Traits and the associated loci in wheat favoring extreme high temperature tolerance

Extreme temperature, especially heat stress, is increasingly limiting wheat production, resulting in a large yield loss worldwide. Identifying the cultivars, traits and molecular mechanisms conferring extreme high temperature tolerance is essential for comprehending crop resilience to extreme climates and breeding climate-resilient cultivars. Here, we identified 23 extreme high temperature-tolerant cultivars (11.0%) out of 209 wheat culti-vars based on mass field experiments. In an extreme high temperature year, wheat grain yield was significantly reduced by 27.1% among all the genotypes. We found that radiation use efficiency, plant height, thousand-grain weight, flag leaf width, accumulated thermal time to flowering, net photosynthetic rate and SPAD at flowering and grain filling rate could be the traits associated with extreme high temperature tolerance. These traits were indicative of yield in two years differing in temperature, exhibiting a high heritability. Additionally, 203 loci associated with these traits were identified. The results indicated that the interval 755.97-767.82 Mb on chro-mosome 2 A was linked to flag leaf area, grain yield, accumulated thermal time to flowering and maturity, leaf dry weight at flowering and spike dry weight at flowering, resulting in a cumulative genetic effect on yield. Our findings identify wheat cultivars, traits and associated loci for extreme high temperature tolerance selection, facilitating marker-assisted breeding of cultivars under a changing climate.