Use of an enhanced cultivar calibration framework for DSSAT to examine effects of ecotype and time-series data

In this study, the role of selenium nanoparticles (SeNPs, 10 mg·L−1) has been investigated in modulating the negative effects of drought and heat stresses on eight bread wheat (Triticum aestivum L.) genotype seedlings. Those genotypes included Giza-168, Giza-171, Misr-1, Misr-3, Shandweel-1, Sids-1, Sids-12, and Sids-14. The study included six treatments as follows: regular irrigation with 100% Field Capacity (FC) at a temperature of 23 ± 3 °C (T1), drought stress with 60% FC (T2), heat stress of 38 °C for 5 h·day−1 (T3), foliar spray of 10 mg·L−1 of SeNPs only (T4), a combination of drought stress with foliar spray of 10 mg·L−1 of SeNPs (T5), and heat stress with foliar spray of 10 mg·L−1 of SeNPs (T6). The experiment continued for 31 days. Foliar application of SeNPs improved the plant growth, morpho-physiological and biochemical responses, and expression of stress-responsive genes in wheat (T. aestivum L.) seedlings. Overall, morpho-physiological traits such as plant height (PH), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), and root dry weight (RDW) of wheat genotypes grown under different conditions ranged from 25.37–51.51 cm, 3.29–5.15 g, 0.50–1.97 g, 0.72–4.21 g, and 0.11–1.23 g, respectively. From the morpho-physiological perspective, drought stress had a greater detrimental impact on wheat plants than heat stress, whereas heat stress significantly impacted the expression of stress-responsive genes. Stress responses to drought and heat varied between wheat genotypes, suggesting that different genotypes are more resilient to stress. Exogenous spraying of 10 mg·L−1 of SeNPs improved the photosynthetic pigments, photosynthetic rate, gas exchange, and transpiration rate of wheat plants and enhanced drought and heat tolerance by increasing the activity of antioxidant enzymes including catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) and the expression level of stress-responsive genes. Our results showed that spraying wheat seedlings with 10 mg·L−1 of SeNPs enhanced SOD activity for all genotypes as compared to the control, with the Sids-12 genotype having the highest value (196.43 U·mg−1 FW·min−1) and the Giza-168 genotype having the lowest (152.30 U·mg−1 FW·min−1). The expression of PIP1, LEA-1, HSP70, and HSP90 stress-responsive genes was more significant in tolerant genotypes (Giza-171 and Giza-168) than in sensitive ones (Misr-1 and Misr-3) in response to drought and heat stresses. Under stress conditions, the shoot and root fresh weights, photosynthetic pigment content, stomatal conductance (SC), and transpiration rate (TR) were positively correlated with plant height (PH), while root and shoot dry weights, malondialdehyde (MDA), proline, hydrogen peroxide (H2O2), and APX were negatively correlated. Multivariate analysis and biplot results revealed that genotypes Giza-168, Giza-171, Sids-12, and Sids-14 performed well in both stress situations and were classified as stress-tolerant genotypes. These best genotypes may be employed in future breeding projects as tools to face climate change. This study concluded that various physio-biochemicals and gene expression attributes under drought and heat stress could be modulated by foliar application of SeNPs in wheat genotypes, potentially alleviating the adverse effects of drought and heat stress.

ABSTRACTDrought and heat are the two most important environmental constraints to wheat (Triticum aestivum L.) production globally and are predicted to become more severe with global climate change. A number of recent studies have reported quantitative trait loci (QTL) for yield and agronomic traits in drought and heat‐stressed environments and for physiological traits that contribute to improved performance under stress. The objective of this study was to perform a meta‐analysis of reported QTL to identify meta‐QTL (MQTL) associated with adaptation to drought and heat stress. In the studies analyzed, QTL were reported for 81 different traits across a range of environments including both field and controlled experiments. A total of 854 individual QTL were reported, with 502 associated with drought stress, 234 with heat stress, and 118 with physiological traits in nonstressed environments. Individual QTL clustered into 66 MQTL regions distributed throughout the genome. There were 43 MQTL that co‐localized for both drought and heat stress, 20 specific for drought stress, 2 specific for heat stress, and 1 MQTL specific for physiological traits in nonstressed environments. Quantitative trait loci for plant height, days to maturity, kernel weight, spike density, and canopy temperature were most significantly associated with QTL for yield. Integration of 137 single nucleotide polymorphism (SNP) markers for heat‐ and drought‐responsive candidate genes identified 50 SNPs within MQTL confidence intervals, including genes involved in sugar metabolism, scavenging of reactive oxygen species, and abscisic‐acid‐induced stomatal closure. Identified MQTL and candidate genes can be targeted for future studies and genetic improvement of abiotic stress tolerance in wheat.

