Drought Tolerant Wheat Genotypes Research Articles

Screening Wheat Genotypes for Specific Genes Linked to Drought Tolerance.

Drought stress, which significantly affects growth and reduces grain yield, is one of the main problems for wheat crops. Producing promising drought-tolerant wheat cultivars with high yields is one of the main targets for wheat breeders. In this study, a total of seven drought-tolerant wheat genotypes were screened for the presence of 19 specific drought tolerance genes. The genotypes were tested under normal and drought conditions for two growing seasons. Four spike traits, namely, spike length (SPL), grain number per spike (GNPS), number of spikelets per spike (NSPS), and grain yield per spike (GYPS), were scored. The results revealed that drought stress decreased the SPL, GNPS, NSPS, and GYPS, with ranges ranging from 2.14 (NSPS) to 13.92% (GNPS) and from 2.40 (NSPS) to 11.09% (GYPS) in the first and second seasons, respectively. ANOVA revealed high genetic variation among the genotypes for each trait under each treatment. According to the drought tolerance indices, Omara 007 presented the highest level of drought tolerance (average of sum ranks = 3), whereas both Giza-36 genotypes presented the lowest level of drought tolerance (average of sum ranks = 4.8) among the genotypes tested. Among the 19 genes tested, 11 were polymorphic among the selected genotypes. Omara 007 and Omara 002 presented the greatest number of specific drought tolerance genes (nine) tested in this study, whereas Sohag-5, Giza-36, and PI469072 presented the lowest number of drought tolerance genes (four). The number of different genes between each pair of genotypes was calculated. Seven different genes were found between Omara 007 and Giza-36, Omara 007 and Sohag-5, and Omara 002 and PI469072. The results of this study may help to identify the best genotypes for crossing candidate genotypes, and not merely to genetically improve drought tolerance in wheat.

Physiological, biochemical and hormonal response of wheat cultivars to foliar application of growth stimulants and zinc nano-chelate under water deficit stress

To investigate the effect of different foliar application treatments to improve drought tolerance in wheat genotypes, a factorial split-plot experiment was conducted based on the randomized complete block design with 3 replications in 2 locations. The main factor was irrigation (normal and water deficit) and the secondary factors were 4 levels of foliar application (control: without foliar application, jasmonic acid, zinc nano-chelate and succinate) and 3 genotypes of barley. Water deficit stress reduced the content of chlorophyll a (9.03%), chlorophyll b (6.66%), total chlorophyll (7.32%) and auxin (4.21%) and increased the catalase (18.18%), superoxide dismutase activity (23.35%), malondialdehyde (7.17%), glucose (5.35%), fructose (4.85%) and sucrose (14.99%) versus normal irrigation conditions. Foliar application of zinc nano-chelate increased chlorophyll a, chlorophyll b, total chlorophyll and fructose content by 15.45%, 15.76%, 14.70% and 41.35% respectively. The highest content of chlorophyll a, chlorophyll b and total chlorophyll was assigned to the Mihan cultivar. Foliar application with zinc nano-chelate in both environments resulted in the highest biological yield and grain yield and the lowest content of abscisic acid. Foliar application line 9 genotypes with zinc nano-chelate had the highest auxin, cytokinin, catalase and superoxide dismutase activity. While foliar application of nano-zinc chelate in the Mihan cultivar led to the highest biological yield, grain yield, glucose content and the lowest amount of malondialdehyde. Therefore, foliar application of zinc nano-chelate along with the appropriate variety can improve grain yield under different environmental conditions.

The Quest for Reliable Drought Stress Screening in Tetraploid Wheat (Triticum turgidum spp.) Seedlings: Why MDA Quantification after Treatment with 10% PEG-6000 Falls Short.

