Drought and High Temperature Stress in Sorghum: Physiological, Genetic, and Molecular Insights and Breeding Approaches

Sorghum is one of the staple crops for millions of people in Sub-Saharan Africa (SSA) and South Asia (SA). The future climate in these sorghum production regions is likely to have unexpected short or long episodes of drought and/or high temperature (HT), which can cause significant yield losses. Therefore, to achieve food and nutritional security, drought and HT stress tolerance ability in sorghum must be genetically improved. Drought tolerance mechanism, stay green, and grain yield under stress has been widely studied. However, novel traits associated with drought (restricted transpiration and root architecture) need to be explored and utilized in breeding. In sorghum, knowledge on the traits associated with HT tolerance is limited. Heat shock transcription factors, dehydrins, and genes associated with hormones such as auxin, ethylene, and abscisic acid and compatible solutes are involved in drought stress modulation. In contrast, our understanding of HT tolerance at the omic level is limited and needs attention. Breeding programs have exploited limited traits with narrow genetic and genomic resources to develop drought or heat tolerant lines. Reproductive stages of sorghum are relatively more sensitive to stress compared to vegetative stages. Therefore, breeding should incorporate appropriate pre-flowering and post-flowering tolerance in a broad genetic base population and in heterotic hybrid breeding pipelines. Currently, more than 240 QTLs are reported for drought tolerance-associated traits in sorghum prospecting discovery of trait markers. Identifying traits and better understanding of physiological and genetic mechanisms and quantification of genetic variability for these traits may enhance HT tolerance. Drought and HT tolerance can be improved by better understanding mechanisms associated with tolerance and screening large germplasm collections to identify tolerant lines and incorporation of those traits into elite breeding lines. Systems approaches help in identifying the best donors of tolerance to be incorporated in the SSA and SA sorghum breeding programs. Integrated breeding with use of high-throughput precision phenomics and genomics can deliver a range of drought and HT tolerant genotypes that can improve yield and resilience of sorghum under drought and HT stresses.

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Evaluation of cowpea (Vigna unguiculata (L.) Walp.) germplasm lines for tolerance to drought

Plant Genetic Resources ◽

10.1017/s1479262112000214 ◽

2012 ◽

Vol 10 (3) ◽

pp. 171-176 ◽

Cited By ~ 16

Author(s):

Christian A. Fatokun ◽

Ousmane Boukar ◽

Satoru Muranaka

Keyword(s):

Drought Tolerance ◽

Sub Saharan Africa ◽

Grain Legume ◽

International Institute ◽

Breeding Lines ◽

Germplasm Collections ◽

Legume Crop ◽

Drought Tolerant ◽

Cowpea Varieties ◽

Sub Saharan

Cowpea is an important grain legume crop in sub-Saharan Africa (SSA) where, on a worldwide basis, the bulk is produced and consumed. The dry savanna area of SSA is where cowpea is mostly grown under rain-fed conditions. The crop is therefore prone to drought which may occur early, mid and/or late in the cropping season. Compared with many other crops, cowpea is drought tolerant, even though drought is still a major constraint limiting its productivity in SSA. Increasing the level of drought tolerance in existing cowpea varieties grown by farmers would enable them to obtain more and stable yield from their cowpea fields. As a first step towards enhancing drought tolerance in existing cowpea varieties, 1288 lines were selected randomly from cowpea germplasm collections maintained at the International Institute of Tropical Agriculture, and evaluated for their drought tolerance at Ibadan. Drought was imposed by withdrawal of irrigation from 5 weeks after sowing. On average, drought reduced the number of days to flower by 12 d, and the mean grain yield per plant was also reduced by 67.28%. A few of the cowpea lines stayed green for up to 6 weeks after irrigation was stopped, even though some of these produced no pods when the study was terminated. Further evaluation in the screenhouse of 142 selected drought-tolerant lines helped to identify six lines that could be potential parents for developing breeding lines with enhanced drought tolerance.