Aegilops tauchii is a D-genome donor of hexaploid wheat and is a potential source of genes for various biotic and abiotic stresses including heat and drought. In the present study, we used multi-stage evaluation technique to understand the effects of heat and drought stresses on Ae. tauschii derived introgression lines (ILs). Preliminary evaluation (during stage-I) of 369 ILs for various agronomic traits identified 59 agronomically superior ILs. In the second stage (stage-II), selected ILs (i.e., 59 ILs) were evaluated for seedling heat (at 30°C and 35°C) and drought (at 20% poly-ethylene glycol; PEG) stress tolerance under growth chambers (stage-II). Heat and drought stress significantly reduced the seedling vigour by 59.29 and 60.37 percent, respectively. Genotype×treatment interaction analysis for seedling vigour stress tolerance index (STI) identified IL-50, IL-56, and IL-68 as high-performing ILs under heat stress and IL-42 and IL-44 as high-performing ILs under drought stress. It also revealed IL-44 and IL-50 as the stable ILs under heat and drought stresses. Furthermore, in the third stage (stage-III), selected ILs were evaluated for heat and drought stress tolerance under field condition over two cropping seasons (viz., 2020-21 and 2021-22), which significantly reduced the grain yield by 72.79 and 48.70 percent, respectively. Stability analysis was performed to identify IL-47, IL-51, and IL-259 as the most stable ILs in stage-III. Tolerant ILs with specific and wider adaptability identified in this study can serve as the potential resources to understand the genetic basis of heat and drought stress tolerance in wheat and they can also be utilized in developing high-yielding wheat cultivars with enhanced heat and drought stress tolerance.

Individual and combined effects of heat and drought and subsequent recovery on winter wheat (Triticum aestivum L.) photosynthesis, nitrogen metabolism, cell osmoregulation, and yield formation

The present study was conducted to determine genotypic variations for stem reserve mobilization efficiency in wheat (Triticum aestivum L.) under drought, heat and combined stresses along with defoliation. Genotypes (43) were evaluated under 4 field conditions namely, timely sown irrigated (control), timely sown rainfed (drought), delayed sown irrigated (heat) and delayed sown rainfed (combined heat and drought) by cutting off all leaf blades (defoliation) at 12 days after anthesis. The traits recorded were stem reserve mobilization efficiency (SRE), harvest index (HI), grain weight (GW) and specific weight (Sp. wt). In timely sown and delayed sown environment condition the average maximum temperature was 24.7°C and 30.4°C during flowering to maturity stage respectively. The average soil moisture under control, drought, heat and combined stress was 14.46, 6.68, 16.87 and 7.78% respectively. SRE was found significantly higher under drought stress followed by combined stress, control and heat stress. The correlation analysis revealed Sp.wt at 12 DAA was highly positively correlated with the GW. The trait SRE was highly positively correlated with HI. Combined analysis for all stresses showed that HD 4728, Duram 1, Chiriya 3, HD 2851, HD 2329, DBW 43 had highest and Hindi 62, WL 711, GCP 23, HD 2967, GCP 2, Kalyansona had lowest SRE. Genotypes were also grouped into different clusters based on their SRE. The genotypes with higher SRE can be used in breeding programmes or directly used as cultivars under drought, heat and combined stress conditions.

An experiment was conducted during winter (rabi) seasons of 2020–21 and 2021–22 at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to assess the impacts of heat and drought stresses, both individually and combined, on wheat (Triticum aestivum L.) plants during the reproductive stage. Four wheat genotypes (C306, HD2967, Raj3765 and WL711) were subjected to heat stress (H), drought stress (D) and combined heat, and drought stress (HD) conditions at the anthesis stage. The research investigated various physiological, biochemical and grain yield parameters, as well as the relative expression of genes involved in the proline and abscisic acid (ABA) metabolic pathways. Among the tested genotypes, Raj3765 exhibited decreased ABA levels and increased proline accumulation during the anthesis stage under both individual and combined stress conditions. Notably, Raj3765 also displayed highergrain yield compared to the other 3 genotypes under all stress conditions, indicating that elevated proline levels and reduced ABA levels likely contributed to its resilience. Furthermore, the study revealed that the combination of heat and drought stresses had a more severe detrimental effect on wheat plants compared to individual stress treatments. These findings underscore the significance of comprehensively studying combined stress conditions, as they can result in substantial yield losses in wheat crop development and productivity.