Drought stress poses significant productivity challenges to wheat. Several studies suggest that lower malondialdehyde (MDA) content may be a promising trait to identify drought-tolerant wheat genotypes. However, the optimal polyethylene glycol (PEG-6000) concentration for screening seedlings for drought tolerance based on MDA quantification is not clear. The aim of this study was to verify whether a 10% (w/v) PEG-6000 concentration-induced water stress was reliable for discriminating between twenty-two drought-susceptible and drought-tolerant tetraploid wheat (Triticum turgidum spp. durum, turanicum, and carthlicum) accessions based on MDA quantification. To do so, its correlation with morpho-physiological traits, notoriously related to seedling drought tolerance, i.e., Seedling Vigour Index and Seedling Water Content, was evaluated. Results showed that MDA content was not a reliable biomarker for drought tolerance, as it did not correlate significantly with the aforementioned morpho-physiological traits, which showed, on the contrary, high positive correlation with each other. Combining our study with the cited literature, it clearly emerges that different wheat genotypes have different "water stress thresholds", highlighting that using a 10% PEG-6000 concentration for screening wheat seedlings for drought tolerance based on MDA quantification is not reliable. Given the conflicting results in the literature, this study provides important insights for selecting appropriate methods for evaluating wheat seedling drought tolerance.

Drought tolerance of wheat genotypes is associated with rhizosphere size and enzyme system

Drought tolerance of wheat genotypes is associated with rhizosphere size and enzyme system

Combining Genetic and Phenotypic Analyses for Detecting Bread Wheat Genotypes of Drought Tolerance through Multivariate Analysis Techniques.

Successfully promoting drought tolerance in wheat genotypes will require several procedures, such as field experimentations, measuring relevant traits, using analysis tools of high precision and efficiency, and taking a complementary approach that combines analyses of phenotyping and genotyping at once. The aim of this study is to assess the genetic diversity of 60 genotypes using SSR (simple sequence repeat) markers collected from several regions of the world and select 13 of them as more genetically diverse to be re-evaluated under field conditions to study drought stress by estimating 30 agro-physio-biochemical traits. Genetic parameters and multivariate analysis were used to compare genotype traits and identify which traits are increasingly efficient at detecting wheat genotypes of drought tolerance. Hierarchical cluster (HC) analysis of SSR markers divided the genotypes into five main categories of drought tolerance: four high tolerant (HT), eight tolerant (T), nine moderate tolerant (MT), six sensitive (S), and 33 high sensitive (HS). Six traits exhibit a combination of high heritability (>60%) and genetic gain (>20%). Analyses of principal components and stepwise multiple linear regression together identified nine traits (grain yield, flag leaf area, stomatal conductance, plant height, relative turgidity, glycine betaine, polyphenol oxidase, chlorophyll content, and grain-filling duration) as a screening tool that effectively detects the variation among the 13 genotypes used. HC analysis of the nine traits divided genotypes into three main categories: T, MT, and S, representing three, five, and five genotypes, respectively, and were completely identical in linear discriminant analysis. But in the case of SSR markers, they were classified into three main categories: T, MT, and S, representing five, three, and five genotypes, respectively, which are both significantly correlated as per the Mantel test. The SSR markers were associated with nine traits, which are considered an assistance tool in the selection process for drought tolerance. So, this study is useful and has successfully detected several agro-physio-biochemical traits, associated SSR markers, and some drought-tolerant genotypes, coupled with our knowledge of the phenotypic and genotypic basis of wheat genotypes.

Genotypic Differences in Morphological, Physiological and Agronomic Traits in Wheat (Triticum aestivum L.) in Response to Drought.

