In the upper U.S. Midwest, oat is a promising crop for diversifying local cropping systems and providing local consumers with a healthy food option. However, as a result of climate change, the crop is facing increasingly severe episodes of high temperature (HT) stress during reproductive development, which limit its yield potential. The goal of this 3-year field study was to identify locally-adapted HT stress-tolerant oat breeding lines, propose a parsimonious mechanistic basis for HT stress tolerance and leverage it to develop a screening method with the potential to support a breeding program. Because water supply is rarely limiting in the region, we tested the hypothesis that canopy latent cooling would be a desirable trait. To this end, we deployed “heat tents” on a core panel of 30 oat lines between booting and heading, where we measured i) grain yield and quality traits (protein, oil and beta-glucan), ii) pollen viability, percentage of filled florets, and grain number, iii) gas exchange and canopy cooling parameters (e.g., photosynthesis, transpiration rate, stomatal conductance, canopy temperature depression). Additionally, we developed a thermal imaging approach to remotely quantify canopy temperature on contrasted lines. Significant genotypic variability was detected in yield and quality trait responses to the HT stress and a physiological path model identified canopy cooling as a main process explaining superior yield performance of HT stress tolerant lines. Interestingly, pollen viability was not found to be the main driver of yield declines, suggesting a role played by other reproductive processes, including those underlying female tissue/organs sensitivity to HT stress. Finally, canopy cooling parameters correlated with geographic locations of breeding programs from which the tested germplasm originated, indicating that they are under selection. Overall, this study opens the way for a breeding program targeting the development of more climate-resilient oats adapted to northern climates.

在美国中西部的上游地区，燕麦是一种很有前景的作物，可以使当地种植系统多样化，并为当地消费者提供健康的食品选择。然而，由于气候变化，作物在生殖发育过程中面临越来越严重的高温 (HT) 胁迫，这限制了其产量潜力。这项为期 3 年的实地研究的目标是确定适应当地的 HT 抗逆燕麦育种品系，提出 HT 抗逆性的简约机制基础，并利用它开发一种有可能支持育种计划的筛选方法。由于该地区的供水很少受到限制，我们测试了树冠潜在冷却将是一个理想特征的假设。为此，我们在引导和航向之间的 30 条燕麦线的核心板上部署了“热帐篷”，我们测量了 i) 谷物产量和品质性状（蛋白质、油和 β-葡聚糖），ii) 花粉活力、饱满小花的百分比和粒数，iii) 气体交换和冠层冷却参数（例如，光合作用、蒸腾速率、气孔导度，冠层温度降低）。此外，我们开发了一种热成像方法来远程量化对比线上的冠层温度。在对 HT 胁迫的产量和质量性状反应中检测到显着的基因型变异性，并且生理路径模型确定冠层冷却是解释 HT 胁迫耐受品系优异产量性能的主要过程。有趣的是，没有发现花粉活力是产量下降的主要驱动因素，这表明其他生殖过程也发挥了作用，包括那些潜在的女性组织/器官对 HT 压力的敏感性。最后，冠层冷却参数与受试种质起源的育种计划的地理位置相关，表明它们正在选择中。总体而言，这项研究为育种计划开辟了道路，该计划旨在开发适应北方气候的更具气候适应性的燕麦。