The impact of high temperature and drought stress on the yield of major staple crops in northern China

Assessing ozone pollution and climate change impacts on winter wheat: flux modeling vs. dose-response modeling

Surface ozone is a phytotoxic pollutant that damages photosynthetic systems, reduces gas exchange, retards vegetation growth, and decreases yield. In this study, we developed a new ozone flux module within an agroecosystem model framework to enhance our ability to understand, measure, and predict the impact of surface ozone on agricultural productivity. The new module was calibrated and evaluated against historical observational data from multiple sites. It was then applied to predict winter wheat yield and gross primary productivity (GPP) in response to future ozone changes under different climate scenarios. The new ozone flux model was more sensitive to ozone concentration changes than the ozone dose-response model, demonstrating greater GPP and yield losses at the same ozone pollution level. We also investigated several key environmental factors (temperature, precipitation, carbon dioxide) and their synergistic effects with and without ozone to explore the complexity of ozone pollution impacts under climate change. The simulation results indicate a worsening food crisis, driven by interannual trends in crop losses from ozone pollution under high- and moderate-emission scenarios. A more accurate understanding and qualification of ozone's effects on crop growth and yield is essential for safeguarding food security.

Genome-wide identification and characterization of CsHSP60 gene family associated with heat and drought responses in tea plants (Camellia sinensis)

Heat and drought are the stressors with significant adverse impacts on the yield stability of tea plants. The heat shock proteins 60 (HSP60s) play important roles in protecting plants under heat stress. However, the mechanism of HSP60s under heat and drought stresses remains unclear. Here, we identified 19 CsHSP60s (namely CsHSP60-1 to CsHSP60-19) in tea plants and classified them into three groups based on phylogenetic analysis. In addition, studies on gene duplication events during the evolutionary process demonstrated that CsHSP60 members were subjected to purify selection. Analysis of cis-acting elements revealed the presence of numerous stress and hormone-responsive elements within the promoter regions of CsHSP60s. Real-time quantitative fluorescent PCR (qRT-PCR) analyses demonstrated that CsHSP60s rapidly responded to heat and combined heat and drought stress while exhibiting a delayed response to drought stress. The inhibition of eight CsHSP60 genes via antisense oligodeoxynucleotide (AsODN) resulted in more severe damage and ROS accumulation. Specifically, CsHSP60-9, CsHSP60-16, and CsHSP60-19 exhibited notable reductions in Fv/Fm values and displayed increased accumulation of H2O2 and O2·-. These observations indicated a potential role for CsHSP60 in mitigating ROS accumulation under stress conditions, thereby enhancing tea plants' resilience to heat and drought stresses. Using a yeast two-hybrid (Y2H) assay, we identified that CsHSP60-2 and CsHSP60-16 physically interact with CsCPN10-4 and CsCPN10-5, respectively. These interactions suggest a cooperative chaperone activity between CsHSP60 and CsCPN10 in response to combined heat and drought stress. These findings lay a foundation for further understanding the involvement of HSP60s in the tolerance mechanisms to compound heat and drought stresses.

Exogenous melatonin enhances heat tolerance in buckwheat seedlings by modulating physiological response mechanisms

Melatonin (MT) serves as a potent antioxidant in plant organisms, bolstering their resilience to temperature stress. In this study, the impact of MT on various buckwheat varieties under high-temperature stress conditions (40 °C) was investigated. Specifically, five buckwheat seedling varieties, comprising three sweet buckwheat variants (Fagopyrum esculentum) and two bitter buckwheat types (Fagopyrum tataricum), were subjected to foliar sprays of melatonin at concentrations of 50, 100 and 200 μM, with water at 25 °C employed as a control. Results demonstrated that exogenous MT at different concentrations improved the growth and physiological parameters of buckwheats, ameliorating damage induced by high-temperature stress. Notably, the application of 100 μM MT significantly augmented shoot biomasses of buckwheat seedlings under high-temperature conditions. Furthermore, the MT significantly increased the levels of osmotic adjustment substances and chlorophyll concentrations, enhanced antioxidant enzyme activities, chlorophyll fluorescence parameters, and improved photosynthetic gas exchange parameters in five different varieties of buckwheat. This led to the alleviation of damage to buckwheat seedlings subjected to high-temperature stress. Subsequently, five advanced statistical analysis methods: Principal Component Analysis, Grey Relational Analysis, Path Coefficient Analysis, Membership Function Method, and Coupling Coordination Analysis were employed to delve deeper into the existing data indicators. To summarize, the beneficial effect of exogenous melatonin on seedling growth is primarily achieved through the coordination and regulation of the antioxidant enzyme system and osmotic regulatory substances, ensuring the growth and development of buckwheat seedlings while also improving their heat tolerance. The treatment with a concentration of 100 μM of MT was the most effective.