Drought is one of the main environmental factors affecting crop growth, and breeding drought-tolerant cultivars is one of the most economic and effective ways of increasing yields and ensuring sustainable agricultural production under drought stress. To facilitate the breeding of drought-tolerant wheat, this study was conducted to evaluate genotypic differences in the drought tolerance of 334 wheat genotypes collected from China and Australia with the aim of screening for drought-tolerant and -sensitive genotypes and to elucidate the corresponding physiological mechanisms. A hydroponic-air experiment (roots exposed to air for 7 h/d and continued for 6 d) showed significant genotypic differences in shoot and root dry weights among the genotypes. The relative shoot and root dry weights, expressed as the percentage of the control, showed a normal distribution, with variation ranges of 20.2-79.7% and 32.8-135.2%, respectively. The coefficients of variation were in the range of 18.2-22.7%, and the diversity index was between 5.71 and 5.73, indicating a rich genetic diversity among the wheat genotypes for drought tolerance. Using phenotypic differences in relative dry weights in responses to drought stress, 20 of each of the most drought-tolerant and drought-sensitive genotypes were selected; these were further evaluated in pot experiments (watering withheld until the soil moisture content reached four percent). The results showed that the trends in drought tolerance were consistent with the hydroponic-air experiment, with genotypes W147 and W235 being the most drought-tolerant and W201 and W282 the most sensitive. Significant genotypic differences in water use efficiency in response to drought were observed in the pot experiment, with the drought-tolerant genotypes being markedly higher and the two sensitive genotypes being no different from the control. A marked increase in bound water content in the drought stress plants was observed in the two drought-tolerant genotypes, while a decrease occurred in the free water. The reductions in photochemical efficiencies of PSII, transpiration rates, net photosynthesis rates, chlorophyll contents and stomatal conduction in the drought-sensitive genotypes W201 and W282 under drought stress were higher than the two tolerant genotypes. This study provides a theoretical guide and germplasm for the further genetic improvement of drought tolerance in wheat.

Early Detection of Drought Stress in Durum Wheat Using Hyperspectral Imaging and Photosystem Sensing

Wheat, being the third largest U.S. crop and the principal food grain, faces significant risks from climate extremes such as drought. This necessitates identifying and developing methods for early water-stress detection to prevent yield loss and improve water-use efficiency. This study investigates the potential of hyperspectral imaging to detect the early stages of drought stress in wheat. The goal is to utilize this technology as a tool for screening and selecting drought-tolerant wheat genotypes in breeding programs. Additionally, this research aims to systematically evaluate the effectiveness of various existing sensors and methods for detecting early stages of water stress. The experiment was conducted in a durum wheat experimental field trial in Maricopa, Arizona, in the spring of 2019 and included well-watered and water-limited treatments of a panel of 224 replicated durum wheat genotypes. Spectral indices derived from hyperspectral imagery were compared against other plant-level indicators of water stress such as Photosystem II (PSII) and relative water content (RWC) data derived from proximal sensors. Our findings showed a 12% drop in photosynthetic activity in the most affected genotypes when compared to the least affected. The Leaf Water Vegetation Index 1 (LWVI1) highlighted differences between drought-resistant and drought-susceptible genotypes. Drought-resistant genotypes retained 43.36% more water in leaves under well-watered conditions compared to water-limited conditions, while drought-susceptible genotypes retained only 15.69% more. The LWVI1 and LWVI2 indices, aligned with the RWC measurements, revealed a strong inverse correlation in the susceptible genotypes, underscoring their heightened sensitivity to water stress in earlier stages. Several genotypes previously classified based on their drought resistance showed spectral indices deviating from expectations. Results from this research can aid farmers in improving crop yields by informing early management practices. Moreover, this research offers wheat breeders insights into the selection of drought-tolerant genotypes, a requirement that is becoming increasingly important as weather patterns continue to change.

OSMOTIC ADJUSTMENT AND DROUGHT RESISTANCE OF WHEAT (TRITICUM AESTIVUM L.) - A SHORT REVIEW

Drought is the most limiting environmental factor affecting wheat growth and productivity and thus, breeding for drought tolerance is a main objective for cereal breeders. Progress in drought tolerance breeding of wheat depends upon genetic diversity existing among genotypes about of their responses to different stressors. One of the physiological parameter is the osmotic adjustment can be enhanced through selection and breeding. Osmotic adjustment is the only cellular process that is activated under water stress conditions and that makes it possible to maintain cellular turgor. This study presents some physiological patterns in wheat plants under drought condition, with focus on osmotic adjustment. The used methods included searching of databases, such as Web of Science or Google Scholar, in order to identify relevant results. Crop plants synthesize several osmolytes to provide osmotic balance at the cellular level, and those osmolytes, under drought stress, provide the plants’ osmotic adjustment. Osmotic adjustment is critical for regulating cell turgor for the maintenance of plant metabolic activity, growth, and productivity. Generally, drought tolerant wheat genotypes show a clear response towards osmotic adjustment. This indicates the key role that osmotic adjustment plays in drought tolerance and yield sustainability under drought stress.

