of correlation coefficient revealed that panicle weight showed positive correlation with grain yield, harvesting index, and panicle width. The existence of significant correlation coefficients between these traits means that selection for grain yield can be based on integral selection for these traits. Similarly, threshability was positively correlated with grain yield, harvesting index and staygreen implying that these traits can be selected together when screening for varieties with relatively high threshing percentage. CHAPTER FOUR COMBINING ABILITY FOR EARLINESS, YIELD AND DROUGHT TOLERANCE AMONG F1 SORGHUM GENOTYPES 4.1 Introduction. Drought avoidance is the plant ability to survive low tissue water content in drought stress condition ADDIN CSL_CITATION citationItems id ITEM-1, itemData abstract Before attempting to address this subject it isnimportant to define what is understood by temperaturenstress. It is a complex subject which hasnrecently been reviewed in three books (Lyons etnal. 1979 Levitt 1980 Turner and Kramer 1980)ntherefore definitions and details of the physiologicalnand biochemical processes associated withntemperature stress will not be given here. In brief,nhowever, a quantitative definition of temperaturenstress in sorghum, as in any crop, is difficult tonprovide since it will depend on a number of factorsnich will include the duration of exposure ofneither high or low temperature, the activity ornstage of growth of the exposed tissue and finallynthe thermal adaptation of the particular sorghumncultivar., author dropping-particle , family Peacock, given J M, non-dropping-particle , parse-names false, suffix , container-title International Crops Research lnstltute for the Semi-Arid Tropics 1982 Sorghum in the Eighties Proceedings of the International Symposium on Sorghum, id ITEM-1, issued date-parts 1982 , page 143-158, title Response and Tolerance of Sorghum to Temperature Stress, type article-journal , uris http//www.mendeley.com/documents/uuidd606494b-5b15-4483-b0ef-0eeadc4d3f04 , mendeley formattedCitation (Peacock, 1982), plainTextFormattedCitation (Peacock, 1982), previouslyFormattedCitation (Peacock, 1982) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Peacock, 1982). The fundamental basis of drought tolerance is staygreen trait which enhances plant growth and reproduction under drought stress conditions ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Walulu, given Richard Sikuku, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1991 , title GENETIC CONTROL OF POST-FLOWERING DROUGHT TOLERANCE ( STAY GREEN ) IN SORGHUM by IN Submitted to the Graduate Faculty of Texas Tech University in Part i a 1 F u 1 f i 11 men t of the Requirements for the Degree of HASTER OF SCIENCE Approved, type article-journal , uris http//www.mendeley.com/documents/uuid9dc708ca-7067-406a-995a-2b7188df49f0 , mendeley formattedCitation (Walulu, 1991), manualFormatting (Walulu, 1991 Staggenborg, 2010), plainTextFormattedCitation (Walulu, 1991), previouslyFormattedCitation (Walulu, 1991) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Walulu, 1991 Staggenborg, 2010). The stay green trait enhances foliar greenness during graining fill phase to physiological maturity under post anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular Biology, id ITEM-1, issued date-parts 2002 , page 713-714, title Mapping QTLs associated with drought resistance in sorghum ( Sorghum bicolor L . Moench ), type article-journal, volume 2000 , uris http//www.mendeley.com/documents/uuid70bc6d30-a5b5-48c1-bfc6-26179f4ec36c , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), manualFormatting (Rosenow et al., 2002), plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Rosenow et al., 2002). It is an important trait associated with drought tolerance in several plants including sorghum crop and it also enhances disease resistance while reducing the severity of lodging ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Dalal, given Monika, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue May 2015, issued date-parts 2012 , title Sorghum Improvement of Abiotic Stress Tolerance, type article-journal , uris http//www.mendeley.com/documents/uuidc398590b-2a2d-442e-9455-fa5df202ed7c , id ITEM-2, itemData author dropping-particle , family Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4, given David R. Jordan1, non-dropping-particle , parse-names false, suffix , dropping-particle , family Hammer2, given Patricia E. Klein5 and Graeme L., non-dropping-particle , parse-names false, suffix , id ITEM-2, issued date-parts 2014 , page 817-830, title Stay-green alleles individually enhance grain yield in sorghum under drought by modifying canopy development and water uptake patterns, type article-journal , uris http//www.mendeley.com/documents/uuiddd3081ad-71c8-4721-ae5c-af5412321ea0 , mendeley formattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012), manualFormatting (Borrell et al., 2014 Dalal, 2012), plainTextFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012), previouslyFormattedCitation (Andrew K. Borrell1, Erik J. van Oosterom2, John E. Mullet3, Barbara George-Jaeggli4 Hammer2, 2014 Dalal, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Dalal, 2012). It has a key role in source – sink reduction by reducing canopy size through reduced tillering, increased size of lower leaves, reduced size of upper leaves and reduction of number of leave per culm hence aid to minimize transpiration water loss and water demanding sink-sources ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2011Thomas and Ougham, 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2011Thomas and Ougham, 2014). The better yield performance among staygreen genotypes is due in part to their high efficiency in converting absorbed water into biomass and grain yield as well as sustained photosynthate flow through sustained stability of chloroplast and photosynthetic machinery sunder stress condition ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/erl225, author dropping-particle , family Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, given Robert Klein7 and John Mullet1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 2, issued date-parts 2018 , page 327-338, title Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence, type article-journal, volume 58 , uris http//www.mendeley.com/documents/uuid074f286e-a9c2-4331-81ad-947594116eac , mendeley formattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018), manualFormatting (Beyene et al., 2015 Borrell, 2000 Tesfamichael et al., 2015 Harris et al., 2018), plainTextFormattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018), previouslyFormattedCitation (Karen Harris1, P. K. Subudhi2, Andrew Borrell3,, David Jordan3, Darrell Rosenow4, Henry Nguyen5, Patricia Klein6, 2018) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Borrell, 2000 Tesfamichael et al., 2015 Harris et al., 2018). Staygreen trait is governed by a major gene ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Walulu, given Richard Sikuku, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1991 , title GENETIC CONTROL OF POST-FLOWERING DROUGHT TOLERANCE ( STAY GREEN ) IN SORGHUM by IN Submitted to the Graduate Faculty of Texas Tech University in Part i a 1 F u 1 f i 11 men t of the Requirements for the Degree of HASTER OF SCIENCE Approved, type article-journal , uris http//www.mendeley.com/documents/uuid9dc708ca-7067-406a-995a-2b7188df49f0 , mendeley formattedCitation (Walulu, 1991), plainTextFormattedCitation (Walulu, 1991), previouslyFormattedCitation (Walulu, 1991) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Walulu, 1991). Recent advances in genetic mapping has discovered four main staygreen QTLs namely Stg2, Stg1, Stg3 and Stg4 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family Nguyen, given P.K. Subudhi. D.T. Rosenow. H.T, non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid60445dda-f1f5-49ce-97d9-afb55d935112 , mendeley formattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), manualFormatting (Subudhi et al.,2000), plainTextFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000), previouslyFormattedCitation (P. K. S. D. T. R. H. . Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Subudhi et al.,2000). These staygreen QTLs confer staygreen trait, earliness and yield ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, given 3, non-dropping-particle , parse-names false, suffix , container-title Plant Molecular BiologyrSpecial issue Cereal genomics, id ITEM-1, issue 5/6, issued date-parts 2002 , page 713-726, title Mapping QTLs associated with drought resistance in sorghum (Sorghum bicolor L. Moench), type article-journal, volume 48 , uris http//www.mendeley.com/documents/uuidd32b46f7-c950-4765-b4b5-eb0a3b53fedd , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , mendeley formattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015 Sanchez et al., 2002 , plainTextFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (A.C. Sanchez1, P.K. Subudhi1, 2, D.T. Rosenow3 and H.T. Nguyen1, 2002b Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015 Sanchez et al., 2002 ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1007/s001220051538, ISBN 0040-5752, ISSN 0040-5752, abstract Stay green in sorghum (Sorghum bicolor L. Moench) is characterized by the plants ability to tolerate post-flowering drought stress, thereby delaying the premature leaf and plant death. It contributes to normal grain filling and reduces the incidence of stalk lodging and charcoal rot disease during the late stages of grain development. Breeding for improving post-flowering drought tolerance in sorghum hybrids remains an important objective of sorghum breeders. Since evaluation of the stay green response is difficult and unreliable under field conditions, due to the timing and intensity of moisture stress and large environmental interaction, progress in improving drought tolerance by conventional breeding methods has been slow. The objective of the present study was to determine the consistency of quantitative trait loci (QTLs) controlling stay green in sorghum. We re-evaluated the Recombinant Inbred Line (RIL)-mapping population from the cross B35 x Tx7000 in two locations over 2 years and compared it with earlier reports. Analysis using the combined stay green-rating means of seven environments and the expanded molecular map reconfirmed all four stay green QTLs (Stg1, Stg2, Stg3 and Stg4) that were identified earlier by Xu et al. (2000). Similarly, comparison of the stay green QTL locations with earlier reported results indicated that all four stay green QTLs showed consistency across different genetic backgrounds. Examination of the stay green QTL profiles of the best and poorest stay-green lines indicated that three stay green QTLs, Stg1, Stg2 and Stg3, appear to be important for the expression of this trait when the percent phenotypic variation, and the consistency in different backgrounds and different environments, are considered. A significant epistatic interaction involving Stg2 and a region on linkage group C was also identified for the stay green and chlorophyll content. We concluded that Stg2 is the most important QTL controlling stay green, explaining the maximum amount of phenotypic variation. This report further strengthens our view to target the Stg2 QTL region for gene discovery in order to improve the basic understanding of the stay green phenomenon, which might be helpful in manipulating this trait not only in sorghum but also in other cereal crop species., author dropping-particle , family P.K. Subudhi. D.T. Rosenow. H.T Nguyen, given , non-dropping-particle , parse-names false, suffix , container-title TAG Theoretical and Applied Genetics, id ITEM-1, issue August 2015, issued date-parts 2000 , page 733-741, title Quantitative trait loci for the stay green trait in sorghum ( Sorghum bicolor L. Moench) consistency across genetic backgrounds and environments, type article-journal, volume 101 , uris http//www.mendeley.com/documents/uuid4e66a521-69c9-444b-91a0-85a900983ab6 , mendeley formattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), manualFormatting Subudhi et al., 2000), plainTextFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000), previouslyFormattedCitation (P.K. Subudhi. D.T. Rosenow. H.T Nguyen, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json Subudhi et al., 2000). Direct and indirect selection approaches are widely used staygreen screening techniques. Direct approach uses environmental conditions in which the onset of stress factors is uniform and predictable whereas indirect uses well managed and stress environments ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5829/idosi.aejaes.2013.13.10.11045, author dropping-particle , family Moslem Abdipur, Hamid Reza Ramezani, given Vahid Bavei and Sajad Talaee, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 10, issued date-parts 2013 , page 1325-1338, title Effectiveness of Canopy Temperature and Chlorophyll Content Measurements at Different Plant Growth Stages for Screening of Drought Tolerant Wheat Genotype s, type article-journal, volume 13 , uris http//www.mendeley.com/documents/uuid1bf5db1d-b087-4559-8b47-798f8ca5f5cf , id ITEM-2, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-2, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013), manualFormatting (Abdipur et al., 2013 Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Moslem Abdipur, Hamid Reza Ramezani, 2013) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Abdipur et al., 2013 Beyene et al., 2015). Selection under both optimal and drought conditions represents the ideal screening approach for yield and yield stability ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1023/A1009673126345, ISBN 1380-3743, ISSN 13803743, abstract Drought is a serious agronomic problem and the single greatest factor contributing to crop yield loss in the world today. This problem may be alleviated by developing crops that are well adapted to dry-land environments. Sorghum (Sorghum bicolor (L.) Moench) is one of the most drought-tolerant grain crops and is an excellent crop model for evaluating mechanisms of drought tolerance. In this study, a set of 98 recombinant inbred (RI) sorghum lines was developed from a cross between two genotypes with contrasting drought reactions, TX7078 (pre-flowering-tolerant, post-flowering susceptible) and B35 (pre-flowering susceptible, post-flowering-tolerant). The RI population was characterized under drought and non-drought conditions for the inheritance of traits associated with post-flowering drought tolerance and for potentially related components of grain development. Quantitative trait loci (QTL) analysis identified 13 regions of the genome associated with one or more measures of post-flowering drought tolerance. Two QTL were identified with major