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Heat stress, especially during the reproductive stage, has been exacerbated by changing climatic conditions, resulting in reduced seed yield in crops like Indian mustard. In the present study, 154 genotypes of Indian mustard were used to find novel SSR marker-based associations for seed yield and physiological traits by linkage disequilibrium. Extensive phenotyping of 154 genotypes for seed yield and various physiological traits was done for two consecutive years (2020–2021 and 2021–2022) in timely and late-sown environments. Out of 237 SSR markers, a total of 111 polymorphic markers containing 312 alleles were used for analysis. Two different models, i.e., general linear model (GLM) and mixed linear model (MLM), were used to detect the significant marker–trait associations for timely and late-sown environment separately. A total of 12 and 10 MTAs were found to be associated under timely and late-sown conditions with seed yield and physiological traits using MLM model. Out of these promising MTAs identified in the present study, five SSRs were specifically detected only in late-sown environments which meant that these specific genomic regions and QTLs were associated under terminal heat conditions. This is the first report on the identification of marker-trait associations for physiological traits under terminal heat stress conditions. It may be possible to develop the molecular markers for significant SSRs after due validation. The findings contribute to our understanding of the genetic basis of heat tolerance and provide valuable information for breeding programs aiming to improve crop productivity under heat stress conditions. [ABSTRACT FROM AUTHOR]

After the application of Zn–SA–chitosan bionanoconjugates (BNCs), the physio-biochemical responses of two wheat varieties WH-1124 (heat resistant) and WH-542 (heat sensitive) under terminal heat stress(THS) were assessed in the current study. Zn (Zinc) and SA (Salicylic acid) were slowly released by BNCs to maintain nutrient availability for plants.Application of BNCs enhanced wheat production by enhancing seedling emergence, seed vigour index, and cellular redox homeostasis through antioxidant status regulation, enhanced photosynthetic rate, and cellular and osmotic stability which are essential for stress resistance and plant growth. BNCs (0.01–0.16% w/v) administration at booting and anthesis stages fabricated cellular homeostasis by reducing oxidative damage by suppressing malondialdehyde (MDA), and hydrogen peroxide (H2O2) restoring proline, and its metabolizing enzymes in flag leaf. Comparing control plants treated with, BNCs (0.08%) considerably slowed the loss of carotenoid and chlorophyll levels in both wheat cultivars. Furthermore, foliar treatment of BNCs boosted the activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, glutathione reductase, and glutathione peroxidase in both flag leaf and developing grains on exposure of late sown wheat to THS. BNCs (0.08%) not only promoted early maturity but also significantly slowed the plant height reduction from 12.6% in the control group to just 8.7%. Similarly, the reduction in spike length with awns, and grain yield per pot was controlled to just 5.5% from 7.9% in control.Early emergence, vigorous germination, and early flowering by BNCs synergistically helped the wheat plant in mitigating THS and giving better productivity by providing enough time for grain filling. [ABSTRACT FROM AUTHOR]

Genetic variability and characters association studies play a pivotal role in enhancing selection efficiency under stress condition in plants. Therefore, the study was aimed at assessing the impact of terminal heat stress on various morpho-physiological traits and their association in wheat under control and terminal heat stress condition. The experiment was conducted using thirty-five wheat genotypes in a Randomized Complete Block design (RCBD) plots on three different sowing dates to induce terminal heat stress. A range of 11 morpho-physiological parameters were assessed. All of the traits showed significant variations under studied conditions. Estimates of the genotypic and phenotypic coefficients of variation (GCV and PCV) showed that PCV was higher than GCV indicating large environmental influence on the expression of the traits under study. High GCV and PCV were observed in grain per plant and yield per plant in both normal and heat stress conditions. Chlorophyll content, grain per plant and yield per plant showed highest heritability with high genetic advance (GA) under both normal and terminal heat stress condition. According to the results of the path co-efficient analysis, grain per plant had a strong positive connection with grain yield and plant height and days to 50% flowering had a negative correlation with grain yield per plant under both normal and stress condition. Canopy temperature has direct negative effect on yield in stress condition. The identified traits can be used as effective selection criteria under terminal heat stress condition to develop high yielding heat tolerant wheat variety. [Fundam Appl Agric 2024; 9(2.000): 65-71]

Plant Breeders have the critical challenge of increasing the productivity of bread wheat as a result of several environmental challenges particularly terminal heat stress which affects the plant especially at reproductive stage. In the present investigation, the physiological and biochemical responses of 51 advanced breeding lines of bread wheat developed by ICAR-IIWBR, Karnal, India, along with 5 national check varieties (DBW14 and WR544 as tolerant check, whereas HD2967, RAJ3765, and Sonalika as a susceptible check) have been documented. The field experiment was carried out at 'AB' block farm of Bidhan Chandra Krishi Viswavidyalaya (BCKV), Kalyani, West Bengal, India, in three consecutive years during rabi season from 2017–2018 to 2019–2020. The expression of two stress-associated genes viz., HSP90 and WRKY72a were also assessed under terminal heat stress in selected superior lines concerning physico-biochemical responses. Reduction in relative water content (17.94%), chlorophyll content (0.16%), membrane stability index (6.62%) and pollen viability (7.5%), whereas increases in proline (77.64%) and Malondialdehyde content (2.49%) were observed due to exposure to terminal heat. A significant increase in expression profiling (~ 1.45-fold increase in HSP90 gene and ~ 1.6-fold of WRKY72a) was observed in all selected terminal heat-tolerant genotypes. Based on the clustering pattern with tolerant check, as well as considering the heat susceptibility index (HSI < 0.5) 7 breeding lines viz., NEST17.15, NEST17.26, NEST17.17, NEST17.35, NEST17.14, NEST17.43, NEST17.22 were identified as the potent terminal heat-tolerant lines which could be utilized for developing wheat varieties to combat with forthcoming climate vagaries. [ABSTRACT FROM AUTHOR]