Within their natural habitat, crops are often subjected to drought and heat stress, which suppress crop growth and decrease crop production. Causing overaccumulation of glycinebetaine (GB) has been used to enhance the crop yield under stress. Here, we investigated the response of wheat (Triticum aestivum L.) photosynthesis to drought, heat stress and their combination with a transgenic wheat line (T6) overaccumulating GB and its wild-type (WT) Shi4185. Drought stress (DS) was imposed by controlling irrigation until the relative water content (RWC) of the flag leaves decreased to between 78 and 82%. Heat stress (HS) was applied by exposing wheat plants to 40°C for 4 h. A combination of drought and heat stress was applied by subjecting the drought-stressed plants to a heat stress as above. The results indicated that all stresses decreased photosynthesis, but the combination of drought and heat stress exacerbated the negative effects on photosynthesis more than exposure to drought or heat stress alone. Drought stress decreased the transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2 concentration (Ci), while heat stress increased all of these; the deprivation of water was greater under drought stress than heat stress, but heat stress decreased the antioxidant enzyme activity to a greater extent. Overaccumulated GB could alleviate the decrease of photosynthesis caused by all stresses tested. These suggest that GB induces an increase of osmotic adjustments for drought tolerance, while its improvement of the antioxidative defense system including antioxidative enzymes and antioxidants may be more important for heat tolerance.

BackgroundHexaploid wheat (Triticum aestivum) is a globally important crop. Heat, drought and their combination dramatically reduce wheat yield and quality, but the molecular mechanisms underlying wheat tolerance to extreme environments, especially stress combination, are largely unknown. As an allohexaploid, wheat consists of three closely related subgenomes (A, B, and D), and was reported to show improved tolerance to stress conditions compared to tetraploid. But so far very little is known about how wheat coordinates the expression of homeologous genes to cope with various environmental constraints on the whole-genome level.ResultsTo explore the transcriptional response of wheat to the individual and combined stress, we performed high-throughput transcriptome sequencing of seedlings under normal condition and subjected to drought stress (DS), heat stress (HS) and their combination (HD) for 1 h and 6 h, and presented global gene expression reprograms in response to these three stresses. Gene Ontology (GO) enrichment analysis of DS, HS and HD responsive genes revealed an overlap and complexity of functional pathways between each other. Moreover, 4,375 wheat transcription factors were identified on a whole-genome scale based on the released scaffold information by IWGSC, and 1,328 were responsive to stress treatments. Then, the regulatory network analysis of HSFs and DREBs implicated they were both involved in the regulation of DS, HS and HD response and indicated a cross-talk between heat and drought stress. Finally, approximately 68.4 % of homeologous genes were found to exhibit expression partitioning in response to DS, HS or HD, which was further confirmed by using quantitative RT-PCR and Nullisomic-Tetrasomic lines.ConclusionsA large proportion of wheat homeologs exhibited expression partitioning under normal and abiotic stresses, which possibly contributes to the wide adaptability and distribution of hexaploid wheat in response to various environmental constraints.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0511-8) contains supplementary material, which is available to authorized users.

The influence of drought and heat stress on the expression of end-use quality parameters of common wheat

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.

Drought stress (DS) and heat stress (HS) have adverse effects on wheat (Triticum aestivum L.) growth, serving as the primary constraints that significantly limit grain yield. Present study was carried out during 2020–21 and 2021–22 at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to evaluate the effects of drought and heat stress on grain quality parameters of 4 contrasting wheat genotypes. Several physiological and biochemical parameters were analyzed in wheat cv. C306 (thermotolerant), HD3271 (thermosusceptible), H11500 (drought tolerant) and HD3226 (drought susceptible) under DS and HS. Our study found that disintegration of chlorophyll pigments was higher in wheat cv. HD3226 (43%) under combined stress. Grain weight per spike was reduced by 30% in C306 and 47.3% in HD 3271 under combined drought and heat stress treatment. All cultivars showed reduction in starch, amylose, amylopectin, AGPase and Soluble starch synthase activity under DS and HS. Additionally, a significant increase in total soluble protein and free amino acid content were observed in all genotypes under combined stress. Chlorophyll content and grain weight per spike were positively correlated with the starch, amylose, amylopectin, soluble starch synthase and AGPase activity, while negatively related to the total soluble protein and free amino acid content. The tolerant genotypes maintained higher chlorophyll content, grain weight per spike, starch, amylose, amylopectin, soluble starch synthase and AGPase activity could be used for breeding, for the adaptation to drought and heat under climate change.