Identification of drought tolerant wheat (Triticum aestivum) genotypes using stress tolerance indices in the western terai region of Nepal

Drought is the leading abiotic factor influencing global wheat production. To evaluate the drought performance of wheat genotypes, it is essential to identify and employ stress tolerance indices. These indices are essential for evaluating variation among genotypes in their response to drought, ultimately contributing to the development of more resilient and sustainable wheat production systems worldwide.. Thus, a field experiment was conducted in alpha lattice design with twenty genotypes including three checks viz., Bhrikuti, Gautam, and RR 21 at Institute of Agriculture and Animal Science (IAAS), Paklihawa Campus, Rupandehi, Nepal, under irrigated and drought conditions, to identify drought tolerance wheat in winter season of 2022. In irrigated condition, five irrigations were applied at different critical growth stages. Whereas in drought conditions, only initial irrigation was applied after field preparation, for the germination of seed, and a poly house was constructed, to restrict all forms of natural precipitation. Genotypes were harvested when they attained harvestable maturity, grain yield was recorded, and stress tolerance indices were calculated. The mean grain yield reduction was 86.88 % in drought condition. Correlation analysis showed that Yield under Stress conditions (Ys) had a significant positive correlation with Yield Stability Index (YSI)(0.911**), Geometric Mean Productivity (GMP)(0.918**), and Stress Tolerant Index (STI)(0.911**). Thus, YSI, GMP, and STI are the important stress tolerance indices considered while selecting drought tolerance genotypes. Principal component and biplot analysis revealed that Bhrikuti, BL 5116, NL 1447, NL 1508, and Gautam were stable and high-yielding drought tolerant wheat genotypes.

Assessment of genetic variation among wheat genotypes for drought tolerance utilizing microsatellite markers and morpho-physiological characteristics

Drought is a major abiotic stress that severely limits sustainable wheat (Triticum aestivum L.) productivity via morphological and physio-biochemical alterations of cellular processes. The complex nature and polygenic control of drought tolerance traits make breeding tolerant genotypes quite challenging. However, naturally occurring variabilities among wheat germplasm resources could potentially help combating drought. The present study was conducted to assess the drought tolerance of 18 Bangladeshi hexaploid wheat genotypes, focusing on the identification of potent sources of diversity by combining microsatellite markers, also known as single sequence repeat markers, and morpho-physiological characteristics that might help accelerating wheat crop improvement programs. Initially, the genotypes were evaluated using 25 microsatellite markers followed by an on-field evaluation of 7 morphological traits (plant height, spike number, spike length, grains per spike, 1000-grain weight, grain yield, biological yield) and 6 physiological traits (SPAD value, membrane stability index, leaf relative water content, proline content, canopy temperature depression, and leaf K+ ion content). The field-trial was conducted in a factorial fashion of 18 wheat genotypes and two water regimes (control and drought) following a split-plot randomized complete block design. Regardless of genotype, drought was significantly damaging for all the tested traits; however, substantial variability in drought stress tolerance was evident among the genotypes. Spike length, 1000-grain weight, SPAD value, leaf relative water content, canopy temperature depression, proline content, and potassium (K+) ion content were the most representative of drought-induced growth and yield impairments and also correlated well with the contrasting ability of genotypic tolerance. Microsatellite markers amplified 244 alleles exhibiting 79% genetic diversity. Out of 25 markers, 23 was highly polymorphic showing 77% average polymorphism. Morpho-physiological trait-based hierarchical clustering and microsatellite marker-based neighbor-jointing clustering both revealed three genotypic clusters with 71% co-linearity between them. In both cases, the genotypes Kanchan, BAW-1147, BINA Gom 1, BARI Gom 22, BARI Gom 26, and BARI Gom 33 were found to be comparatively more tolerant than the other tested genotypes, showing potential for cultivation in water-deficit environments. The findings of this study would contribute to the present understanding of drought tolerance in wheat and would provide a basis for future genotype selection for drought-tolerant wheat breeding programs.