Calcium-dependent protein kinase (CDPK) is member of one of the most important signalling cascades operating inside the plant system due to its peculiar role as thermo-sensor. Here, we identified 28 full length putative CDPKs from wheat designated as TaCDPK (1-28). Based on digital gene expression, we cloned full length TaCPK-1 gene of 1691 nucleotides with open reading frame (ORF) of 548 amino acids (accession number OP125853). The expression of TaCPK-1 was observed maximum (3.1-fold) in leaf of wheat cv. HD2985 (thermotolerant) under T2 (38 ± 3 °C, 2 h), as compared to control. A positive correlation was observed between the expression of TaCPK-1 and other stress-associated genes (MAPK6, CDPK4, HSFA6e, HSF3, HSP17, HSP70, SOD and CAT) involved in thermotolerance. Global protein kinase assay showed maximum activity in leaves, as compared to root, stem and spike under heat stress. Immunoblot analysis showed abundance of CDPK protein in wheat cv. HD2985 (thermotolerant) in response to T2 (38 ± 3 °C, 2 h), as compared to HD2329 (thermosusceptible). Calcium ion (Ca2+), being inducer of CDPK, showed strong Ca-signature in the leaf tissue (Ca—622 ppm) of thermotolerant wheat cv. under heat stress, whereas it was minimum (Ca—201 ppm) in spike tissue. We observed significant variations in the ionome of wheat under HS. To conclude, TaCPK-1 plays important role in triggering signaling network and in modulation of HS-tolerance in wheat. [ABSTRACT FROM AUTHOR]

This research paper investigates the variability in seed oil content (SOC) in Indian mustard (Brassica juncea L.) under terminal heat stress (THS) conditions. A genetic stock of 488 genotypes of B. juncea was evaluated over two years and grouped into five classes based on the reduction in oil content under THS compared to normal sown crop. Based on heat susceptibility index (HSI), a diverse panel of 96 genotypes was selected and evaluated under THS. Twenty-two heat-tolerant donor genotypes were identified, including introgression lines derived from B. tournefortii, B. carinata and Erucastrum cardaminoides. This study is the first to report on marker–trait associations for SOC in B. juncea under THS using a GWAS approach. Furthermore, candidate genes associated with abiotic stress tolerance and lipid metabolism were identified near the significant SNPs, emphasizing their role in SOC regulation under stress. Notable candidate genes include BjuA003240 (encoding for alcohol-forming fatty acyl-CoA reductase), BjuA003242 (involving in lipid biosynthesis), BjuA003244 (associated with mitochondrial functions and stress tolerance), and BjuA003245 (related to MYB transcription factors regulating lipid biosynthesis). This study provides valuable insights into the genetic basis of SOC variation under THS in B. juncea, highlighting potential breeding targets for improved heat stress resilience in Indian mustard cultivation. [ABSTRACT FROM AUTHOR]

Given the global climate change and frequent episodes of high temperature, globally legume crops including chickpea are receiving serious challenge of yield loss across the globe. Therefore, to sustain chickpea production breeders exploiting existing germplasm resources which can withstand drastically happening and fluctuating abiotic stresses like terminal heat and draught. A wide range of genetic variability for various phenological traits and yield related traits were recorded in 71 chickpea genotypes during normal and late or terminal heat stress sown conditions. The analysis of variance for all the environments revealed highly significant differences among the mean square due to genotypes for all the characters. The range of variation was comparatively wider in late sown condition than in normal sown conditions. The differences between phenotypic and genotypic coefficient of variation (PCV and GCV) were not substantial. High heritability coupled with high/moderate genetic advance expressed as percentage of mean were exhibited by hundred seed weight, seed yield/plant, number of pods/plants, plant height, reproductive phase duration, number of primary branches/plant and days to 50 % flowering under normal as well as late planting. So, these traits can be used as selection indices to improve seed yield in high temperature sown condition as well as timely sown condition. The pooled analysis of variance over dates of sowing (environments) were computed following Eberhart and Russell (1966) model. Genotype x environment interactions was highly significant for most of the characters except no. of primary branches/plant when tested against error mean square. G x E (linear) component was significant and higher than non-linear component for days to 50 % flowering, days to maturity, number of pods/plants, hundred seed weight and seed yield per plant. From the present study, five genotypes viz., ICC 14778, GJG 6, ICC 6579, ICC 8950 and ICC 10945 were highly stable for seed yield across the environments.

Terminal heat during reproductive stages of wheat (Triticum aestivum L.) limits the productivity of the crop. Magnesium (Mg) is an essential macronutrient that is involved in many physiological and biochemical processes to affect photosynthesis and seed weight. The present study comparatively evaluated Mg applied to soil (80 kg MgSO4·7H2O ha−1) and to plant foliage (4% w/v) in improving wheat performance under terminal heat. Wheat crop was grown in two sets of treatments until the booting stage, and then one set of plants was shifted to a glasshouse (±5 °C) at the booting stage to grow until maturity in comparison to control plants kept under ambient warehouse condition. Heat stress reduced the pollen viability while foliar- and soil-applied Mg improved it by 3% and 6% under heat stress, respectively, compared to the control without Mg treatment. The 100-seed weight, spike length, and biological yield reduced by 39%, 19%, and 50% under heat stress; however, foliar and soil application increased 100-seed weight by 45% and 40%, spike length by 8% and 5%, and biological yield by 35% and 25% under heat stress, respectively. Soil Mg showed maximum SPAD chlorophyll values; however, response was statistically similar to that of foliar Mg as compared to the control without Mg supply. Membrane stability decreased (4%) due to heat stress while foliar and soil treatments improved membrane stability by 8% and 5% compared to that of the control, respectively. Thus, Mg application through soil or plant foliage can be an effective way to reduce negative impacts of terminal heat in wheat by improving pollen viability at anthesis and 100-seed weight that was attributed to increased chlorophyll contents during anthesis. [ABSTRACT FROM AUTHOR]

In agriculture, the selection of healthy and vigorous seeds is critical, so seeds must be of high quality. Seed priming is a reliable and commercial strategy for improving seed germination and seedling establishment under stressful conditions, whether biotic or abiotic. Heat stress occurs when temperature rises above a particular point and results in permanent irreversible damage to plants, whereas, heat stress that primarily affects crops during their reproductive or grain-filling stages, is referred as terminal heat stress. The present experiment deals with treating two varieties of wheat (HUW-468: Temperature sensitive and HUW-510: Temperature resistant) using boric acid and borax as priming agents and evaluating their effect on different parameters including biochemical (Hydrogen peroxide, Malondialdehyde, and Proline) and antioxidant parameters (Superoxide dismutase, Catalase, Ascorbate peroxidase, and Glutathione reductase) by sowing them under two different conditions (Timely and Late sown) for evaluating effect of priming agents on heat stress on different days of study. The results obtained indicate that primed seedlings grew better and were more resilient to stress, and this was due in part to lower ROS production, stronger membrane stability, a strong antioxidant defense system, and preservation of a strong and healthy crop stand. [ABSTRACT FROM AUTHOR]