effects on yield and staygreen under post-flowering drought. These loci were also associated with yield under fully irrigated conditions suggesting that these tolerance loci have pleiotropic effects on yield under non-drought conditions. Loci associated with rate and/or duration of grain development were also identified. QTL analysis indicated many loci that were associated with both rate and duration of grain development. High rate and short duration of grain development were generally associated with larger seed size, but only two of these loci were associated with differences in stability of performance under drought., author dropping-particle , family Mitchell R. Tuinstra1, Edwin M. Grote2, given Peter B. Goldsbrough1 Gebisa Ejeta2, non-dropping-particle , parse-names false, suffix , dropping-particle , family , given , non-dropping-particle , parse-names false, suffix , container-title Molecular Breeding, id ITEM-1, issued date-parts 1997 , page 439-448, title Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuid230720ce-0e29-43da-99cc-102a7b79dc5a , mendeley formattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), manualFormatting (Tuinstra et al., 1997), plainTextFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997), previouslyFormattedCitation (Mitchell R. Tuinstra1, Edwin M. Grote2 , 1997) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Tuinstra et al., 1997). To achieve this, both visual scoring of leaf and plant senescence and genomic tools such as marker assisted selection (MAS) can be used to select for ideal staygreen genotypes ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1186/1471-2164-15-909, ISBN 1471-2164, ISSN 14712164, PMID 25326366, abstract BACKGROUND Sorghum Sorghum bicolor (L.) Moench is an important dry-land cereal of the world providing food, fodder, feed and fuel. Stay-green (delayed-leaf senescence) is a key attribute in sorghum determining its adaptation to terminal drought stress. The objective of this study was to validate sorghum stay-green quantitative trait loci (QTL) identified in the past, and to identify new QTL in the genetic background of a post-rainy adapted genotype M35-1.nnRESULTS A genetic linkage map based on 245 F9 Recombinant Inbred Lines (RILs) derived from a cross between M35-1 (more senescent) and B35 (less senescent) with 237 markers consisting of 174 genomic, 60 genic and 3 morphological markers was used. The phenotypic data collected for three consecutive post-rainy crop seasons on the RIL population (M35-1 u00d7 B35) was used for QTL analysis. Sixty-one QTL were identified for various measures of stay-green trait and each trait was controlled by one to ten QTL. The phenotypic variation explained by each QTL ranged from 3.8 to 18.7. Co-localization of QTL for more than five traits was observed on two linkage groups i.e. on SBI-09-3 flanked by S18 and Xgap206 markers and, on SBI-03 flanked by XnhsbSFCILP67 and Xtxp31. QTL identified in this study were stable across environments and corresponded to sorghum stay-green and grain yield QTL reported previously. Of the 60 genic SSRs mapped, 14 were closely linked with QTL for ten traits. A genic marker, XnhsbSFCILP67 (Sb03g028240) encoding Indole-3-acetic acid-amido synthetase GH3.5, was co-located with QTL for GLB, GLM, PGLM and GLAM on SBI-03. Genes underlying key enzymes of chlorophyll metabolism were also found in the stay-green QTL regions.nnCONCLUSIONS We validated important stay-green QTL reported in the past in sorghum and detected new QTL influencing the stay-green related traits consistently. Stg2, Stg3 and StgB were prominent in their expression. Collectively, the QTL/markers identified are likely candidates for subsequent verification for their involvement in stay-green phenotype using NILs and to develop drought tolerant sorghum varieties through marker-assisted breeding for terminal drought tolerance in sorghum., author dropping-particle , family Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, given Seetharama Nadoor1 and Jagannatha Vishnu Patil, non-dropping-particle , parse-names false, suffix , container-title BMC Genomics, id ITEM-1, issue 1, issued date-parts 2014 , title Detection and validation of stay-green QTL in post-rainy sorghum involving widely adapted culti M35-1 and a popular stay-green genotype B35, type article-journal, volume 15 , uris http//www.mendeley.com/documents/uuid6b398253-a8ec-40b3-960b-6b154c4c4c70 , mendeley formattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014), manualFormatting (Reddy et al., 2014), plainTextFormattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014), previouslyFormattedCitation (Nagaraja Reddy Rama Reddy1, 2u2020, Madhusudhana Ragimasalawada1, Murali Mohan Sabbavarapu1u2020, 2014) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2014). Marker assisted selection (MAS) is more efficient, less time and resource consuming than conventional breeding approach ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), manualFormatting (Borrell et al., 2014), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014). Selection in either of the screening technique should always factor in yield and yield components to disprove of the concept that staygreen may be correlated with low yield attributed to low sink-source under post anthesis drought stress ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.1093/jxb/eru232, ISBN 1460-2431 (Electronic)r0022-0957 (Linking), ISSN 14602431, PMID 25381433, abstract Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice., author dropping-particle , family Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, given Patricia E. Klein5 and David R. Jordan1, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-1, issue 21, issued date-parts 2014 , page 6251-6263, title Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuidbb1b3b57-3ec4-4640-a08a-99a111573bbf , id ITEM-2, itemData DOI 10.1017/S1479262115000696, ISSN 1479263X, abstract Hybrid breeding relies on selection of genetically unrelated and complementary parents for key traits. The objective of this study was to examine genetic variation and identify unique sorghum genotypes using phenotypic and simple sequence repeat (SSR) markers and to determine their relationships with combining ability and heterosis for grain yield. A total of 32 landraces and four cytoplasmic male sterile (CMS) lines were phenotyped using 25 agro-morphological traits and genotyped with 30 polymorphic SSR markers. The landraces were crossed with four CMS lines using a line u00d7 tester mating design. The 128 hybrids, 36 parentals and four check varieties were field-evaluated using a 12 u00d7 14 alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield were determined. Genetic distance estimates ranged from 0.39 to 0.60 and 0.50 to 0.79, based on phenotypic and SSR markers, respectively. Landraces 72572, 75454, 200654, 239175, 239208, 244735A and 242039B and CMS lines ICSA 743 and ICSA 756 displayed positive and significant GCA effects for grain yield. Based on the SCA effects of yield, lines were classified into three heterotic groups aligned to the different cytoplasmic systems of testers. Lines with high GCA effects rendered hybrids with highly significant SCA effects with high mid-parent heterosis (MPH) for grain yield. Both marker systems were effective in demarcating sorghum genotypes that provided desirable cross-combinations with high combining ability effects and MPH for