Enhancing Tolerance to Combined Heat and Drought Stress in Cool-Season Grain Legumes: Mechanisms, Genetic Insights, and Future Directions

The increasing frequency of concurrent heat and drought stress poses a significant challenge to agricultural productivity, particularly for cool-season grain legumes, including broad bean (Vicia Faba L.), lupin (Lupinus spp.), lentil (Lens culinaris Medik), chickpea (Cicer arietinum L.), grasspea (Lathyrus sativus L.), pea (Pisum sativum L.), and common vetch (Vicia sativa L.). These legumes play a vital role in sustainable agricultural systems due to their nitrogen-fixing ability and high nutritional value. This review synthesizes current knowledge of the impacts and tolerance mechanisms associated with combined heat and drought stresses in these crops. We evaluate physiological and biochemical responses to combined heat and drought stress, focusing on their detrimental effects on growth, development, and yield. Key genetic and molecular mechanisms, such as the roles of osmolytes, antioxidants, and stress-responsive genes, are explored. We also discuss the intricate interplay between heat and drought stress signaling pathways, including the involvement of Ca2+ ions, reactive oxygen species, transcription factor DREB2A, and the endoplasmic reticulum in mediating stress responses. This comprehensive analysis offers new insights into developing resilient legume varieties to enhance agricultural sustainability under climate change. Future research should prioritize integrating omics technologies to unravel plant responses to combined abiotic stresses.

Trigger thresholds and their dynamics of vegetation production loss under different atmospheric and soil drought conditions

Many evidences have shown that both atmospheric and soil droughts can constrain vegetation growth and further threaten its ability to sequester carbon. However, the trigger thresholds of vegetation production loss under different atmospheric and soil drought conditions are still unknown. In this study, we proposed a Copula and Bayesian equations-based framework to investigate trigger thresholds of various vegetation production losses under different atmospheric and soil drought conditions. The trigger thresholds dynamics and their possible causes were also investigated. To achieve this goal, we first simulated the gross primary production, soil moisture, and vapor pressure deficit over China during 1961-2018 using an individual-based, spatially explicit dynamic global vegetation model. The main drivers of the dynamic change in trigger thresholds were then explored by Random Forest model. We found that soil drought caused greater stress on gross primary production loss than atmospheric drought, with a larger impact area and higher probability of damage. In terms of spatial distribution, the risk probability of gross primary production loss was higher in eastern China than in western China, and the drought trigger threshold was also smaller in eastern China. In addition, the trigger thresholds for atmospheric and soil drought in most regions exhibited a decreasing trend from 1961 to 2018, while the CO2 fertilization enhanced the drought tolerance of vegetation. The reduction in CO2 fertilization effect slowed down the downward trend of trigger threshold for soil drought, while the increase in temperature exacerbated the downward trend of trigger threshold for atmospheric drought. This study highlighted the larger effect of soil drought on vegetation production loss than atmospheric drought and implied that climate change can modulate the trigger threshold of vegetation production losses under drought conditions. These findings provide scientific guidance for managing the increasing risk of drought on vegetation and optimizing watershed water allocation.

Spatio-temporal change of winter wheat yield and its quantitative responses to compound frost-dry events - An example of the Huang-Huai-Hai Plain of China from 2001 to 2020

Extreme climate events such as frost and drought have great influence on wheat growth and yield. Understanding the effects of frost, drought and compound frost-dry events on wheat growth and yield is of great significance for ensuring national food security. In this study, wheat yield prediction model (SCYMvp) was developed by combining crop growth model (CGM), satellite images and meteorological variables. Wheat yield maps in the Huang-Huai-Hai Plain (HHHP) during 2001-2020 were generated using SCYMvp model. Meanwhile, accumulative frost days (AFD), accumulative dry days (ADD) and accumulative frost-dry days (AFDD) in different growth periods of wheat were calculated, and the effects of frost and drought on wheat yield were quantified by the first difference method and linear mixed model. The results showed that wheat yield increased significantly, while the rising trend was obvious at more than half of the regions. Extreme climate events (ECEs) showed a relatively stable change trend, although the change trend was significant only in a few areas. Compared with frost and drought in the early growth period, ECEs in the middle growth period (spring ECEs) had more negative effects on wheat growth and yield. Wheat yield was negatively correlated with spring ECEs, and yield loss was between 4.6 and 49.8 kg/ha for each 1 d increase of spring ECEs. The effects of spring ECEs on wheat yield were ranked as AFDD > AFD > ADD. The negative effect of ADD on wheat yield in the late growth period was higher than that in the other periods. The negative effects of spring ECEs on yield in southern regions were higher than those in northern regions. Overall, due to the adverse effects of frost and drought on wheat yield in the middle and late growth periods, the mean annual yield loss was 6.4 %, among which spring AFD caused the greatest loss to wheat yield (3.1 %). The results have important guiding significance for formulating climate adaptation management strategies.