SKP1 (S-phase kinase protein1) is an essential regulatory component of SCF (Skp1-cullin-F-box) E3 ubiquitin ligases involved in maintenance of cellular protein homeostasis through ubiquitin mediated proteasome system (UPS). UPS play a key role in stress response and grain yield. Earlier, we isolated TaSKP1-6B-4, highly induced in flag leaf tissues (Accession No. KJ830759.1) of developing wheat caryopses under heat stress. To further assess the functional role of SKP1, genetic variability analysis was carried out in a panel of 25 contrasting germplasm through extensive phenotyping and transcript profiling of TaSKP1-6B-4 during anthesis under ambient and terminal heat stress (THS) in field experiments for two consecutive years. The analysis of variance revealed significant variations for all the traits studied. Higher H2(%), GCV, PCV, GA and GA% mean observed in tiller number per plant (23.81, 17.65, 5.71, 28, 30.86%) and grain number per head (30.27, 82.79, 60.16, 105.00, 108.64%) under THS over ambient temperature. Higher fold induction of TaSKP1-6B-4 transcripts was recorded in 10 genotypes viz. HD2967 (9.9), IC145456 (6.18) in flag leaf; while C-306 (15.88), RAJ3765 (8.37) in ear head. Allele mining of SKP1-6B-4 showed genotypic sequence variations. Whole genome wide search of SKP1 gene family identified 95 SKP1 genes which were structurally characterized. Grain yield, leaf senescence and other agronomic-morpho-physiological parameters combined with transcript profiling, cvHD2967, was found to be the best positively responsive to THS which by pedigree was not heat tolerant. We report a novel 2 year comprehensive field based analysis on collective genetic variability and SKP1/UPS modulation under a natural environmental setting. The data reveals potential functional role of UPS under THS and tolerant cultivars can be further utilized for clarifying the role of UPS mechanistically at the molecular level and for developing terminal heat stress tolerant wheat. Key messages: Genetic diversity and transcript profiling of heat inducible gene in a field experiment collectively identify terminal heat stress tolerant wheat cultivars and involvement of UPS to tackle climate adversity. [ABSTRACT FROM AUTHOR]

Wheat productivity is severely affected by drought and heat stress conditions worldwide. Currently, stem reserve mobilization (SRM) is receiving increased attention as a trait that can sustain wheat yields under adverse environments. However, the significance of SRM in sustaining wheat yields under drought and heat stress conditions remains uncertain in the tropical climate of Indo-Gangetic Plain region. Therefore, this study aimed to investigate genotypic variations in SRM inwheat and their influence on yield sustainability under drought and heat stress environments. The experiment was designed in an alpha-lattice layout, accommodating 43 genotypes under four simulated environments [timely sown and well irrigated (non-stress); timely sown and water-deficit/drought stress; late-sown and wellirrigated crop facing terminally high temperature; and late-sown and water-deficit stress (both water-deficit and heat stress)]. The water-deficit stress significantly increased SRM (16%-68%, p < 0.01) compared to the non-stress environment, while the heat stress conditions reduced SRM (12%-18%). Both SRM and stem reserve mobilization efficiency exhibited positive correlations with grain weight (grain weight spike-1) under all three different stress treatments (p < 0.05). Strong positive correlations between stemweight (at 12 days after anthesis) and grain weight were observed across the environments (p < 0.001); however, a significant positive correlation between stem weight and SRM was observed only with stress treatments. Results revealed that the SRM trait could effectively alleviate the impacts of waterdeficit stress on yields. However, the SRM-mediated yield protection was uncertain under heat stress and combined water-deficit and heat stress treatments, possibly due to sink inefficiencies caused by high temperature during the reproductive period. Defoliated plants exhibited higher SRM than non-defoliated plants, with the highest increment observed in the non-stress treatment compared to all the stress treatments. Results revealed that wider genetic variability exists for the SRM trait, which could be used to improve wheat yield under drought stress conditions. [ABSTRACT FROM AUTHOR]

Climate change has resulted in extreme temperature and drought around the globe, which poses serious threat to food security. Both heat and drought stress affects the production and productivity of wheat crop. The present study was undertaken to evaluate 34 landraces and elite cultivars of Triticum spp. for phenological and yieldrelated traits under optimum, heat, and combined heat–drought stress environments during 2020–2021 and 2021–2022. The pooled analysis of variance showed significant genotype × environment interaction, suggesting an influence of stress on trait expression. The trait performance of genotypes exhibited significant reduction under combined heat–drought stress as compared to optimum and heat stress environments. The maximum seed yield penalty was observed under combined heat–drought stress environment as compared to heat stress alone. Regression analysis indicated significant contribution of number of grains per spike towards stress tolerance. Based on Stress Tolerance Index (STI), genotypes Local-17, PDW 274, HI-8802, and HI-8713 were identified to be tolerant to both heat and combined heat and drought stress at Banda, whereas genotypes DBW 187, HI-8777, Raj 4120, and PDW 274 were tolerant at Jhansi location. The genotype PDW 274 showed stress tolerance under all treatments at both the locations. The genotypes PDW 233 and PDW 291 showed highest stress susceptibility index (SSI) across the environments. The number of grains per spike and test kernel weight were positively associated with seed yield across the environments and locations. The selected genotypes Local-17, HI 8802, and PDW 274 were identified to be the potential sources of heat and combined heat–drought tolerance, which may be utilized in hybridization to develop tolerant wheat genotypes and also for mapping of underlying genes/quantitative trait loci (QTLs). [ABSTRACT FROM AUTHOR]