Field identification of drought tolerant wheat genotypes using canopy vegetation indices instead of plant physiological and biochemical traits

Seasonal drought is a major limiting factor for wheat production in the North China Plain. The use of non-destructive screening tools based on vegetation indices associated with physiological and biochemical traits will help in the identification of drought-tolerant wheat genotypes to counter drought stress. The objectives of this study were to characterize the performance of 10 wheat genotypes with different genetic backgrounds in terms of physical and biochemical traits under two contrasting moisture regimes, and to evaluate the effectiveness of vegetation indices/spectral measurement techniques for assessing drought tolerance in wheat. Traits associated with drought stress were assessed in the 10 wheat genotypes, including plant biophysical parameters, drought tolerance parameters, as well as various vegetation indices. Significant variability was found wheat genotypes with different genetic backgrounds to water stress. The clustering results indicated that Luohan-19, Luohan-22, and Jinmai-47 were drought-tolerant genotypes characterized by high stress tolerance index (STI) values (0.548, 0.535 and 0.523, respectively), drought index (DI) values (0.517, 0.524 and 0.504, respectively), and drought tolerance coefficient (DC) values (1.065, 1.074 and 1.000, respectively). Based on principal component analysis and membership function, genotypes were classified as tolerant (Luohan-19, Luohan-22, and Jinmai-47), moderately tolerant (Luomai-26, Zhongmai-175, and Bainong-207) and sensitive (Yunong-516, Zhongmai-895, Annong-0711 and Huacheng-3366) to water stress, with comprehensive evaluation values (D) of >0.761, 0.422–0.761, and <0.422, respectively. Heatmap analysis of various vegetation indices for screening wheat genotypes showed similar results to the multivariate data analysis; that is, genotypes Luohan-19, Luohan-22, and Jinmai-47 were identified as drought-tolerant genotypes. Among these vegetation indices, the normalized difference water index (NDWI) and the red edge chlorophyll index (CIred edge) were highly correlated with the drought tolerance indices, such as STI and DI (r2 >0.717), and are therefore recommended as rapid indicators for the identification of tolerance genotypes in the field. These vegetation indices, particularly NDWI and CIred edge, exhibited similar performance to the drought tolerance indices and multivariate data analysis results in identifying drought-tolerant genotypes, and thus they can be used as alternative and inexpensive measures for identifying drought tolerance in wheat in the future.

Field Screening of Drought and Salinity Tolerant Wheat Genotypes in Hot and Dry Climates

Field Screening of Drought and Salinity Tolerant Wheat Genotypes in Hot and Dry Climates

Evaluation of bread wheat (Triticum aestivum L.) genotypes for drought tolerance using morpho-physiological traits under drought-stressed and well-watered conditions.