GDSL Lipase Gene HTA1 Negatively Regulates Heat Tolerance in Rice Seedlings by Regulating Reactive Oxygen Species Accumulation

High temperature is a significant environmental stress that limits plant growth and agricultural productivity. GDSL lipase is a hydrolytic enzyme with a conserved GDSL sequence at the N-terminus, which has various biological functions, such as participating in plant growth, development, lipid metabolism, and stress resistance. However, little is known about the function of the GDSL lipase gene in the heat tolerance of rice. Here, we characterized a lipase family protein coding gene HTA1, which was significantly induced by high temperature in rice. Rice seedlings in which the mutant hta1 was knocked out showed enhanced heat tolerance, whereas the overexpressing HTA1 showed more sensitivity to heat stress. Under heat stress, hta1 could reduce plant membrane damage and reactive oxygen species (ROS) levels and elevate the activity of antioxidant enzymes. Moreover, real-time quantitative PCR (RT-qPCR) analysis showed that mutant hta1 significantly activated gene expression in antioxidant enzymes, heat response, and defense. In conclusion, our results suggest that HTA1 negatively regulates heat stress tolerance by modulating the ROS accumulation and the expression of heat-responsive and defense-related genes in rice seedlings. This research will provide a valuable resource for utilizing HTA1 to improve crop heat tolerance.

Predicting environmental impacts of smallholder wheat production by coupling life cycle assessment and machine learning

Wheat grain production is a vital component of the food supply produced by smallholder farms but faces significant threats from climate change. This study evaluated eight environmental impacts of wheat production using life cycle assessment based on survey data from 274 households, then built random forest models with 21 input features to contrast the environmental responses of different farming practices across three shared socioeconomic pathways (SSPs), spanning from 2024 to 2100. The results indicate significant environmental repercussions. Compared to the baseline period of 2018-2020, a similar upward trend in environmental impacts is observed, showing an average annual growth rate of 5.88 % (ranging from 0.45 to 18.56 %) under the sustainable pathway (SSP119) scenario; 5.90 % (ranging from 1.00 to 18.15 %) for the intermediate development pathway (SSP245); and 6.22 % (ranging from 1.16 to 17.74 %) under the rapid economic development pathway (SSP585). Variation in rainfall is identified as the primary driving factor of the increased environmental impacts, whereas its relationship with rising temperatures is not significant. The results suggest adopting farming practices as a vital strategy for smallholder farms to mitigate climate change impacts. Emphasizing appropriate fertilizer application and straw recycling can significantly reduce the environmental footprint of wheat production. Standardized fertilization could reduce the environmental impact index by 11.10 to 47.83 %, while straw recycling might decrease respiratory inorganics and photochemical oxidant formation potential by over 40 %. Combined, these approaches could lower the impact index by 12.31 to 63.38 %. The findings highlight the importance of adopting enhanced farming practices within smallholder farming systems in the context of climate change. SPOTLIGHTS.

Genetic diversity of durum wheat (Triticum turgidum ssp. durum) to mitigate abiotic stress: Drought, heat, and their combination