Wheat productivity is severely affected by drought and heat stress conditions worldwide. Currently, stem reserve mobilization (SRM) is receiving increased attention as a trait that can sustain wheat yields under adverse environments. However, the significance of SRM in sustaining wheat yields under drought and heat stress conditions remains uncertain in the tropical climate of Indo-Gangetic Plain region. Therefore, this study aimed to investigate genotypic variations in SRM in wheat and their influence on yield sustainability under drought and heat stress environments. The experiment was designed in an alpha-lattice layout, accommodating 43 genotypes under four simulated environments [timely sown and well irrigated (non-stress); timely sown and water-deficit/drought stress; late-sown and well-irrigated crop facing terminally high temperature; and late-sown and water-deficit stress (both water-deficit and heat stress)]. The water-deficit stress significantly increased SRM (16%–68%, p < 0.01) compared to the non-stress environment, while the heat stress conditions reduced SRM (12%–18%). Both SRM and stem reserve mobilization efficiency exhibited positive correlations with grain weight (grain weight spike−1) under all three different stress treatments (p < 0.05). Strong positive correlations between stem weight (at 12 days after anthesis) and grain weight were observed across the environments (p < 0.001); however, a significant positive correlation between stem weight and SRM was observed only with stress treatments. Results revealed that the SRM trait could effectively alleviate the impacts of water-deficit stress on yields. However, the SRM-mediated yield protection was uncertain under heat stress and combined water-deficit and heat stress treatments, possibly due to sink inefficiencies caused by high temperature during the reproductive period. Defoliated plants exhibited higher SRM than non-defoliated plants, with the highest increment observed in the non-stress treatment compared to all the stress treatments. Results revealed that wider genetic variability exists for the SRM trait, which could be used to improve wheat yield under drought stress conditions.

Climate change has resulted in extreme temperature and drought around the globe, which poses serious threat to food security. Both heat and drought stress affects the production and productivity of wheat crop. The present study was undertaken to evaluate 34 landraces and elite cultivars of Triticum spp. for phenological and yield-related traits under optimum, heat, and combined heat–drought stress environments during 2020–2021 and 2021–2022. The pooled analysis of variance showed significant genotype × environment interaction, suggesting an influence of stress on trait expression. The trait performance of genotypes exhibited significant reduction under combined heat–drought stress as compared to optimum and heat stress environments. The maximum seed yield penalty was observed under combined heat–drought stress environment as compared to heat stress alone. Regression analysis indicated significant contribution of number of grains per spike towards stress tolerance. Based on Stress Tolerance Index (STI), genotypes Local-17, PDW 274, HI-8802, and HI-8713 were identified to be tolerant to both heat and combined heat and drought stress at Banda, whereas genotypes DBW 187, HI-8777, Raj 4120, and PDW 274 were tolerant at Jhansi location. The genotype PDW 274 showed stress tolerance under all treatments at both the locations. The genotypes PDW 233 and PDW 291 showed highest stress susceptibility index (SSI) across the environments. The number of grains per spike and test kernel weight were positively associated with seed yield across the environments and locations. The selected genotypes Local-17, HI 8802, and PDW 274 were identified to be the potential sources of heat and combined heat–drought tolerance, which may be utilized in hybridization to develop tolerant wheat genotypes and also for mapping of underlying genes/quantitative trait loci (QTLs).

Background: The world's main crop for producing staple foods is wheat. In South Asia's cotton-wheat cropping system, however, a late cotton harvest causes a delayed wheat planting, which causes significant production losses. Therefore, this study investigated genetic diversity among wheat genotypes for late sowing. Additionally, associations between several yield-related parameters were discovered, along with their direct and indirect implications on the choice of the best genotypes suitable for late planting. Methods: Twenty wheat genotypes/advance lines were evaluated under two sowing times, i.e., normal sowing and late sowing for two consecutive years (2019–2021). Data regarding post anthesis traits were collected. Results: The findings showed that planting dates and genotypes substantially (p

In the most productive area of the Indo-Gangetic Plains in Northwest India where high yields of rice and wheat are commonplace, a medium-term cropping system trial was conducted in Haryana State. The goal of the study was to identify integrated management options for further improving productivity and profitability while rationalizing resource use and reducing environmental externalities (i.e., "sustainable intensification", SI) by drawing on the principles of diversification, precision management, and conservation agriculture. Four scenarios were evaluated: Scenario 1 - "business-as-usual" [conventional puddled transplanted rice (PTR) followed by (fb) conventional-till wheat]; Scenario 2 - reduced tillage with opportunistic diversification and precision resource management [PTR fb zero-till (ZT) wheat fb ZT mungbean]; Scenario 3 - ZT for all crops with opportunistic diversification and precision resource management [ZT direct-seeded rice (ZT-DSR) fb ZT wheat fb ZT mungbean]; and Scenario 4 - ZT for all crops with strategic diversification and precision resource management [ZT maize fb ZT wheat fb ZT mungbean]. Results of this five-year study strongly suggest that, compared with business-as-usual practices, SI strategies that incorporate multi-objective yield, economic, and environmental criteria can be more productive when used in these production environments. For Scenarios 2, 3, and 4, system-level increases in productivity (10-17%) and profitability (24-50%) were observed while using less irrigation water (15-71% reduction) and energy (17-47% reduction), leading to 15-30% lower global warming potential (GWP), with the ranges reflecting the implications of specific innovations. Scenario 3, where early wheat sowing was combined with ZT along with no puddling during the rice phase, resulted in a 13% gain in wheat yield compared with Scenario 2. A similar gain in wheat yield was observed in Scenario 4 vis-à-vis Scenario 2. Compared to Scenario 1, wheat yields in Scenarios 3 and 4 were 15-17% higher, whereas, in Scenario 2, yield was either similar in normal years or higher in warmer years. During the rainy (kharif) season, ZT-DSR provided yields similar to or higher than those of PTR in the first three years and lower (11-30%) in Years 4 and 5, a result that provides a note of caution for interpreting technology performance through short-term trials or simply averaging results over several years. The resource use and economic and environmental advantages of DSR were more stable through time, including reductions in irrigation water (22-40%), production cost (11-17%), energy inputs (13-34%), and total GWP (14-32%). The integration of "best practices" in PTR in Scenario 2 resulted in reductions of 24% in irrigation water and 21% in GWP, with a positive impact on yield (0.9 t/ha) and profitability compared to conventional PTR, demonstrating the power of simple management changes to generate improved SI outcomes. When ZT maize was used as a diversification option instead of rice in Scenario 4, reductions in resource use jumped to 82-89% for irrigation water and 49-66% for energy inputs, with 13-40% lower GWP, similar or higher rice equivalent yield, and higher profitability (27-73%) in comparison to the rice-based scenarios. Despite these advantages, maize value chains are not robust in this part of India and public procurement is absent. Results do demonstrate that transformative opportunities exist to break the cycle of stagnating yields and inefficient resource use in the most productive cereal-based cropping systems of South Asia. However, these SI entry points need to be placed in the context of the major drivers of change in the region, including market conditions, risks, and declining labor availability, and matching with the needs and interests of different types of farmers.

