Genetic Diversity and Impacts of Warming on U.S. Wheat Yields

Climate change poses an increasing threat to global wheat production, yet the role of genetic diversity in shaping crop sensitivity to warming remains underexplored. This study examines varietal, seasonal, and spatial heterogeneity in U.S. winter wheat yield responses to climate stress using over 35,000 variety-by-location observations from multi-environment trials (1962–2022). By linking trial data to high-resolution weather records and applying a linear mixed-effects model, we estimate genotype- and location-specific yield responses to seasonal temperature variation and extremes. Results show that spring heat and fall freezing are key drivers of yield loss, with spring heat alone reducing yields by an average of 13.5% per 10-unit increase in cumulative degree days above 34°C. Although the yield potential is positively associated with the first trial year of a variety, heat tolerance has not shown a corresponding improvement. Simulations suggest that warming beyond +2°C results in steep yield declines, particularly among heat-sensitive cultivars. These findings provide new empirical evidence on the distribution of heat resilience in the wheat gene pool and underscore the need to integrate heat tolerance into future breeding strategies.