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(1) Genetic Diversity of Cowpea [Vigna unguiculata (L.) Walp.] Breeding Lines from Different Countries Determined by AFLP Markers

HortScience ◽

10.21273/hortsci.40.4.998a ◽

2005 ◽

Vol 40 (4) ◽

pp. 998A-998 ◽

Cited By ~ 1

Author(s):

Jinggui Fang ◽

Panchanoor S. Devanand ◽

Chih Cheng T. Chao ◽

Philip A. Roberts ◽

Jeff D. Ehlers

Keyword(s):

Genetic Diversity ◽

South America ◽

Near Infrared ◽

Genetic Relationships ◽

The United States ◽

Aflp Markers ◽

Sub Saharan Africa ◽

Breeding Programs ◽

Breeding Lines

Cowpea (2n=2x=22) is a high protein, short-cycle, and essential legume food crop of the tropics, especially in the low input agricultural areas of sub-Saharan Africa, Asia, and South America. Lack of genetic diversity within breeding programs can limit long-term gains from selection. The cowpea gene pool is thought to be narrow and the genetic diversity within breeding programs could be even less diverse. Genetic relationships among 87 cowpea accessions, including 60 advanced breeding lines from six breeding programs in Africa and the United States, and 27 accessions from Africa, Asia, and South America were examined using amplified fragment length polymorphism (AFLP) markers with six near-infrared fluorescence labeled EcoR I + 3/Mse I + 3 primer sets. A total of 382 bands were scored among the accessions with 207 polymorphic bands (54.2%). Overall, the 87 cowpea accessions have narrow genetic basis and they shared minimum 86% genetic similarities. The data also show that the advanced breeding lines of different programs have higher genetic affinities with lines from the same program but not with lines from other programs. The results suggest that there is a need to incorporate additional germplasm of different genetic background into these breeding lines and to ensure the long-term genetic gains of the programs.

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Screening the USDA Watermelon Germplasm Collection for Drought Tolerance at the Seedling Stage

HortScience ◽

10.21273/hortsci.46.9.1245 ◽

2011 ◽

Vol 46 (9) ◽

pp. 1245-1248 ◽

Cited By ~ 19

Author(s):

Haiying Zhang ◽

Guoyi Gong ◽

Shaogui Guo ◽

Yi Ren ◽

Yong Xu ◽

...

Keyword(s):

Drought Tolerance ◽

Clustering Analysis ◽

Growth And Development ◽

Citrullus Lanatus ◽

Germplasm Collection ◽

Normal Growth ◽

Seedling Stage ◽

Breeding Lines ◽

Germplasm Collections ◽

Drought Tolerant

Because of the growing threat of global warming, drought stress could severely affect the normal growth and development of crop plants. To alleviate such an adverse effect, there is a need to screen watermelon germplasm collections to identify genetic sources for potential drought tolerance. In the present study, 820 accessions of USDA's Citrullus PIs and 246 watermelon breeding lines were evaluated for their drought tolerance at the seedling stage under extreme water stress conditions in a greenhouse. Significant variations in drought tolerance were observed in the Citrullus germplasm collections. Using fast clustering analysis, the tested watermelon materials could be assigned into four groups, including tolerant, intermediate tolerant, moderately sensitive, and sensitive, respectively. The most drought-tolerant Citrullus germplasm, including 13 Citrullus lanatus var. lanatus and 12 C. lanatus var. citroides accessions, were originated from Africa. These genetic materials could be used for rootstock breeding or for developing drought-tolerant watermelon cultivars.

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From qualitative to quantitative: a new approach for determining heat tolerance in cotton using triphenyl tetrazolium chloride

10.21203/rs.3.rs-35212/v1 ◽

2020 ◽

Author(s):

Susan Yvonne Jaconis ◽

Warren C Conaty ◽

Alan J. E. Thompson ◽

Shanna L Smith ◽

Chiara Trimarchi ◽

...

