Differences in leaf stomatal traits in an elite double haploid bread wheat population associated with tolerance to drought stress and yield stability

Stomata are microscopic structures on the surface of plant leaves that contribute significantly to photosynthetic efficiency and water loss. Between 2014 and 2017, physiological traits were studied in a doubled haploid (DH) bread wheat population derived from Carberry/AC Cadillac, under rainfed and irrigated conditions, to determine drought tolerance mechanisms and relationship with grain yield. Principal component analysis of grain yield under different growing environments (4 years and 2 water regimes per year) explained over 92% of variance to the first five principal components (PCs), 69% of variance to the first two PCs, and 54% of variance to the first PC, with irrigated environments as the main contributors. Notable wheat lines with consistently higher grain yield were B0767&AG075 (registered as AAC Goodwin), B0767&AX125 and B0767&BF109. Data collected with leaf porometer on flag leaves of wheat lines with contrasting grain yields reveal lower stomatal conductance in these three accessions under water stress. Normalized difference vegetation index and chlorophyll measurements also differed among genotypes suggesting for a possible relationship with grain yield. Results indicate that altering stomatal conductance and density through physiological breeding could improve drought tolerance in wheat. Since the majority of water loss from plants occurs via transpiration through leaf stomata, selecting traits such as stomatal number and size per unit area to limit transpiration rate could provide opportunity to grow wheat in dry environments without grain yield penalty. Physiological understanding of stomatal numbers and function in wheat will be a focus of future studies targeting yield stability under drought stress.