grain yield. The selected genotypes are recommended as potential parents for sorghum hybrid breeding in moisture stress environments., author dropping-particle , family Beyene Amelework, given Hussien Shimelis and Mark Laing, non-dropping-particle , parse-names false, suffix , dropping-particle , family African Center for Crop Improvement, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, given South Africa, non-dropping-particle , parse-names false, suffix , dropping-particle , family Received, given , non-dropping-particle , parse-names false, suffix , container-title Plant Genetic Resources Characterisation and Utilisation, id ITEM-2, issue 4, issued date-parts 2017 , page 335-347, title Genetic variation in sorghum as revealed by phenotypic and SSR markers Implications for combinng ability and heterosis for grain yield, type article-journal, volume 15 , uris http//www.mendeley.com/documents/uuid1396b5ac-7e1d-4f77-b191-777bcc46b356 , mendeley formattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework et al., 2017), manualFormatting (Borrell et al., 2014 Beyene et al., 2015 Amelework et al., 2017), plainTextFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework et al., 2017), previouslyFormattedCitation (Andrew K. Borrell1,, John E. Mullet2, Barbara George-Jaeggli3, Erik J. van Oosterom4, Graeme L. Hammer4, 2014a Beyene Amelework et al., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Borrell et al., 2014 Beyene et al., 2015 Amelework et al., 2017). Selection may also be done at plant growth phase at which they are more susceptible to waterstress ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-1, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007), manualFormatting (Reddy et al., 2007), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Reddy et al., 2007). Most breeding programs employ pedigree and recurrent selection methods to developed staygreen candidate populations ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid67183f5e-7608-499a-9e46-60588d02518f , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), manualFormatting (Beyene et al., 2015), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2015). Introgression of staygreen trait is easily achieved because of high heritability of staygreen loci presence in donor parents B35 and E-36-1ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, given , non-dropping-particle , parse-names false, suffix , container-title Theoretical and Applied Genetics, id ITEM-1, issue 8, issued date-parts 2000 , page 1225-1232, title Identification of genomic regions associated with stay-green in sorghum by testing RILs in multiple environments., type article-journal, volume 100 , uris http//www.mendeley.com/documents/uuid0c5c6955-bcee-4252-9de9-650b436cd859 , id ITEM-2, itemData author dropping-particle , family Belum VS Reddy, B Ramaiah, given A Ashok Kumar and P Sanjana Reddy International, non-dropping-particle , parse-names false, suffix , container-title International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) – Open Journal, id ITEM-2, issue 1, issued date-parts 2007 , page 4, title Evaluation of sorghum genotypes for the stay-green trait and g rain yield, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuida6caf3ef-d81a-4933-a4d1-a1398e553371 , id ITEM-3, itemData DOI 10.1093/jxb/eru037, ISBN 0022-0957, ISSN 14602431, PMID 24600017, abstract Stay-green (sometimes staygreen) refers to the heritable delayed foliar senescence character in model and crop plant species. In a cosmetic stay-green, a lesion interferes with an early step in chlorophyll catabolism. The possible contribution of synthesis to chlorophyll turnover in cosmetic stay-greens is considered. In functional stay-greens, the transition from the carbon capture period to the nitrogen mobilization (senescence) phase of canopy development is delayed, and/or the senescence syndrome proceeds slowly. Yield and composition in high-carbon (C) crops such as cereals, and in high-nitrogen (N) species such as legumes, reflect the source-sink relationship with canopy C capture and N remobilization. Quantitative trait loci studies show that functional stay-green is a valuable trait for improving crop stress tolerance, and is associated with the domestication syndrome in cereals. Stay-green variants reveal how autumnal senescence and dormancy are coordinated in trees. The stay-green phenotype can be the result of alterations in hormone metabolism and signalling, particularly affecting networks involving cytokinins and ethylene. Members of the WRKY and NAC families, and an ever-expanding cast of additional senescence-associated transcription factors, are identifiable by mutations that result in stay-green. Empirical selection for functional stay-green has contributed to increasing crop yields, particularly where it is part of a strategy that also targets other traits such as sink capacity and environmental sensitivity and is associated with appropriate crop management methodology. The onset and progress of senescence are phenological metrics that show climate change sensitivity, indicating that understanding stay-green can contribute to the design of appropriate crop types for future environments., author dropping-particle , family Thomas, given Howard, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ougham, given Helen, non-dropping-particle , parse-names false, suffix , container-title Journal of Experimental Botany, id ITEM-3, issue 14, issued date-parts 2014 , page 3889-3900, title The stay-green trait, type article-journal, volume 65 , uris http//www.mendeley.com/documents/uuid6204ec43-d0a6-4278-9b15-15dfb1db5f1d , mendeley formattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), manualFormatting ( Subudhi et al., 2000 Reddy et al., 2007 Thomas and Ougham, 2014), plainTextFormattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000), previouslyFormattedCitation (Belum VS Reddy, B Ramaiah, 2007 Thomas Ougham, 2014b Y.Z. Tao u00b7 R.G. Henzell u00b7 D.R. Jordan u00b7 D.G. Butler A.M. Kelly u00b7 C.L. McIntyre, 2000) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json ( Subudhi et al., 2000 Reddy et al., 2007 Thomas and Ougham, 2014). Selection criteria for staygreen genotypes are best executed under controlled and drought-stress environments because of the polygenic nature of trait and high influence of genotype x environment interaction ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5897/AJAR2015.9595, ISSN 1991-637X, abstract Sorghum is grown in semi-arid to arid regions of the world and serves as the staple food for about half a billion people in sub-Saharan Africa and Asia. The adaptation of grain sorghum to a wide range of environmental conditions has led to the evolution and existence of extensive genetic variation for drought tolerance. Consequently, sorghum is expected to play an increasingly important role in agriculture and meeting world food demand in the face of climate change, land degradation and increasing water scarcity. Drought is a complex phenomenon, and is considered one of the most significant factors limiting crop yields around the world and continues to be a challenge to plant breeders, despite many decades of research. Underestimating the genetics and the physiological mechanisms underlying drought tolerance is vital for the breeding to alleviate adverse effects of drought in order to boost productivity. In this literature review, research findings from