Keyword(s):

Heat Stress ◽

High Temperature ◽

Temperature Stress ◽

Heat Tolerance ◽

High Temperature Stress ◽

Triphenyl Tetrazolium Chloride ◽

Improvement Program ◽

Breeding Programs ◽

Tetrazolium Chloride ◽

Viability Testing

Abstract Background Susceptibility of cotton to heat stress in cotton production systems is a major concern for breeding programs. It is hypothesised that in order to maintain or improve cotton yields and quality in sub-optimal future climates, the negative effects of high temperature stress must be mitigated. To address this need, a fast and effect way of quantifying thermotolerant phenotypes is required. Triphenyl tetrazolium chloride (TTC) based enzyme viability testing following high temperature stress can be used as a heat tolerance phenotype. This is because when live cells encounter a TTC solution, TTC undergoes a chemical reduction producing a visible, insoluble red product called triphenyl formazan, that can be quantified spectrophotometrically. However, existing TTC based cell viability assays cannot easily be deployed at the scale required in a crop improvement program. Results In this study, a heat stress assay (HSA) based on the use of TTC enzyme viability testing has been refined and improved for efficiency, reliability, and ease of use through four experiments. Sampling factors which may influence assay results such as leaf age, plant water status, and short-term cold storage were also investigated. Experiments conducted in this study have successfully down scaled the assay and identified an optimal sampling regime, enabling measurement of large segregating populations for application in breeding programs. The optimal durations of leaf disc exposure to TTC and the subsequent extraction of the formazan product in ethanol were identified as 16 h and 13 h, respectively; leading to enhanced clarity of assay results. Conclusions These improvements in the methodology provide a new level of confidence in results, ensuring applicability of the assay to a breeding program. The improved HSA methodology is important as it is proposed that long-term improvements in cotton thermotolerance can be achieved through concurrent selection of superior phenotypes based on the HSA and yield performance in hot environments. Additionally, a new way of interpreting both heat tolerance and heat resistance were developed to differentiate genotypes that perform well at the time of a heat stress event and those that maintain a similar level of performance to a non-stressed control.

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Drought Tolerance and Application of Marker-Assisted Selection in Sorghum

Biology ◽

10.3390/biology10121249 ◽

2021 ◽

Vol 10 (12) ◽

pp. 1249

Author(s):

Andekelile Mwamahonje ◽

John Saviour Yaw Eleblu ◽

Kwadwo Ofori ◽

Santosh Deshpande ◽

Tileye Feyissa ◽

...

Keyword(s):

Drought Tolerance ◽

Qtl Mapping ◽

Marker Assisted Selection ◽

Sub Saharan Africa ◽

Stay Green ◽

Qtl Pyramiding ◽

Drought Tolerant ◽

Sub Saharan ◽

Food And Nutritional Security ◽

Marker Assisted Backcrossing

Sorghum is an important staple food crop in drought prone areas of Sub-Saharan Africa, which is characterized by erratic rainfall with poor distribution. Sorghum is a drought-tolerant crop by nature with reasonable yield compared to other cereal crops, but such abiotic stress adversely affects the productivity. Some sorghum varieties maintain green functional leaves under post-anthesis drought stress referred to as stay-green, which makes it an important crop for food and nutritional security. Notwithstanding, it is difficult to maintain consistency of tolerance over time due to climate change, which is caused by human activities. Drought in sorghum is addressed by several approaches, for instance, breeding drought-tolerant sorghum using conventional and molecular technologies. The challenge with conventional methods is that they depend on phenotyping stay-green, which is complex in sorghum, as it is constituted by multiple genes and environmental effects. Marker assisted selection, which involves the use of DNA molecular markers to map QTL associated with stay-green, has been useful to supplement stay-green improvement in sorghum. It involves QTL mapping associated with the stay-green trait for introgression into the senescent sorghum varieties through marker-assisted backcrossing by comparing with phenotypic field data. Therefore, this review discusses mechanisms of drought tolerance in sorghum focusing on physiological, morphological, and biochemical traits. In addition, the review discusses the application of marker-assisted selection techniques, including marker-assisted backcrossing, QTL mapping, and QTL pyramiding for addressing post-flowering drought in sorghum.