Increasing frequency of drought spells occasioned by changing climatic conditions, coupled with rise in demand for bread wheat, calls for the development of high yielding drought resilient genotypes to enhance bread wheat production in areas with moisture deficit. This study was designed to identify and select drought-tolerant bread wheat genotypes using morpho-physiological traits. One hundred and ninety-six bread wheat genotypes were evaluated in greenhouse and field experiments, under well-watered (80% of field capacity) and drought-stressed (35% of field capacity) conditions, for two years. Data were collected on five morphological traits (flag leaf size, flag leaf angle, flag leaf rolling, leaf waxiness and resistance to diseases) and 14 physiological traits. Relative water content (RWC), Excised leaf water retention (ELWR), Relative water loss (RWL), Leaf membrane stability index (LMSI), as well as Canopy temperature depression (CTD) at heading (CTDH), anthesis (CTDA), milking (CTDM), dough stage (CTDD) and ripening (CTDR) were estimated. Similarly, leaf chlorophyll content (SPAD reading) was recorded at heading (SPADH), anthesis (SPADA), milking (SPADM), dough stage (SPADD), and ripening (SPADR). Significant (p<0.01) genotypic differences were found for the traits under both well-watered and drought-stressed conditions. Associations of RWL with SPADH, SPADA, SPADM, SPADD and SPADR were significant (p<0.01) and negative under both watering regimes. The first three principal components accounted for 92.0% and 88.4% of the total variation under well-watered and drought-stressed conditions, respectively and comprised all the traits. The traits CTDD, CTDM, CTDR, SPADH, SPADA, SPADM, SPADD and SPADR with genotypes Alidoro, ET-13A2, Kingbird, Tsehay, ETBW 8816, ETBW 9027, ETBW9402, ETBW 8394 and ETBW 8725 were associated under both conditions. Genotypes with narrow flag leaves, erect flag leaf angles, fully rolled flag leaves, heavily waxed leaves, and resistant to disease manifested tolerance to drought stress. The identified traits and genotypes could be exploited in future breeding programmes for the development of bread wheat genotypes with tolerance to drought.

Evaluation of functional kompetitive allele-specific PCR (KASP) markers for selection of drought-tolerant wheat (Triticum aestivum) genotypes.

Wheat (Triticum aestivum ) is a major crop around the globe and different techniques are being used for its productivity enhancement. Germplasm evaluation to improve crop productivity mainly depends on accurate phenotyping and selection of genotypes with a high frequency of superior alleles related to the trait of interest. Therefore, applying functional kompetitive allele-specific PCR (KASP) markers for drought-related genes is essential to characterise the genotypes for developing future climate-resilient wheat crop. In this study, eight functional KASP markers and nine morphological traits were employed to evaluate the 40 wheat genotypes for drought tolerance. Morphological traits showed significant variation (P ≤0.05) among the genotypes, except tiller count (TC), fresh root weight (FRW) and dry root weight (DRW). PCA biplot showed that 63.3% phenotypic variation was explained by the first two PCs under control treatment, while 70.8% variation was explained under drought treatment. It also indicated that root length (RL) and primary root (PR) have considerable variations among the genotypes under both treatments and are positively associated with each other. Hence, the findings of this study suggested that both these traits could be used as a selection criterion to classify the drought-tolerant wheat genotypes. KASP genotyping accompanied by morphological data revealed that genotypes Markaz, Bhakar Star, China 2, Aas and Chakwal-50 performed better under drought stress. These outperforming genotypes could be used as parents in developing drought-tolerant wheat genotypes. Hence, KASP genotyping assay for functional genes or significant haplotypes and phenotypic evaluation are prerequisites for a modern breeding program.

Multi-trait selection of wheat lines under drought-stress condition

The immediate need for the increase in wheat production to meet the future world demand, associated with the occurrence of drastic climatic events, such as drought, makes it necessary to develop drought-resilient genotypes. The aims of this work were to evaluate the use of drought-tolerance indices for the selection of wheat genotypes, to compare the genetic gains in grain yield using different selection strategies by means of a multi-trait index, and to select superior drought-tolerant wheat genotypes. The total of 31 tropical wheat lines was evaluated in two experiments. Five agronomic traits were accessed. The grain yield data from the stress and nonstress experiments were used to obtain five drought-tolerance indices. The data were subjected to mixed model analysis, and four selection scenarios were designed. There was a significant effect of genotype for all traits. The inclusion of drought-tolerance indices in the selection index provided superior genetic gains in drought condition. Seven lines were selected due the high frequency of favorable alleles for drought-tolerance and other important agronomic traits. Drought-tolerance indices are appropriate for characterizing the response of wheat genotypes to drought-stress. The inclusion of drought-tolerance indices along with agronomic traits in multi-trait selection strategies provides for superior gains in grain yield compared to the non-inclusion of the indices.

