Genotypic variations in flag leaf- and ear-related traits at pre-anthesis in wheat exposed to mild water deficit under elevated CO2 and high temperatures and their association with grain yield and quality

Global climate change poses a threat to wheat grain yield and quality with the potential to undermine worldwide food security. This study aimed to assess how mild water deficit beginning at the vegetative stage affected morphophysiological and biochemical traits of flag leaves and ears, and subsequently grain yield and quality traits, in two bread (hexaploid) and one durum (tetraploid) wheats grown under elevated CO 2 and high temperatures. A total of 81 continuous variables were measured from flag leaves and ears at ear emergence and grains at maturity. Supervised statistical multivariate analysis showed that flag leaves and ears responded differently to the wheat genotype × water treatment interaction, while grain yield and quality maintained a strong co-structure. Leaf water content decreased in bread wheats, while ear water content only showed a declining trend in durum wheat. The three genotypes reduced leaf nitrogen balance index and productive tillers, while keeping steady WUE. Leaf photosynthesis remained largely unaffected, and ears exhibited less pronounced changes in the antioxidant system than flag leaves. Grain yield decreased in the three wheats, but the grain yield per ear remained. Grain quality traits exhibited high variability. Nitrogen increased in bread wheats, but sulphur trended down in all wheats. Shifts in iron were genotype-dependent, while zinc showed reduced variability. The durum wheat retained better grain quality except for Fe, but it was the least productive. Supervised multivariate analyses effectively uncovered associations between organ traits and wheat genotypes with valuable grain yield and quality traits under global climate change scenarios.