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Combining Ability of Extra-Early Maize Inbreds Derived from a Cross between Maize and Zea diploperennis and Hybrid Performance under Contrasting Environments

Agronomy ◽

10.3390/agronomy10081069 ◽

2020 ◽

Vol 10 (8) ◽

pp. 1069

Author(s):

Isaac K. Amegbor ◽

Baffour Badu-Apraku ◽

Gloria B. Adu ◽

Joseph Adjebeng-Danquah ◽

Johnson Toyinbo

Keyword(s):

Grain Yield ◽

Combining Ability ◽

Sub Saharan Africa ◽

Hybrid Breeding ◽

Optimal Conditions ◽

Breeding Programs ◽

Rainfed Conditions ◽

Genetic Mechanisms ◽

Maize Inbreds ◽

Sub Saharan

Knowledge of the genetic mechanisms conditioning drought tolerance in maize is crucial to the success of hybrid breeding programs aimed at developing high-yielding cultivars under drought. The objectives of this study were to determine the combining ability of extra-early inbreds, compute the heritability of measured traits, assess the performance of inbreds in hybrid combinations and investigate the associations among traits under drought and optimal conditions. A total of 252 hybrids generated by crossing 63 inbreds to four testers, along with four commercial hybrid checks, were evaluated for 2 years under drought and rainfed conditions. General combining ability (GCA) and specific combining ability (SCA) for the traits were significant. A total of 57.1% and 53.4% of the genotypic sum of squares were attributable to GCA effects for grain yield under managed drought and rainfed conditions, respectively. Hybrids TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 13 out-yielded the best checks under drought and optimal conditions by 49.13% and 39.05%, respectively. The most promising hybrids with consistently high grain yield under drought and rainfed conditions, were TZdEEI 54 × TZEEI 13, TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 21 and should be further evaluated for possible commercial production in sub-Saharan Africa.

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Agronomic, physiological and molecular characterization of rice mutants revealed key role of ROS and catalase in high temperature stress tolerance

10.1101/739433 ◽

2019 ◽

Cited By ~ 3

Author(s):

Syed Adeel Zafar ◽

Amjad Hameed ◽

Muhammad Ashraf ◽

Abdus Salam Khan ◽

Zia-ul-Qamar ◽

...

Keyword(s):

Heat Stress ◽

High Temperature ◽

Temperature Stress ◽

Heat Tolerance ◽

High Temperature Stress ◽

Early Growth ◽

Growth Stages ◽

Breeding Programs ◽

Selection Indices ◽

Heat Tolerant

AbstractPlants adapt to harsh environments particularly high temperature stress by regulating their physiological and biochemical processes, which are key tolerance mechanisms. Thus, identification of heat-tolerant rice genotypes and reliable selection indices are crucial for rice improvement programs. Here, we evaluated the response of a rice mutant population for high-temperature stress at the seedling and reproductive stages based on agronomic, physiological and molecular traits. The estimate of variance components revealed significant differences (P<0.001) among genotypes, treatments and their interaction for almost all traits. Principal component analysis showed significant diversity among the genotypes and traits under high-temperature stress. The mutant ‘HTT-121’ was identified as the most heat tolerant mutant with higher grain yield, panicle fertility, cell membrane thermo-stability (CMTS) and antioxidant enzyme levels under heat stress conditions. Various seedling-based morpho-physiological traits (leaf fresh weight, relative water contents, malondialdehyde, CMTS) and biochemical traits (superoxide dismutase, catalase and hydrogen peroxide) explained variations in grain yield that could be used as selection indices for heat tolerance in rice at early growth stages. Notably, heat sensitive mutants showed a significant accumulation of ROS level, reduced activities of catalase and upregulation of OsSRFP1 expression under heat stress, suggesting their key role in regulating heat tolerance in rice. The heat-tolerant mutants identified in this study could be used in breeding programs and the development of mapping populations to unravel the underlying genetic architecture for heat-stress adaptability.Summary text for table of contentsHeat stress probably due to changing climate scenario has become a serious threat for global rice production. On the other side, efforts to develop high yielding cultivars have led to the reduced genetic variability to withstand harsh environmental conditions. This study aimed to identify novel heat tolerant mutants developed through gamma irradiation which will provide a unique genetic resource for breeding programs. Further, we have identified reliable selection indices for screening heat-tolerant rice germplasm at early growth stages.

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