Improving terminal heat tolerance is an issue of top priority in wheat breeding in the present era of climate change. Present study was carried out to identify the association among traits of economic importance under terminal heat stress environment. The grain yield/sq. meter under terminal heat stress environment recorded highly significant positive correlation both at genotypic and phenotypic level with grain weight/spike, number of spike/sq. meter, harvest index and 1000-grain weight in both the crop seasons. Path coefficient analysis carried out using genotypic correlation coefficients revealed that days to heading contributing maximum positive direct effect towards grain yield under terminal heat stress environment followed by grain filling duration. Other characters contributing positive direct effects towards grain yield were grain weight/spike, number of spike/sq. meter, harvest index and biological yield/sq. meter under both the crop season. Thus, for improving the wheat grain yield under terminal heat stresses conditions, breeder should aim for selecting genotypes with bold grains or high grain weight /spike, more number of tillers/sq. meter, higher harvest index and longer grain filling duration.

Field pea is highly sensitive to climatic vagaries, particularly high-temperature stress. The crop often experiences terminal heat stress in tropical climates indicating the need for the development of heat-tolerant cultivars. Characterization and identification of stress-adaptive plant traits are pre-requisites for breeding stress-tolerant/adaptive cultivar(s). In the study, a panel of 150 diverse field pea genotypes was tested under three different temperature environments (i.e., normal sowing time or non-heat stress environment (NSTE), 15 days after normal sowing time or heat stress environment-I (LSHTE-I), and 30 days after normal sowing time or heat stress environment-II (LSHTE-II)) to verify the effect of high-temperature environment, genotype, and genotype × environment interaction on different plant traits and to elucidate their significance in heat stress adaptation/tolerance. The delayed sowing had exposed field pea crops to high temperatures during flowering stage by + 3.5 °C and + 8.1 °C in the LSHTE-I and LSHTE-II, respectively. Likewise, the maximum ambient temperature during the grain-filling period was + 3.3 °C and + 6.1 °C higher in the LSHTE-I and LSHTE-II over the NSTE. The grain yield loss with heat stress was 25.8 ± 2.2% in LSHTE-I, and 59.3 ± 1.5% in LSHTE-II compared to the NSTE. Exposure of crops to a high-temperature environment during the flowering stage had a higher impact on grain yield than the heat stress at the grain filling period. Results suggested that the reduced sink capacity (pod set (pod plant−1), seed set (seed pod−1)) was the primary cause of yield loss under the heat stress environments, while, under the NSTE, yield potential was mostly attributed to the source capacity (plant biomass). The high-temperature stress resulted in forced maturity as revealed by shrinkage in crop period (5–11%) and reproductive period (15–36%), prominently in long-duration genotypes. The failure of pod set in the upper nodes and higher ovule abortion (7–16%) was noticed under the high-temperature environments, particularly in the LSHTE-II. Multivariate analysis results revealed seed set, pods plant−1, last pod bearing node, and plant biomass as a critical yield determinant under the heat stress. The GGE biplot suggested that the genotypes G-112, G-114, and G-33 had higher potential to sustain yield coupled with higher stability across the environments and, thus, could serve as a source for breeding heat-tolerant high yielding cultivars. [ABSTRACT FROM AUTHOR]

The reproductive compromise under heat stress is a major obstacle to achieve high grain yield and quality in wheat worldwide. Securing reproductive success is the key solution to sustain wheat productivity by understanding the physiological mechanism and molecular basis in conferring heat tolerance and utilizing the candidate gene resources for breeding. In this study, we examined the performance on both carbon supply source (as leaf photosynthetic rate) and carbon sink intake (as grain yields and quality) in wheat under heat stress varying with timing, duration, and intensity, and we further surveyed physiological processes from source to sink and the associated genetic basis in regulating reproductive thermotolerance; in addition, we summarized the quantitative trait loci (QTLs) and genes identified for heat stress tolerance associated with reproductive stages. Discovery of novel genes for thermotolerance is made more efficient via the combination of transcriptomics, proteomics, metabolomics, and phenomics. Gene editing of specific genes for novel varieties governing heat tolerance is also discussed. [ABSTRACT FROM AUTHOR]

The reproductive compromise under heat stress is a major obstacle to achieve high grain yield and quality in wheat worldwide. Securing reproductive success is the key solution to sustain wheat productivity by understanding the physiological mechanism and molecular basis in conferring heat tolerance and utilizing the candidate gene resources for breeding. In this study, we examined the performance on both carbon supply source (as leaf photosynthetic rate) and carbon sink intake (as grain yields and quality) in wheat under heat stress varying with timing, duration, and intensity, and we further surveyed physiological processes from source to sink and the associated genetic basis in regulating reproductive thermotolerance; in addition, we summarized the quantitative trait loci (QTLs) and genes identified for heat stress tolerance associated with reproductive stages. Discovery of novel genes for thermotolerance is made more efficient via the combination of transcriptomics, proteomics, metabolomics, and phenomics. Gene editing of specific genes for novel varieties governing heat tolerance is also discussed.