the 1970s up to present are included. Most of the basic researches on the mechanism of drought tolerance were done in the early 1980s, and most of the current researches focus on verification and fine-tuning of methodologies. The paper outlines the main effects of drought on crop growth and development, and yield. It then examines the basic information on physiological mechanisms of drought in crops. Subsequent discussion is given on the genetic control of drought tolerance, and breeding methods in sorghum., author dropping-particle , family Beyene Amelework1, Hussien Shimelis1, given Pangirayi Tongoona2 and Mark Laing1, non-dropping-particle , parse-names false, suffix , dropping-particle , family 1African, given , non-dropping-particle , parse-names false, suffix , container-title African Journal of Agricultural Research, id ITEM-1, issue 31, issued date-parts 2015 , page 3029-3040, title Physiological mechanisms of drought tolerance in sorghum, genetic basis and breeding methods A review, type article-journal, volume 10 , uris http//www.mendeley.com/documents/uuid208da58c-8416-4334-ab96-0b24bfd33685 , id ITEM-2, itemData author dropping-particle , family Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., given Subhash Bharani and Vinayak Turaidar, non-dropping-particle , parse-names false, suffix , container-title Int. J. Pure App. Biosci., id ITEM-2, issue 4, issued date-parts 2017 , page 221-237, title Mechanisms of Drought Tolerance in Sorghum A Review, type article-journal, volume 5 , uris http//www.mendeley.com/documents/uuid69473559-95d1-411c-87d6-aa2627b99dc0 , mendeley formattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), manualFormatting (Beyene et al., 2017), plainTextFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017), previouslyFormattedCitation (Beyene Amelework1, Hussien Shimelis1 1African, 2015a Krupa, K. N., Ningaraj Dalawai, Shashidhar, H. E., Harinikumar, K. M., Manojkumar, H. B., 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Beyene et al., 2017). Genetic information on combining ability of parental lines and crosses on one hand is important in making choices of the right breeding procedure, method of selection and superior parental lines ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family George, given Acquaah, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 2012 , number-of-pages 291-293, title Breeding for resistance to abiotic stresses, type book , uris http//www.mendeley.com/documents/uuiddb6fb1e0-b646-4012-9eb7-6857d6264aa6 , mendeley formattedCitation (George, 2012), manualFormatting (Acquaah et al, 2012), plainTextFormattedCitation (George, 2012), previouslyFormattedCitation (George, 2012) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Acquaah et al, 2012). Full diallel design on the other hand provides efficient assessment of potent parents, estimation of additive and dominance genetic effects, genetic gain from both additive and non-additive genetic variances, effects of reciprocal, subsequent partitioning of reciprocal into maternal and nonmaterial effects and the gene action controlling them ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.15406/bbij.2016.04.00085, author dropping-particle , family Parviz, Fasahat. Abazar, Rajabi. Javad, given Mohsent. John Derera., non-dropping-particle , parse-names false, suffix , container-title Biometrics and Biostatistics International Journal, id ITEM-1, issue 1, issued date-parts 2016 , page 1-24, title Principles and Utilization of Combining Ability in Plant, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuiddeb9b5a8-a474-4e3e-96ed-d46d6332a5ae , mendeley formattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), manualFormatting (Fasahat et al., 2016), plainTextFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016), previouslyFormattedCitation (Parviz, Fasahat. Abazar, Rajabi. Javad, 2016) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Fasahat et al., 2016). Partitioning of genetic effects into general and specific combining ability generates powerful information about the roles of each parent when it is used as male and male ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/eajsci.v4i1.71522, author dropping-particle , family Girma, given M, non-dropping-particle , parse-names false, suffix , dropping-particle , family Amsalu, given a, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ketema, given B, non-dropping-particle , parse-names false, suffix , container-title East African Journal of Sciences, id ITEM-1, issued date-parts 2011 , page 34-40, title Combining Ability for Yield and its Components in Ethiopian Sorghum (iSorghum bicolor/i (L.) Moench) Landraces, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuidbbd231eb-71cf-45a6-990e-fe8fcc20b776 , mendeley formattedCitation (Girma, Amsalu, Ketema, 2011), manualFormatting (Girma et al., 2011), plainTextFormattedCitation (Girma, Amsalu, Ketema, 2011), previouslyFormattedCitation (Girma, Amsalu, Ketema, 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Girma et al., 2011). The success in generating good combiners relies much on broader and diverse genetic background the breeder hybridizes and the choice of powerful mating design which aims to give inference of various gene effects underpinning the trait of interest ADDIN CSL_CITATION citationItems id ITEM-1, itemData author dropping-particle , family Kumar, given A Ashok, non-dropping-particle , parse-names false, suffix , id ITEM-1, issued date-parts 1985 , page 93-104, title Population improvement in sorghum, type article-journal , uris http//www.mendeley.com/documents/uuid8de7daa4-0295-4fb3-a6d1-da252fbc2ba1 , mendeley formattedCitation (Kumar, 1985), plainTextFormattedCitation (Kumar, 1985), previouslyFormattedCitation (Kumar, 1985) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Kumar, 1985). Thus, this study aims to select good combiners for earliness and yield under drought stress condition to develop superior sorghum hybrids for improved food and nutritional security in drought prone areas of South Sudan. 4.2 Materials and methods 4.2.1 Site description The site descriptions remain as described in section 3.2.1. 4.2.2 Germplasm The genetic materials used in this study involved three farmer preferred landraces (Akuorachot, Okabir and Lodoka) from South Sudan collection and three staygreen donor parents (B35, ICSV111IN and Macia) obtained from ICRISAT- Nairobi (Table 4.1). Table 4.1. Parental lines intercrossed in a 6 x 6 full diallel mating designLodokaICSV111INB35OkabirAkuorachotMaciaLodokaICSV111INB25OkabirAkuorachotMacia 4.2.3 Experimental design The 36 crosses and parents obtained from a 6 x 6 full diallel mating design were laid down in a randomized complete block design with two replications. Replicates were spaced at 1.5 m, inter row and intra spacing was 70cm and 20 cm respectively. The experiment was well irrigated from sowing to anthesis stage where irrigation was withheld. 4.2.4 Data collection The data collected included Days to 50 flowering was collected when 50 percent of the true F1s plant had flowered Panicle weight (g) was recorded by weighing the panicle of true F1s in a plot Grain weight (g) Was recorded by weighing total grain weight of true F1s per plot 100seedweight Was recorded by weighing 100seed of true F1 per plot 4.2.5 Data analysis Data collected over one season were subjected to SAS statistical software using GLM procedures based on Griffing method I for full diallel. The fixed model was used to separate GCA and SCA and reciprocal effects. Replication and block effects were random and the rest were considered as fixed variables. 