Assessment of some bread wheat (Triticum aestivum L.) genotypes for drought tolerance using SSR and ISSR markers

As a result of the rapid increase in the world population, the need for wheat, which is one of the main nutrition in the human diet, is also rapidly increases. However, due to yield losses caused by abiotic stress factors such as drought, wheat production is not sufficient. Therefore, genetic characterization studies performed on wheat genotypes in terms of drought tolerance are important. In this study, genetic characterization of wheat genotypes regardingdrought tolerance was carried out by using molecular markers associated with drought-tolerance genes. For this purpose, 14 polymorphic markers were used to be able to distinguish between the control groups. Genetic characterization of 27 bread wheat genotypes by using eight ISSR markers revealed a polymorphism rate of 75.8%, and the mean PIC was calculated as 0.55. Based on the results of the genetic characterization performed with six SSR markers, the mean PIC value was 0.77, the mean He was 0.79, and the mean allele number was 6.7. In this study, the characterization of drought-tolerant and sensitive genotypes was carried out, and the potentials of genotypes for breeding studies were revealed. This study also indicates that used SSRs and ISSRs markers are useful in marker-assisted breeding about drought tolerance.

Canopy spectral reflectance indices correlate with yield traits variability in bread wheat genotypes under drought stress.

Drought stress is a major issue impacting wheat growth and yield worldwide, and it is getting worse as the world's climate changes. Thus, selection for drought-adaptive traits and drought-tolerant genotypes are essential components in wheat breeding programs. The goal of this study was to explore how spectral reflectance indices (SRIs) and yield traits in wheat genotypes changed in irrigated and water-limited environments. In two wheat-growing seasons, we evaluated 56 preselected wheat genotypes for SRIs, stay green (SG), canopy temperature depression (CTD), biological yield (BY), grain yield (GY), and yield contributing traits under control and drought stress, and the SRIs and yield traits exhibited higher heritability (H2) across the growing years. Diverse SRIs associated with SG, pigment content, hydration status, and aboveground biomass demonstrated a consistent response to drought and a strong association with GY. Under drought stress, GY had stronger phenotypic correlations with SG, CTD, and yield components than in control conditions. Three primary clusters emerged from the hierarchical cluster analysis, with cluster I (15 genotypes) showing minimal changes in SRIs and yield traits, indicating a relatively higher level of drought tolerance than clusters II (26 genotypes) and III (15 genotypes). The genotypes were appropriately assigned to distinct clusters, and linear discriminant analysis (LDA) demonstrated that the clusters differed significantly. It was found that the top five components explained 73% of the variation in traits in the principal component analysis, and that vegetation and water-based indices, as well as yield traits, were the most important factors in explaining genotypic drought tolerance variation. Based on the current study's findings, it can be concluded that proximal canopy reflectance sensing could be used to screen wheat genotypes for drought tolerance in water-starved environments.

Roots and shoot traits contributing to drought tolerance from germination to maturity stages for bread wheat

Drought is the major bottleneck for food security worldwide. Identifying reliable selection traits that sustain plant growth and productivity under water-deficient conditions is essential for releasing resilient drought tolerant wheat genotypes. Herein, in order to identify the best combination of drought tolerance related-traits, this study was carried out to assess the effect of 21 shoot and 17 root secondary traits on grain yield of 40 bread wheat genotypes from germination to maturity stages under laboratory, greenhouse and field conditions. In this research, germination rate (GR), mean germination time (MGT), roots weight (RW), roots number (RN) and Root : Shoot ratio (R/S) were relevant for discriminating drought tolerant genotypes, expressing negative moderate correlation (r~-0.5) and explaining a significant part of yield variation (8 to 30%). Grain number (GN) was the most important agronomic trait (r~0.70-0.94) which explained up to 88 % of yield variation. This latter effect is reinforced by the indirect effects of productive spikes number (FSN), thousand kernel weight (TKW) and grains number per fertile spike (GNFS). The biomass (BY), ground cover (GC), spike (SL) and pedoncule lengths (PL) were also relevant, especially under severe stress (r=0.4-0.6 ; β=0.33-0.40) ; while the canopy temperature depression (CTD) was determinant under moderate stress (r=-0.45 ; β=-0.46). Combined selection for these traits will be effective to improve the process of developing high-yielding bread wheat varieties adapted to drought prone areas.