Terminal heat stress severely affects the growth of wheat crop causing drastic reduction in the yield and nutritional quality of the grains. Various technologies have been developed in the past to alleviate the effect of terminal heat stress (HS) in wheat, but with limited success. Silicon (Si), being quasi-essential element, has many beneficial advantages to the plants. Here, we observed exogenous application of 2.5 mM Si to be very effective in modulating the thermo-tolerance and quality of the grains. The application of Si2.5 has been observed to trigger the expression of signalling molecules (MAPK, CDPK), and stress-associated genes (SAGs) like HSFs (HD97, HSFA6e), HSPs (HSP17, HSP23, HSP70 and HSP90) and genes of antioxidant enzyme (GPX and SOD) under HS. Thermo-tolerant wheat cv. HD3086 showed more abundance of SAGs transcripts, as compared to thermo-susceptible cv. BT-Schomburgk. We observed increase in the accumulation of photosynthetic enzyme (RuBisCo activase) in leaves and storage protein (gliadin) in wheat grains under Si2.5 treatment. Heat stress downregulates the expression of genes linked with starch biosynthesis pathway; the percent decrease observed was minimum under Si2.5 treatment. Improved grain quality in both cvs. in response to Si2.5 under HS was observed. Si2.5 inhibits the activity of starch-degrading enzyme in endospermic tissue of grains. Si2.5 application was very effective, cheap and non-hazardous for mitigating the effect of terminal HS in wheat, stabilizing yield without compromising the quality of the grains. [ABSTRACT FROM AUTHOR]

• Terminal heat stress leads to irreversible damage in wheat. • Marker assisted selection and gene pyramiding for portrayal of heat tolerance. • Allelic frequency and polymorphic information showed significant variability. • Markers xcfa2147 and xwmc671 could be potentail for heat stress tolerance. Terminal heat stress causes irreversible damage to wheat crop productivity. It reduces the vegetative growth and flowering period that consequently declines the efficiency to capture available stem reserves (carbohydrates) in grains. Markers associated with thermotolerant traits ease in marker assisted selection (MAS) for crop improvement. It identifies the genomic regions associated with thermotolerant traits in wheat, but the scarcity of markers is the major hindrance in crop improvement. Therefore, 158 wheat genotypes were subjected to genotyping with 165 simple sequence repeat markers dispersed on three genomes (A, B and D). Allelic frequency and polymorphic information content values were highest on genome A (5.34 (14% greater than the lowest value at genome D) and 0.715 (3% greater than the lowest value at genome D)), chromosome 4 (5.40 (16% greater than the lowest value at chromosome 2) and 0.725 (5% greater than the lowest value at chromosome 6)) and marker xgwm44 (13.0 (84% greater than the lowest value at marker xbarc148) and 0.916 (46% greater than the lowest value at marker xbarc148)). Bayesian based population structure discriminated the wheat genotypes into seven groups based on genetic similarity indicating their ancestral origin and geographical ecotype. Linkage disequilibrium pattern had highest significant (P < 0.001) linked loci pairs 732 on genome A at r2 > 0.1 whereas, 58 on genome B at r2 > 0.5. Linkage disequilibrium decay (P < 0.01 and r2 > 0.1) had larger LD block (5–10 cM) on genome A. Highly significant MTAs (P < 0.000061) under heat stress conditions were identified for flag leaf area (xwmc336), spikelet per spike (xwmc553), grains per spike (cxfa2147 , xwmc418 and xwmc121), biomass (xbarc7) and grain yield (xcfa2147 and xwmc671). The identified markers in this study could facilitate in MAS and gene pyramiding against heat stress in wheat. [ABSTRACT FROM AUTHOR]

Understanding the behavior of crops under interactive effect of different abiotic stresses is the need of hour. Present study aimed to examine the interactive effect of late planting and deficit irrigation on wheat (Triticum aestivum L.) growth and development in semi-arid environment. The field experimentation with two planting dates and three levels of irrigation was conducted during rabi 2015-16 and 2016-17. The results showed that response of water stress on wheat growth and development behaved in similar manner as of that in late planting. The reduction in LAI, biomass, yield and yield attributes was observed under independent effect of water stress as well as late planting with varied magnitude. Noticeably, late sowing had large influence on rate of LAI change in the order of 20% and 47% in greening and senescence phase, respectively than deficit irrigation. The slowdown of LAI change in greening phase is also associated with faster senescence in late phase of crop growth. However, the additive effect was observed under combined water deficit and late planting conditions. It may be concluded that the co-existence of limited water availability and late planting is most detrimental to wheat growth and development ultimately on crop yields in semiarid environment. Therefore, suitable agronomic and breeding strategies must be devised to mitigate the hampering effect of combined reduced water availability and late planting conditions.

Among all the abiotic stresses, high temperature stress, especially at flowering, is the major factor causing substantial reduction in cotton yield. To check the effect of foliar applied chitosan (CH), a derivative of chitin, for inducing thermo-tolerance during flowering stage in cotton crop, a field experiment was conducted during 2016 and repeated in 2017. Heat stress was imposed at flowering stage for 4 and 8 days and varied chitosan concentrations (0, 0.2, 0.4, 0.6 and 0.8 g L-1) were applied foliarly after imposing heat stress. Heat was imposed by making the plastic tunnels using perforated transparent polythene sheet. High temperature stress reduced leaf total phenolic contents, total soluble proteins, turgor potential, relative leaf water contents and seed cotton yield. Application of chitosan @ 0.8 g L-1 induced thermo-tolerance by improving all the recorded parameters under high temperature stress while application of chitosan @ 0.6 g L-1 improved the bio-chemical, physiological and yield components under ambient conditions. Conclusively, high temperature stress adversely affected the recorded response while foliar application of high dose of chitosan ameliorated the adverse effects of heat stress at bio-chemical and physiological levels. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the potential of exogenously applied ascorbic acid (AsA) (100, 150 and 200 ppm) as foliar spray at 70 and 90 days after sowing. Matured grains were analyzed for terminal heat stress responses during grain development in six wheat genotypes namely PBW 550, PBW 725 (released), BWL 1664, BWL 3560, BWL 5230 (advanced lines) and Himachal Local 1 (landrace) under late sown conditions. In comparison to control, 150 ppm AsA specifically showed significant upregulation of antioxidant enzymes as peroxidase, catalase, polyphenol oxidase and phenylalanine ammonia lyase in grains along with enhanced non-enzymatic antioxidants such as total polyphenols, phenolic acids, flavonols, anthocyanins and proanthocyanidins. This enhancement in the levels of non-enzymatic antioxidants could be associated with the activation of phenylalanine ammonia lyase enzyme involved in shikimic acid pathway in wheat grains. Contents of osmoprotectants like reducing sugars, sucrose and amino acids were also increased with AsA applied. Advanced lines like BWL showed higher grain yield under the effect of AsA that could be linked to the upregulated enzymatic antioxidants as well as osmoprotectants and secondary metabolites. The results revealed the efficacy of foliar applied AsA in improving the wheat performance under late sown conditions. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinase (MAPK) signaling cascade is highly conserved across the species triggering the self-adjustment of the cells by transmitting the external signals to the nucleus. The cascade consists of MAPK kinase kinases (MAPKKKs), MAPK kinases (MAPKKs) and MAPKs. These kinases are functionally interrelated through activation by sequential phosphorylation. MAPK cascade is involved in modulating the tolerance and regulating the growth and developmental processes in plants through transcriptional programming. The cascade has been well characterized in Arabidopsis, Tobacco and rice, but limited information is available in wheat due to complexity of genome. MAPK-based sensors have been reported to be highly specific for the external or intracellular stimuli activating specific TF, stress-associated genes (SAGs) and stress-associated proteins (SAPs) linked with heat-stress tolerance and other biological functions especially size, number and quality of grains. Even, MAPKs have been reported to influence the activity of ATP-binding cassette (ABC) transporter superfamily involved in stabilizing the quality of the grains under adverse conditions. Wheat has also diverse network of MAPKs involved in transcriptional reprogramming upon sensing the terminal HS and in turn protect the plants. Current review mainly focuses on the role of MAPKs as signaling sensor and modulator of defense mechanism for mitigating the effect of heat on plants with focus on wheat. It also indirectly protects the nutrient depletion from the grains under heat stress. MAPKs, lying at pivotal positions, can be utilized for manipulating the heat-stress response (HSR) of wheat to develop plant for future (P4F). [ABSTRACT FROM AUTHOR]

