Genome-Wide Association Analysis of Carbon Isotope and Oxygen Isotope Ratio in Diverse Soybean [Glycine max (L.) Merr.] Genotypes.

Drought stress is a major factor limiting soybean [Glycine max (L.) Merr.] yield. High water use efficiency (WUE) contributes to crop productivity under drought, but genotypes with high WUE often have inherently low transpiration which limits crop growth even under optimum conditions. Measurement of genetic variability in WUE and T through carbon isotope ratio (δ^13 C) and oxygen isotope ratio (δ^18 O), respectively, could be important in identifying the genotypes with high WUE that also have relatively high T, and hence, high rate of biomass production.