Grain yield, chlorophyll and protein contents of elite wheat genotypes under drought stress

BackgroundDrought stress at different growth stages significantly alters growth, yield, and quality traits of wheat. However, great variability exists among genotypes regarding their response to drought stress. Therefore, determining the impacts of drought stress on yield and quality traits would help to select the superior genotypes. MethodsThis study investigated the effects of drought stress on wheat grain yield, chlorophyll, and protein contents. Fourteen (14) recently developed elite bread wheat (Triticum aestivum L.) genotypes were used in this study for evaluation under irrigated (full irrigation) and drought conditions (half of normal irrigation). The data relating to growth, yield and protein contents were recorded. ResultsSignificant differences (P ≤ 0.01) were noted among genotypes for all recorded traits. Drought stress significantly reduced the days to 50 % heading, days to 50 % maturity, grain filling, plant height (cm), number of spikes per m2, chlorophyll index (SPAD), peduncle length (cm), number of grains spike-1, thousand grain weight (g) and grain yield (kg ha−1). However, protein contents were increased under drought stress. Correlation analysis showed significant positive association of grain yield with thousand grain weight, number of spikes per m2, spike length, chlorophyll index, grain filling period and number of grains spike-1 under both irrigated and drought stress conditions. The protein contents expressed positive and negative relationship with yield under drought stress and irrigated conditions, respectively. Bioplot analysis revealed that genotype ‘V-19618′ and ‘V-19600′ proved superior under drought conditions regarding grain yield and related traits, while genotype ‘V-19574′ proved better under both irrigated and drought conditions. ConclusionsThese identified genotypes, i.e., ‘V-19618′ and ‘V-19600′ can be utilized in future wheat breeding programs to induce desirable characters for producing drought tolerant wheat genotypes.

Response of Bread Wheat Genotypes for Drought and Low Nitrogen Stress Tolerance

Drought stress and nitrogen (N) deficiency are the major causes of yield losses in bread wheat (Triticum aestivum) production. Breeding wheat cultivars with combined drought and low N stress tolerance is an economical approach for yield gains. The objective of this study was to evaluate the response of diverse bread wheat genotypes under drought and low N stress conditions to select high-performing genotypes for developing breeding populations and production to mitigate against drought and low N stress. Fifty bread wheat genotypes were evaluated under drought-stressed (DS) and non-stressed (NS) conditions and N application rates of 50, 100 and 200 kg N ha−1. The experiments were conducted in a controlled environment and field conditions during the 2019/20 cropping season. Data on grain yield and yield components were collected and subjected to statistical analysis. The four-way interaction involving genotype, water regime, N treatments and testing environment had a significant (p &lt; 0.05) effect on all assessed agronomic traits, suggesting that genotype response depended on the treatment combinations. Drought stress and 50 kg N ha−1 reduced grain yield by 20% compared to NS and 50 kg N ha−1. The grain yield ranged from 120 to 337 g/m2, with a mean of 228 g/m2 under DS. Under DS and 200 kg N ha−1, the genotype designated as SBO 19 had a higher grain yield of 337 g/m2, followed by SBO 22 (335 g/m2), SBO 16 (335 g/m2), SBO 04 (335 g/m2) and SBO 33 (335 g/m2). Grain yields under DS and 50 kg N ha−1, and NS and 50 kg N ha−1 had a positive and significant correlation (r &gt; 0.5; p &lt; 0.01) with most of the evaluated traits. Highly correlated traits directly contribute to total yield gain and should be incorporated during the selection of high-yielding genotypes. The study identified the 10 best lines that are high-yielding with early flowering and maturity under DS or NS conditions and the three N treatments. The selected lines are recommended as breeding parents to develop drought-adapted and N-use efficient genetic resources. The identified genotypes are important for sustainable wheat production and effective breeding of improved cultivars to mitigate drought stress and soil nutrient deficiencies, to ensure food security in Sub-Saharan Africa.