Wheat sowing often gets delayed and the crop faces terminal heat stress, which is severely impacting the crop productivity. Synthetic osmolytes maintain structural integrity of cell membrane and protect oxidative damage of cells under stress conditions. Hence, foliar application of these compounds is likely to alleviate the negative effects of high temperature on crop plants. However, field response of these chemicals on late-sown wheat in the subtropical environment (eastern Indo–Gangetic Plain) is still uncertain. A field experiment was conducted for three years (2013–2016) to envisage the field efficacy of two synthetic compounds viz., potassium nitrate (KNO3) (1.0 and 0.5%) and glycine betaine (GB) (100 and 50 mM), each sprayed either at respective higher dose at booting or anthesis, or at half the dose at both booting and anthesis for improving grain yield of two contrasting wheat cultivars (DBW14 and K307) facing terminal heat stress. Foliar application of 0.5% KNO3 at both booting and anthesis stages resulted in the maximum increase (13–16%) in grain yield over no-spray treatment closely followed by 1% KNO3 at anthesis (10–14%), and 50 mM GB at both booting and anthesis stages (6–9%). However, foliar spray of KNO3 and GB at only booting stage had a non-significant effect on grain yield. The increase in grain yield with the osmolytes application was attributed to an increase in the number of grains ear− 1 (9–16%) and thousand-grain weight (3–10%), demonstrating an increased sensitivity of sink capacity and grain development of wheat to terminal heat stress. The degradation of flag leaf chlorophyll content (34–36%) and increase in the relative membrane permeability (29–52%) during anthesis to grain filling period was observed as the critical yield-limiting factors in late-sown wheat. Foliar spray of osmolytes had a regulatory effect on these physiological anomalies being highest with the treatment 0.5% KNO3 foliar spray at both booting and anthesis stages followed by 1% KNO3 foliar spray at anthesis. At the grain filling stage, significant relationships between grain yield and flag leaf chlorophyll (r = 0.43–0.68) and relative membrane permeability (r = − 0.47 to − 0.53) were observed. Thus, foliar application of 0.5% KNO3 at both booting and anthesis stages could be recommended to alleviate the adverse effect of terminal heat stress and improve productivity of late-sown wheat in subtropical environments. [ABSTRACT FROM AUTHOR]

In order to evaluate the influence of sowing dates and zinc levels on yield and yield components of wheat (Triticumaestivum L.) in Ahwaz, a split-plot experiment including three sowing dates (29 Nov, 14 and 30 Dec) in main plots and five zinc levels (0 (control), 10, 20, 30 and 40 kg/ha) in sub plots were implemented with three replicates in research farm of Agricultural Sciences and Natural Resources University of Khuzestan, Ahwaz, Iran. The mean comparison of sowing dates showed that the maximum grain yield was related to sowing date of 29 Nov and the minimum was obtained from 30 Dec. The mean comparison of zinc levels showed that the highest grain yield was in 30 kg/ha zinc and the lowest was in 0 kg/ha zinc. The mean comparison of interaction effect showed that the maximum grain yield was produced from 29 Nov and 30 kg/ha zinc and the minimum amount was related to 30 Dec and 0 kg/ha zinc. In general, in all sowing dates, zinc application increased grain yield of wheat.

Breeding for terminal heat stress (THS) in Brassica juncea L. Czern & Coss is recognized as an imperative objective for sustained productivity in contemporary climatic changes. A fixed diversity stock of 491 genotypes was documented for wide range of variations for seed yield under natural terminal heat stress. A set of top 20 genotypes comprising introgression lines from wild species Erucastrum cardaminoides and B. tournefortii; derived B. juncea lines using B. carinata and B. napus; land races;, commercial cultivars and breeding lines, having the lowest heat susceptibility index and the least yield reduction under heat stress, have been identified as potential heat tolerant donors. A panel of 96 genotypes was constituted from this stock on the basis of their differential response to heat susceptibility index and seed yield reduction under natural THS. The constituted panel was evaluated for validation under controlled conditions for ten seed yield-related traits. Moderate to low correlations between SY and its related traits were observed in NS and THS conditions. Double digest restriction site associated DNA sequencing of 71 genotypes identified 18,258 SNPs after filtration. Least square means of all the traits under NS and THS conditions and the best linear unbiased predictors along with identified SNPs were used for genome-wide association study. A total of 34 SNPs under NS, 24SNPs under THS and 30SNPs using BLUP values were found to be associated with all seed yield-related traits. Chromosome B05 harbored the maximum number of SNPs (nine) followed by chromosomes A07 and A09 (eight SNPs each). SNPs under NS conditions could not be associated with THS. This is the first report on the identification of 24 marker-traits associations detected for SY and its component traits under THS conditions. It may be possible to develop the molecular markers for significant SNPs after due validation. The constituted panel may also serve as a source of allelic diversity for genes controlling various economic traits. The derived introgression lines as potential heat tolerant donors indicated the possibility of using wild species to breed for abiotic stress tolerance in Indian mustard. [ABSTRACT FROM AUTHOR]