4.2.5.1 Griffing Method I, Model I (Fixed Model). To partition the GCA and SCA effect, Griffing Method I, Model I or fixed model was used as performed by SAS version 9.4 with general linear model (GLM) proeedure. eijkl is the experimental error due to environmental effect associated with the ijklth which is assumed to be uncorrelated and normally distributed with zero mean and variance VE. b Number of replicates cNumber of plants 4.3 Results 4.3.1 Analysis of variance for the different traits among the sorghum genotypes The mean square for the various traits showed no significant differences among the genotypes, reciprocal, maternal and non maternal effects except days to flowering (Table 4.1). Table 4.1 Means square for all the traits studied under drought stress conditionsSource of variation DFDFPWTGWTHSWREP130.680556ns377.66681ns722ns2.13555556nsGenotypes35171.680556417.42757ns287.66241ns0.53136508nsGCA5724.061ns394.745ns108.623ns0.38261SCA1578.868ns374.911ns198.186ns0.87631nsREC1580.367467.505ns436.819ns0.236nsMAT5115.333607.622ns425.809ns0.24417nsNMAT1062.883397.447ns442.323ns0.23192nsError3515.309127436.10686414.869710.4195556Total71DF days to flowering, PWT panicle weight, GWT grain weight and HSW 100-seed weight, GCA general combining ability, MAT maternal effect. NMAT nonmaterial effect ns not significance, . significant at P0.05 and significant at P0.01. 4.3.2 Mean performance of the single cross sorghum hybrids The earliness trait was exhibited by the crosses Macia x ICSV111IN, ICSV111IN x Macia, ICSV111IN x ICSV111IN, B35 x ICSV111IN, Macia x Okabir, B35 x Macia and B35 x Akuorachot. The lateness trait was evident among the crosses Okabir x Akuorachot, Lodoka x Lodoka, Lodoka x Okabir, Akuorachot x Okabir, Okabir x Okabir, Okabir x Macia, Lodoka x B35, Maica x B35, Okabir x B35, Macia x Lodoka, Akuorachot x B35, Lodoka x Akuorachot. The highest panicle weight were recorded for F1 generation between crosses Okabir x Macia, ICSV111IN x Lodoka, Macia x Macia, B35 x Lodoka, Okabir x Okabir, Lodoka x ICSV111IN, Akuorachot x Lodoka, ICSV111IN x Okabir, B35 x Macia, B35 x ICSV111IN, Macia x ICSV111IN, Akuorachot x B35, and Macia x Akuorachot. The highest 100-seed weight was recorded among the crosses B35 x ICSV111IN, ICSV111IN x B35, Macia x Macia, Macia x ICSV111IN, Lodoka x ICSV111IN, Lodoka x Akuorachot, Okabir x ICSV111IN, Macia x B35, Macia x Lodoka, Macia x Akuorachot, Okabir x Lodoka, Lodoka x ICSV111IN, Lodoka x Lodoka, Akuorachot x Lodoka, Okabir x Macia and ICSV111IN x Lodoka (Table 4.2). Table 4.2 Means performance of F1 crosses between South Sudan farmers preferred lines and exotic linesGenotypesDFPWTGWTHSMLodoka x Lodoka8642.834.23.2Lodoka x ICSV111IN6866.7543.653.6Lodoka x B357533.725.553.2Lodoka x Okabir8259.4513.05Lodoka Akuorachot7238.6530.253.45Lodoka x Macia645540.12.5ICSV111IN x Lodoka6481.4566.553.1ICSV111IN x ICSV111IN5545.1535.852.25ICSV111IN x B3555.552.441.654.1ICSV111IN x Okabir676551.452.65ICSV111IN xAkuorachot57.551.1539.552.95ICSV111IN x Macia55.553.640.652.65B35 x Lodoka62.579.249.852.35B35 x ICSV111IN55.561.347.94.15B35 x B3561.544.430.451.85B35 x Okabir6552.1539.92.9B35 x Akuorachot6566.553.252.5B35 x Macia5762.1545.92.95Okabir x Lodoka71.55647.353.25Okabir x ICSV111IN7025.118.053.4Okabir x B357344.933.652.6Okabir x Okabir7871.1546.552.4Okabir x Akuorachot9344.1533.62.5Okabir x Macia7693.0576.93.15Okabir x Lodoka7165.356.153.15Akuorachot x ICSV111IN5838.2533.553.7Akuorachot xB357259.6547.92.85Akourachot x Okabir7951.742.52.5Akuorachot x Akuorachot61.540.8530.62.95Akuorachot x Macia6541.7527.752.95Macia x Lodoka72.553.843.33.35Macia x B3554.559.8544.42.4Macia xB3573.545.2532.93.35Macia x Okabir605623.252.9Macia x Akuorachot66.559.446.33.25Macia x Macia70.581.0558.83.75Mean67.597255.498641.97782.99444CV5.7882445.593448.521821.6311DF days to 50flowering. PWT panicle weight, GWT grain weigh and HSW 100-seed weight, 1Lodoka, 2 ICSV111IN, 3 B35, 4 Okabir, 5 Akuorachot and 6 Macia. 4.3.3 General combining ability estimates among the sorghum genotypes For the days to flowering, the parents ICSV111IN, B35 and Macia had negative GCA effects implying earliness. The best general combiners for panicle weight were Macia and Lodoka with positive GCA effects. The parent Lodoka showed the highest GCA for grain weight. With regard to 100 seed mass, only Lodoka, Macia and ICSV111IN showed positive GCA effects (Table 4.3). Table 4.3 Estimate of GCA among sorghum genotypesGenotypesDFPWTGWTHSMLodoka5.281.534.310.12ICSV111IN-7.97-0.392.390.11B35-2.85-2.03-3.42-0.11Okabir6.780.58-0.80-0.19Akuorachot 0.90-2.64-4.03-0.02Macia-2.142.941.550.08Key. DOF days to flowering, PWTpanicle weight, GWT grain weight, HSW 100seedmass. 1Lodoka, 2 ICSV111IN, 3 B35, 4 Okabir, 5 Akuorachot and 6 Macia 4.3.4 Specific combining ability effects among the sorghum hybrids With regard to earliness, Lodoka X Macia had the highest SCA effect for days to flowering while Okabir X Akuorachot was the latest. The hybrid B35 X Akuorachot had the highest SCA value for panicle weight while Macia X Macia had the lowest SCA effect for panicle weight. Lodoka X ICSV111IN showed the highest SCA effect for grain weight while Macia X Macia had the lowest SCA. Macia X Macia had the lowest 100 seed mass with the lowest SCA value. Table 4.4 Estimate of SCA among the sorghum hybridsGenotypesDFPWTGWTHSMLodoka X Lodoka 7.85-10.85-17.79-0.04Lodoka X ICSV111IN1.1011.9730.030.13Lodoka X B35-1.28-3.78-6.56-0.23Lodoka X Okabir -2.905.082.300.22Lodoka X Akuorachot -2.282.33-0.450.20Lodoka X Macia -10.336.0910.26-0.24ICSV111 X ICSV111IN3.35-5.36-12.30-0.96ICSV111IN X B35-1.285.222.441.13ICSV111IN X Okabir 2.10-7.43-10.200.11ICSV111IN X Akuorachot -2.78-2.40-5.180.24ICSV111IN X Macia -5.833.357.510.30B35 X B35-0.40-7.46-6.08-0.93B35 X Okabir -2.53-3.76-2.370.05B35 X Akuorachot 2.8514.9814.66-0.19B35 X Macia 3.043.983.981.11Okabir X Okabir -3.153.404.79-0.22Okabir X Akuorachot 10.72-1.87-0.48-0.29Okabir X Macia -1.081.171.170.35Akuorachot X Akuorachot -7.90-6.09-4.70-0.01Akuorachot X Macia 7.290.840.840.05Macia X Macia 6.92-7.59-23.75-1.57DOF days to flowering, PWTpanicle weight, GWT grain weight, HSW 100seedmass. 1Lodoka, 2 ICSV111IN, 3 B35, 4 Okabir, 5 Akuorachot and 6 Macia The RCA effects for the days to flowering were highest on the cross B35 X Macia implying earliness. For the panicle weight, Okabir X Macia had the highest RCA effects. Table 4.5 Estimate of reciprocal combining ability (RCA) effects among sorghum genotypesGenotypesDFPWTGWTHSMLodoka X ICSV111IN2.0-11.513.60.3Lodoka X B356.3-12.2-12.20.4Lodoka X Okabir 5.31.81.8-0.1Lodoka X Akuorachot 0.5-13.0-13.00.2Lodoka X Macia -4.3-1.6-1.6-0.4ICSV111IN X B350.0-3.1-3.10.0ICSV111IN X Okabir -1.516.716.7-0.4ICSV111IN X Akuorachot -0.33.03.0-0.4ICSV111IN X Macia 0.5-1.9-1.90.1B35 X Okabir -4.03.13.10.2B35 X Akuorachot -3.52.72.7-0.2B35 X Macia-8.36.56.5-0.2Okabir X Akuorachot 7.0-4.5-4.50.0Okabir X Macia8.026.826.80.1Akuorachot x Macia-0.8-9.3-9.3-0.2DOF days to flowering, PWTpanicle weight, GWT grain weight, HSW 100seedmass. 