Effect of Heat Stress on Wheat Quality and Its Heterogeneity: A Global Meta-Analysis

Global climate warming poses a serious threat to wheat production. Existing studies have primarily focused on the impact of heat stress on wheat yield, but the effect on its quality remains uncertain, especially at a global scale. To fill this knowledge gap, we conducted a global meta-analysis integrating 1976 observations from 95 peer-reviewed studies, encompassing nine key wheat quality traits. Using a random-effects model, we quantified the overall impact of heat stress and explored its influencing factors. Our results show that, compared with optimal temperature conditions, heat stress significantly reduced two major quality traits, specifically thousand-kernel weight (-12.7%) and starch content (-6.5%), while increasing protein (+7.2%) and wet gluten content (+8.0%). Subgroup analyses revealed consistent quality response trends across different wheat types, albeit with varying magnitudes. Interestingly, wheat varieties with a significantly higher protein content under heat stress often show a smaller decrease in starch content, which highlights the compensatory relationship between carbon and nitrogen metabolism. Among all developmental stages, the grain filling phase was the most sensitive to heat stress, exerting the greatest negative effect on wheat quality. Furthermore, elevated soil potassium levels were found to mitigate some of the adverse effects, emphasizing the potential of nutrient management as an adaptation strategy. These findings elucidated the complex mechanisms of wheat quality changes under heat stress and emphasized the importance of enhancing climate adaptability through strategies such as optimizing sowing dates, potassium fertilizer management, and breeding heat-tolerant varieties, providing a scientific basis for global food security and high-quality wheat production.