Drought and heat are the main abiotic constraints affecting durum wheat production. This study aimed to screen for tolerance to drought, heat, and combined stresses in durum wheat, at the juvenile stage under controlled conditions. Five durum wheat genotypes, including four landraces and one improved genotype, were used to test their tolerance to abiotic stress. After 15 days of growing, treatments were applied as three drought levels (100, 50, and 25% field capacity (FC)), three heat stress levels (24, 30, and 35°C), and three combined treatments (100% FC at 24°C, 50% FC at 30°C and 25% FC at 35°C). The screening was performed using a set of morpho-physiological, and biochemical traits. The results showed that the tested stresses significantly affect all measured parameters. The dry matter content (DM) decreased by 37.1% under heat stress (35°C), by 37.3% under severe drought stress (25% FC), and by 53.2% under severe combined stress (25% FC at 35°C). Correlation analyses of drought and heat stress confirmed that aerial part length, dry matter content, hydrogen peroxide content, catalase, and Glutathione peroxidase activities could be efficient screening criteria for both stresses. The principal component analysis (PCA) showed that only the landrace Aouija tolerated the three studied stresses, while Biskri and Hedhba genotypes were tolerant to drought and heat stresses and showed the same sensitivity under combined stress. Nevertheless, improved genotype Karim and the landrace Hmira were the most affected genotypes by drought, against a minimum growth for the Hmira genotype under heat stress. The results showed that combined drought and heat stresses had a more pronounced impact than simple effects. In addition, the tolerance of durum wheat to drought and heat stresses involves several adjustments of morpho-physiological and biochemical responses, which are proportional to the stress intensity.

Morpho-Anatomical, Physiological and Biochemical Adjustments in Response to Heat and Drought Co-Stress in Winter Barley

This study aimed to investigate the combined effect of high temperatures 10 °C above the optimum and water withholding during microgametogenesis on vegetative processes and determine the response of winter barley genotypes with contrasting tolerance. For this purpose, two barley varieties were analyzed to compare the effect of heat and drought co-stress on their phenology, morpho-anatomy, physiological and biochemical responses and yield constituents. Genotypic variation was observed in response to heat and drought co-stress, which was attributed to differences in anatomy, ultrastructure and physiological and metabolic processes. The co-stress-induced reduction in relative water content, total soluble protein and carbohydrate contents, photosynthetic pigment contents and photosynthetic efficiency of the sensitive Spinner variety was significantly greater than the tolerant Lambada genotype. Based on these observations, it has been concluded that the heat-and-drought stress-tolerance of the Lambada variety is related to the lower initial chlorophyll content of the leaves, the relative resistance of photosynthetic pigments towards stress-triggered degradation, retained photosynthetic parameters and better-preserved leaf ultrastructure. Understanding the key factors underlying heat and drought co-stress tolerance in barley may enable breeders to create barley varieties with improved yield stability under a changing climate.

Field Evaluation of Wheat Varieties Using Canopy Temperature Depression in Three Different Climatic Growing Seasons

During the breeding progress, screening excellent wheat varieties and lines takes lots of labor and time. Moreover, different climatic conditions will bring more complex and unpredictable situations. Therefore, the selection efficiency needs to be improved by applying the proper selection index. This study evaluates the capability of CTD as an index for evaluating wheat germplasm in field conditions and proposes a strategy for the proper and efficient application of CTD as an index in breeding programs. In this study, 186 bread wheat varieties were grown in the field and evaluated for three continuous years with varied climatic conditions: normal, spring freezing, and early drought climatic conditions. The CTD and photosynthetic parameters were investigated at three key growth stages, canopy structural traits at the early grain filling stage, and yield traits at maturity. The variations in CTD among varieties were the highest in normal conditions and lowest in spring freezing conditions. CTD at the three growing stages was significantly and positively correlated for each growing season, and CTD at the middle grain filling stage was most significantly correlated across the three growing seasons, suggesting that CTD at the middle grain filling stage might be more important for evaluation. CTD was greatly affected by photosynthetic and canopy structural traits, which varied in different climatic conditions. Plant height, peduncle length, and the distance of the flag leaf to the spike were negatively correlated with CTD at the middle grain filling stage in both normal and drought conditions but positively correlated with CTD at the three stages in spring freezing conditions. Flag leaf length was positively correlated with CTD at the three stages in normal conditions but negatively correlated with CTD at the heading and middle grain filling stages in spring freezing conditions. Further analysis showed that CTD could be an index for evaluating the photosynthetic and yield traits of wheat germplasm in different environments, with varied characteristics in different climatic conditions. In normal conditions, the varieties with higher CTDs at the early filling stage had higher photosynthetic capacities and higher yields; in drought conditions, the varieties with high CTDs had better photosynthetic capacities, but those with moderate CTD had higher yield, while in spring freezing conditions, there were no differences in yield and biomass among the CTD groups. In sum, CTD could be used as an index to screen wheat varieties in specific climatic conditions, especially in normal and drought conditions, for photosynthetic parameters and some yield traits.