1Lodoka, 2 ICSV111IN, 3 B35, 4 Okabir, 5 Akuorachot and 6 Macia 4.4 Discussions 4.4.1 General combining ability estimates among the sorghum genotypes The parents, hybrids and their reciprocals showed significant differences for days to flowering suggesting their diversity with regard to maturity. There were significant differences among the maternal and non-maternal effects implying that cytoplasmic genes play a great role in regulating maturity. There were larger mean squares of GCA than the SCA for days to flowering and panicle weight showing that additive genes play a bigger role than non additive genes in control of such traits. The absence of significance among the general and specific combining ability effects on panicle weight, grain weight and 100-seed weight could be attributed to the effect of epistatic genes. Negative significant general combining ability effects (GCA) were noted for days to flowering for parents ICSV111IN, B35 and Macia suggests that these parents had the earliness trait. Previous research have reported negative GCA effects for days to maturity ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/eajsci.v4i1.71522, author dropping-particle , family Girma, given M, non-dropping-particle , parse-names false, suffix , dropping-particle , family Amsalu, given a, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ketema, given B, non-dropping-particle , parse-names false, suffix , container-title East African Journal of Sciences, id ITEM-1, issued date-parts 2011 , page 34-40, title Combining Ability for Yield and its Components in Ethiopian Sorghum (iSorghum bicolor/i (L.) Moench) Landraces, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuidbbd231eb-71cf-45a6-990e-fe8fcc20b776 , id ITEM-2, itemData DOI 10.5539/jas.v9n2p122, author dropping-particle , family Sally Chikuta1, 2, Thomas Odong1, given Fred Kabi1 Patrick Rubaihayo1 1, non-dropping-particle , parse-names false, suffix , id ITEM-2, issue 2, issued date-parts 2017 , page 122-130, title Combining Ability and Heterosis of Selected Grain and Forage Dual Purpose Sorghum Genotypes, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuidef5ccb50-fbe9-4963-b276-c8e9f52e1504 , mendeley formattedCitation (Girma et al., 2011 Sally Chikuta1, 2, Thomas Odong1, 2017), manualFormatting (Girma et al., 2011 Sally et al., 2017), plainTextFormattedCitation (Girma et al., 2011 Sally Chikuta1, 2, Thomas Odong1, 2017), previouslyFormattedCitation (Girma et al., 2011 Sally Chikuta1, 2, Thomas Odong1, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Girma et al., 2011 Sally et al., 2017). The parents Lodoka, Okabir and Akuorachot with positive days to flowering implied lateness thus conferring the late physiological maturity. With regard to the panicle weight, the parental lines Macia, Okabir and Lodoka recorded positive GCA and high mean values for panicle weight. These parental lines are superior combiners for panicle weight. In selection for superior parents with good plant height and panicle weight, ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/eajsci.v4i1.71522, author dropping-particle , family Girma, given M, non-dropping-particle , parse-names false, suffix , dropping-particle , family Amsalu, given a, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ketema, given B, non-dropping-particle , parse-names false, suffix , container-title East African Journal of Sciences, id ITEM-1, issued date-parts 2011 , page 34-40, title Combining Ability for Yield and its Components in Ethiopian Sorghum (iSorghum bicolor/i (L.) Moench) Landraces, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuidbbd231eb-71cf-45a6-990e-fe8fcc20b776 , mendeley formattedCitation (Girma et al., 2011), plainTextFormattedCitation (Girma et al., 2011), previouslyFormattedCitation (Girma et al., 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Girma et al., 2011) identified parents with positive GCA for the interest traits. With regard to the combining ability for grain yield, the parents Macia, Lodoka, and ICSV111IN showed positive GCA effects implying they are good combiners for grain yield compared to parental lines B35, Okabir and Akuorachot which showed inferiority with regards to grain weight. For the 100-Seedweight, the parent Macia, Lodoka and ICSV111IN showed positive GCA suggesting that they are good combiners for that trait. The high GCA effects are governed by genes with additive effects ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5539/jas.v9n2p122, author dropping-particle , family Sally Chikuta1, 2, Thomas Odong1, given Fred Kabi1 Patrick Rubaihayo1 1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2017 , page 122-130, title Combining Ability and Heterosis of Selected Grain and Forage Dual Purpose Sorghum Genotypes, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuidef5ccb50-fbe9-4963-b276-c8e9f52e1504 , mendeley formattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), manualFormatting (Sally and Odongi, 2017), plainTextFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), previouslyFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sally and Odongi, 2017). 4.4.2 Estimates of specific combining ability effects among the sorghum hybrids The measure of deviation of a cross from the average performance of the parental genotypes is defined as specific combining ability ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5539/jas.v9n2p122, author dropping-particle , family Sally Chikuta1, 2, Thomas Odong1, given Fred Kabi1 Patrick Rubaihayo1 1, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2017 , page 122-130, title Combining Ability and Heterosis of Selected Grain and Forage Dual Purpose Sorghum Genotypes, type article-journal, volume 9 , uris http//www.mendeley.com/documents/uuidef5ccb50-fbe9-4963-b276-c8e9f52e1504 , mendeley formattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), manualFormatting (Sally and Odongi, 2017), plainTextFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017), previouslyFormattedCitation (Sally Chikuta1, 2, Thomas Odong1, 2017) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Sally and Odongi, 2017). Crosses that gave positive significant SCA for days to maturity induce lateness ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/eajsci.v4i1.71522, author dropping-particle , family Girma, given M, non-dropping-particle , parse-names false, suffix , dropping-particle , family Amsalu, given a, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ketema, given B, non-dropping-particle , parse-names false, suffix , container-title East African Journal of Sciences, id ITEM-1, issued date-parts 2011 , page 34-40, title Combining Ability for Yield and its Components in Ethiopian Sorghum (iSorghum bicolor/i (L.) Moench) Landraces, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuidbbd231eb-71cf-45a6-990e-fe8fcc20b776 , mendeley formattedCitation (Girma et al., 2011), manualFormatting (Girma et al., 2011), plainTextFormattedCitation (Girma et al., 2011), previouslyFormattedCitation (Girma et al., 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Girma et al., 2011). Significant negative specific combining ability for days to flowering was exhibited by F1 cross, Okabir x Macia. However, crosses that showed significant and negative SCA effect expressed earliness ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.4314/eajsci.v4i1.71522, author dropping-particle , family Girma, given M, non-dropping-particle , parse-names false, suffix , dropping-particle , family Amsalu, given a, non-dropping-particle , parse-names false, suffix , dropping-particle , family Ketema, given B, non-dropping-particle , parse-names false, suffix , container-title East African Journal of Sciences, id ITEM-1, issued date-parts 2011 , page 34-40, title Combining Ability for Yield and its Components in Ethiopian Sorghum (iSorghum bicolor/i (L.) Moench) Landraces, type article-journal, volume 4 , uris http//www.mendeley.com/documents/uuidbbd231eb-71cf-45a6-990e-fe8fcc20b776 , mendeley formattedCitation (Girma et al., 2011), manualFormatting (Girma et al., 2011), plainTextFormattedCitation (Girma et al., 2011), previouslyFormattedCitation (Girma et al., 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Girma et al., 2011). Thus, the negative significant SCA in this study might be due to additive gene effect in parent Macia overriding non-additive genetic action in late parental Okabir. In three out 15 F1 generation crosses, significant positive specific combining ability (SCA) effect for 100-seedweight was revealed in parent ICSV111IN x ICSV111IN, B35 x B35 and ICSV111IN x B35 suggesting that these crosses are superior combiners for 100 seed weight. 