High temperature has been a major limiting factor for wheat (Triticum aestivum L.) productivity and will become a significant driver of yield loss as global warming progresses. Many wheat-growing regions worldwide experience terminal heat stress during the grain-filling period, resulting in grain yield reduction. A sustainable solution to mitigate heat stress-induced damage is to develop heat-tolerant cultivars. To achieve this, identifying tolerant lines is essential to incorporate heat stress resilience into commercial varieties. Our working hypothesis was that retaining chlorophyll content during post-flowering heat stress will reduce yield losses. In this study, we evaluated the terminal heat stress tolerance of 254 diverse spring wheat lines from North American and Australian wheat-breeding programs in two independent experiments. The plants were grown in individual pots under controlled environments. Significant genetic variation was observed for the ability to retain post-stress chlorophyll content and yield components. Grain yield per plant and individual grain weight were significantly correlated with chlorophyll content under heat stress. The reduction in grain yield per plant was contributed more by the reduction of the individual grain weight than by the grain number under heat stress. A highly tolerant line, cultivar Otis, retained 79.2% chlorophyll content relative to control, and also recorded 55% greater chlorophyll content than the average of all 254 lines, at the end of 16 d of severe heat stress treatment. Mapping populations are being developed using Otis, with an aim to identify the genetic basis of chlorophyll retention under terminal heat stress. Resilient wheat lines identified with high grain weight under stress will serve as useful resources for abiotic stress breeding programs.

中文翻译：

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开花后热应激对春小麦多样性面板叶绿素含量和产量组成的影响

高温一直是小麦（Triticum aestivum ）的主要限制因素L.) 生产力，随着全球变暖的进展，将成为产量损失的重要驱动因素。全球许多小麦种植区在灌浆期经历了终末热应激，导致粮食减产。减轻热应激引起的损害的可持续解决方案是开发耐热品种。为实现这一目标，识别耐受品系对于将热应激弹性纳入商业品种至关重要。我们的工作假设是，在开花后热应激期间保留叶绿素含量将减少产量损失。在这项研究中，我们在两个独立实验中评估了来自北美和澳大利亚小麦育种计划的 254 种不同春小麦品系的终端热胁迫耐受性。这些植物在受控环境下在单独的盆中生长。对于保留应激后叶绿素含量和产量成分的能力，观察到显着的遗传变异。单株产量和单粒重与热胁迫下的叶绿素含量显着相关。单株籽粒产量的减少更多地是由于单个粒重的减少而不是热胁迫下的粒数。在严重热应激处理的 16 天结束时，一个高度耐受的品种 Otis 相对于对照保留了 79.2% 的叶绿素含量，并且记录的叶绿素含量比所有 254 个品系的平均值高 55%。正在使用 Otis 开发种群绘图，目的是确定在终末热应激下叶绿素保留的遗传基础。