Terminal heat stress leads to sizeable yield loss in late-sown wheat in tropical environments. Several synthetic compounds are known to counteract plant stress emanating from abiotic factors. A field experiment was conducted in Sabour (eastern India) during 2013–2016 to investigate the field efficacy of two synthetic compounds, calcium chloride (CaCl2) and arginine, for improving grain yield of two contrasting wheat cultivars (DBW 14 and K 307) facing terminal heat stress. For this, foliar spray of 18.0 mM CaCl2 at booting (CCB) or anthesis (CCA), 9.0 mM CaCl2 at both booting and anthesis (CCB+A), 2.5 mM arginine at booting (ARGB) or anthesis (ARGA) and 1.25 mM arginine at both booting and anthesis (ARGB+A) treatments along with no-spray and water-spray treatments were evaluated in late-sown wheat. The highest grain yield was recorded in treatment CCB+A, followed by CCA and ARGB+A. However, the effect of these compounds was marginal on grain yield when applied only at the booting stage. Grains/ear and thousand-grain weight were found to be the critical determinants for yield in late-sown wheat. During the anthesis to grain filling period, flag-leaf chlorophyll degradation and increase in relative permeability in no-spray treatment were 34–36% and 29–52%, respectively, but these values were reduced considerably in CCB+A treatment followed CCA. Thus, foliar spray of 9.0 mM CaCl2 both at booting and anthesis stages may be recommended for alleviating the negative impacts of terminal heat stress in late-sown wheat and improving its productivity (>13%). [ABSTRACT FROM AUTHOR]

Contribution of stem photoassimilates towards grain filling may have significance under stress, since it may force the plant to initiate an early leaf senescence, thereby limiting the availability of flag leaf photosynthates for grain filling. Radiotracer feeding of 14C-sucrose to the internode by stem injection method at 20 days stage after anthesis and measurement of 14C activity in grains at 5 days after foliar application of potassium iodide, meant to inhibit current photosynthesis by inducing leaf senescence, showed a gradual decline in flag leaf chlorophyll but an increase in accumulation of 14C particularly in the basal spikelet grains. However, a reduction in grain filling at all the sink positions within the wheat ear was measured with hastened leaf senescence. On the other hand, abiotic stresses such as high temperature stress, is known to cause an abortion of the basal florets in wheat and induce an early flag leaf senescence. We have earlier shown that seed gamma irradiation, at 0.1 kGy causes an increase in grain mass at middle and basal spikelet positions. In this paper we report that the reduction in grain yield in response to terminal heat stress can be compensated by gamma irradiation, owing to better stem reserve mobilization into the basal and middle spikelet under condition of stress induced senescence. [ABSTRACT FROM AUTHOR]

The present study aimed to reveal the impact of the stay-green trait in bread wheat under terminal heat stress. Field experiments (early and late sowing; for two consecutive years) were conducted to investigate the influence of terminal heat stress on the morpho-physiological traits in different stay-green types i.e., non-stay-green, moderately non-stay-green, moderately stay-green, and stay-green. In addition, the greenhouse experiment was performed to dissect the stay-green trait in functional stay-green, non-functional stay-green, and non-stay-green genotypes. The results of the field experiments confirmed that genotypes exhibiting the stay-green trait have a significantly high chlorophyll content, normalized difference vegetative index, grain yield, biological yield, kernel weight, and low canopy temperature under control and heat stress conditions. In the greenhouse experiment, functional stay-green and non-functional stay-green genotypes showed a high chlorophyll content and photochemical efficiency, whereas biological yield and grain yield showed a significant relation with the functional stay-green genotype under control and terminal heat stress treatments. The sequencing and expression analysis of chlorophyllide a oxygenase (CaO), light-harvesting complex (Cab), stay-green (SGR), and red chlorophyll catabolite reductase (RCCR) in functional stay-green, non-functional stay-green, and non-stay-green genotypes revealed variations in the exons of CaO and RCCR; and significant difference in the regulation of CaO and Cab at 7 days after anthesis under terminal heat stress. This study confirms that genotypes displaying the stay-green trait can aid wheat breeders to cope with increasing temperature in the impending decades.

South Asia is the world’s most poverty-dense region, where climate change and climate variability are expected to result in increased heat stress and erratic precipitation patterns that affect agricultural productivity. Considerable evidence has been generated on the effects of these stresses on crop yield, though previous research has not yet examined their influence on the economic efficiency of cereal producers. Surveying 240 farmers across eight of Pakistan’s twelve agro-ecological zones, we examined the impact of temperature and precipitation anomalies – as indicators of climatic variability – and the number of days when temperature exceeds crop specific heat stress thresholds on the economic efficiency of rice and wheat production. To this end, we employed first-stage stochastic production frontier (SPF) models and second-stage ordinary least square (OLS) and quantile regression models. Both OLS and quantile regressions indicated that terminal heat >34 °C has a significant negative impact on wheat production economic efficiency. Small positive deviation (0.54 °C ± 0.16 SD) of the wheat season’s mean temperature from the medium-term historical mean also significantly and negatively affected economic efficiency across all regression models. Heat stress >35.5 °C during rice flowering in the monsoon also had a significant and negative impact. A slight positive deviation in temperature averaging 0.38 °C (±0.11 SD) above the medium-term mean also had significant negative effects across all regressions. Cumulative precipitation conversely had significant yet contrary effects, by offsetting farmers’ investment in supplementary irrigation and increasing economic efficiency. Our results highlight the fact that indicators of climatic variability and heat stress negatively affect the economic efficiency of both rice and wheat producing farmers. Farmers’ education and access to financial and extension services were however both positively associated with economic efficiency. Our findings point to the importance of developing interlinked agronomic, economic and socio-ecological policy strategies to adapt and increase the resilience of Pakistan’s cereal systems to climatic variability. [ABSTRACT FROM AUTHOR]