4.4.3 Reciprocal combining effects among the sorghum hybrids The Reciprocal effects were partitioned into maternal and non-maternal effects. Positive maternal effect for days to flowering was reported among the parents Lodoka, Macia and the cross Lodoka x Okabir. ADDIN CSL_CITATION citationItems id ITEM-1, itemData DOI 10.5539/jas.v3n2p213, author dropping-particle , family Mahgoub, given Galal M A, non-dropping-particle , parse-names false, suffix , id ITEM-1, issue 2, issued date-parts 2011 , page 213-222, title Partitioning of General and Specific Combining Ability Effects for Estimating Maternal and Reciprocal Effects, type article-journal, volume 3 , uris http//www.mendeley.com/documents/uuidbdda6ba8-c55b-4769-aebb-c6b1c05f5aeb , mendeley formattedCitation (Mahgoub, 2011), plainTextFormattedCitation (Mahgoub, 2011), previouslyFormattedCitation (Mahgoub, 2011) , properties , schema https//github.com/citation-style-language/schema/raw/master/csl-citation.json (Mahgoub, 2011) reported significant and positive maternal effect in his study which he associated with the contribution of nuclear genes which induce lateness. CHAPTER FIVE GENERAL DISCUSSION, CONCLUSION AND RECOMMENDATION 5.1 GENERAL DISCUSSION AND CONCLUSION The aim of this study was to identify drought tolerant, early maturing and high yielding sorghum genotypes for drought prone agro-ecological zones and also to establish the combining ability for earliness, drought and yield related components among an assortment of sorghum genotypes assembled from diverse origins. Genotypes and water regimes had effects on staygreen score, dry leaf scores, waxy bloom, leaf area, leaf rolling, total leaf count and lodging implying genetic diversity for the sorghum genotypes evaluated in this study. The correlation coefficient revealed that staygreen was positively correlated with panicle weight, grain yield, 100-seed weight and harvesting index suggesting that these traits could be used to select for drought tolerant sorghum genotypes. The sorghum genotypes Olerere (12.82) exhibiting the lowest DLS while Omuhathi (76.23) showed the highest senescence. Reduced total leaf counts and net leaf area were observed among improved staygreen lines namely IESV92028DL IESV91111DL, Mahube, IESV92172DL, Gwada and IESV23010DL. The sorghum genotypes with staygreen traits minimize water use during the pre-anthesis phase so as to conserve water for grain filling during the grain development phase leading to high yields. The accessions that scored dense wax load under drought stress condition were Gwada, ICSR161, Mahube, AG8, IESV91131DL, IESV91111DL, IESV92028DL and IESV92172DL and comprised of lines drawn from ICRISAT- Nairobi gene bank. Dense wax load under drought stress condition has been associated with cuticular wax biosynthesis translocation, composition and density and are influenced solely by environmental factors including solar radiation, temperature, moisture, and humidity in sorghum. The superior lines that outperformed the check variety for earliness were Wotecollection1 (56.94days), IESV23010DL (58.06days, ZSV3 (60.09days), Bizany (61.17days) and Tabat (61.17days). However, there were yield penalties observed among the accessions wotecollection1, Bizany, ZSV3 and Tabat. Thus, the accessions IESV23010DL would best serve as an ideal drought evading candidate with better performance for grain yield. The genotypes Lobuheti (50.65g), IESV91131DL (46.52g), Lodoka1 (47.08g) and IESV92172DL (46.69g) showed superior field weights as opposed to the check variety. Among yield contributing components, harvesting index and threshability are considered key determinants of the final grain yield. Accession IESV91131DL and IESV92172DL recorded high harvesting index (3.13 and 6.86) and threshing percentage of 73.94 and 67.34. Results of correlation coefficient revealed that panicle weight showed positive correlation with grain yield, harvesting index, and panicle width suggesting that these traits could be used as the basis for selection for high grain yield in sorghum breeding programs. There were significant differences among the maternal and non-maternal effects implying that cytoplasmic genes play a great role in regulating maturity. There were larger mean squares of GCA than the SCA for days to flowering and panicle weight showing that additive genes play a bigger role than non additive genes in control of such traits. Negative significant general combining ability effects (GCA) were noted for days to flowering for parents ICSV111IN, B35 and Macia suggests that these parents had the earliness trait. The parents Lodoka, Okabir and Akuorachot with positive days to flowering implied lateness thus conferring the late physiological maturity. With regard to the panicle weight, the parental lines Macia, Okabir and Lodoka recorded positive GCA and high mean values for panicle weight. These parental lines are superior combiners for panicle weight. With regard to the combining ability for grain yield, the parents Macia, Lodoka, and ICSV111IN showed positive GCA effects implying they are good combiners for grain yield compared to parental lines B35, Okabir and Akuorachot which showed inferiority with regards to grain weight. For the 100-Seedweight, the parent Macia, Lodoka and ICSV111IN showed positive GCA suggesting that they are good combiners for that trait. Significant negative specific combining ability for days to flowering was exhibited by F1 cross, Okabir x Macia. In three out 15 F1 generation crosses, significant positive specific combining ability (SCA) effect for 100-seedweight was revealed in parent ICSV111IN x ICSV111IN, B35 x B35 and ICSV111IN x B35 suggesting that these crosses are superior combiners for 100 seed weight. Positive maternal effect for days to flowering was reported among the parents Lodoka, Macia and the cross Lodoka x Okabir. 5.2 RECOMMENDATIONS The superior sorghum parents identified should be screened across more diverse environments to validate the results The superior parents could also be used to develop superior drought tolerant hybrids for release to the drought prone areas of south Sudan. REFERENCES A, Bibi, H, A., Sadaqat, M, H, N Tahir., and H, M, Abram. 2012, Screening of sorghum (Sorghum bicolor L. Moench) for drought tolerance at seedling stage in polyethylene glycol. The Journal of Animal and Plant Science, 22(3), 2-8. 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