Stay-green (SG) and stem reserve mobilization (SRM) are two significant mutually exclusive traits, which contributes to grain-filling during drought and heat stress in wheat. The current research was conducted in a genome-wide association study (GWAS) panel consisting of 278 wheat genotypes of advanced breeding lines to find the markers linked with SG and SRM traits and also to screen the superior genotypes. SG and SRM traits, viz. soil plant analysis development (SPAD) value, canopy temperature (CT), normalized difference vegetation index (NDVI), leaf senescence rate (LSR) and stem reserve mobilization efficiency (SRE) were recorded. The trial was conducted in α-lattice design, under control and combined heat and drought stress (HD). Analysis of variance and descriptive statistics showed a significant difference across the evaluated traits. The highest mean of SRE (31.7%) and SRM (0.42g/stem) was reported in HD, while highest SRE in HD and lowest in control was 52.56% and 15.7%, respectively. Genotyping was carried out using the 35K Axiom R Wheat Breeder's Array, 14,625 SNPs were kept after filtering. Through GWAS, 36 significant marker trait associations (MTAs) were identified on 16 distinct chromosomes; out of this, 22 MTAs were found under control and 14 MTAs under HD. Candidate genes that code for UDP-glycosyltransferase 73C4-like and protein detoxification 40-like was linked to SPAD and CT respectively. One MTAs was detected for SRM on chromosome 6B that code for wall associated receptor kinase 4 like. These SNPs can be utilized to generate cultivars that adapt to climate change by a marker-assisted gene transfer.

The stability of wheat (Triticum aestivum L.) genotypes across diverse environments is crucial for breeding programmes aiming to improve yield potential and resilience to climate variability. The present study was carried out during winter (rabi) seasons of 2019–2020 and 2020–2021 at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana to evaluate 16 morphological traits in wheat under normal sown conditions, drought stress, heat stress and combined drought and heat stress utilizing the Eberhart and Russell stability model. The trial was conducted in randomized complete block design (RCBD). Significant genotype-by-environment (G × E) interactions were observed, underscoring the importance of selecting stable, high-yielding genotypes. Genotypes BRW 3806, DBW 303, and HD 2967 demonstrated superior yield stability across environments, making them ideal candidates for climate-resilient wheat breeding. Early-maturing genotypes DBW 110 and HD 2967 showed promise in escaping terminal heat stress, while genotypes with reduced plant height HD 2967, were well-suited for minimizing lodging risk. Spike and grain characteristics, including spike length and grain weight per spike, were directly correlated with higher yield potential, particularly in genotypes WH 1235 and BRW 3806. The study highlights the importance of integrating traits early maturity, reduced plant height and enhanced grain characteristics into aimed at enhancing wheat productivity and resilience are crucial for adapting to the challenges posed by climate change.

Abscisic acid (ABA) concentration in wheat (Triticum aestivum L.) plants increases during heat and drought stress and is associated with stomatal closure, low photosynthetic rate, and senescence. This research was conducted to determine if wheat somaclones selected in vitro for ABA insensitivity are resistant to heat and drought stress and to identify traits that contribute to stress resistance as ABA insensitivity is increased. Five ABA‐insensitive somadones and their parental line ND7532 were grown in Hoagland's solution until anthesis, then heat and osmotic stresses were applied through maturity. Heat stress was induced by increasing temperature from 25/20 to 35/25 °C, and osmotic stress (−0.05 MPa) was induced by adding 100 g kg−1 polyethylene glycol‐1000 (PEG‐1000) to the hydroponic solution. An exceptional somaclone KTC86211 and parent ND7532 were grown in 1:1:1 sand: Reading silt loam (fine, mixed, mesic Typic Argiudoil):peat. Heat stress was applied as in the first experiment, and drought stress (−0.5 MPa) was induced by withholding water after anthesis and soil water potential was monitored with a thermocouple psychrometer. The ABA‐insensitive somaclones KTC86211 and KTC86424 had significantly lower stomatal resistance, higher variable leaf chlorophyll fluorescence, longer leaf area duration, and greater kernel wt. and grain yield per plant than the parent in the first experiment. Crop growth rate, grain filling rate, and grain filling duration were higher in the ABA‐insensitive somaclone KTC86211 than in ND7532 in the second experiment, indicating that greater grain yield per plant resulted from rapid assimilation and translocation of nutrients and delayed senescence. We concluded that ABA‐insensitive genotypes may have high growth rates and long leaf area duration under stress and that selection for ABA insensitivity may be an effective approach to improving heat and drought resistance in wheat.

Crop yields are increasingly affected by climate change-induced weather extremes in Germany. However, there is still little knowledge of the specific crop-climate relations and respective heat and drought stress-induced yield losses. Therefore, we configure weather indices (WIs) that differ in the timing and intensity of heat and drought stress in wheat (Triticum aestivum L.). We construct these WIs using gridded weather and phenology time series data from 1995 to 2019 and aggregate them with Germany-wide municipality level on-farm wheat yield data. We statistically analyze the WI's explanatory power and region-specific effect size for wheat yield using linear mixed models. We found the highest explanatory power during the stem elongation and booting phase under moderate drought stress and during the reproductive phase under moderate heat stress. Furthermore, we observed the highest average yield losses due to moderate and extreme heat stress during the reproductive phase. The highest heat and drought stress-induced yield losses were observed in Brandenburg, Saxony-Anhalt, and northern Bavaria, while similar heat and drought stresses cause much lower yield losses in other regions of Germany.