Discovery of Germplasm and Genomic Regions to Improve Drought Tolerance in Soybean

Drought stress is a significant issue threatening the agricultural productivity of soybean (Glycine max). Slow canopy wilting and reduced transpiration rate have been used as traits to phenotype soybean plants for drought tolerance. However, the genetic mechanisms governing these strategies are poorly understood. In this study, we attempt to 1) identify soybean germplasm with drought tolerance by phenotyping for drought tolerance related traits in both the growth chamber and field; 2) elucidate genomic regions responsible for these traits using a genome-wide association study approach. A panel of over 200 genetically diverse soybean lines genotyped with 50K SNPs was assembled and phenotyped. Field evaluation of canopy wilting was conducted at two locations (Athens, GA and Salina, KS) over two years after extended periods with little or no rainfall, and several genotypes were identified that had slow wilting across years and locations. Sensitivity of aquaporins can be correlated with drought tolerance related traits and was evaluated in replicated walk-in growth chamber studies by calculating the difference in transpiration response of de-rooted soybean shoots to deionized water and a chemical inhibitor solution (AgNO₃). Genome-wide association scans have identified putative regions responsible for slow canopy wilting and response to the aquaporin inhibitor. Many of these regions matched QTL locations identified in previous studies for slow canopy wilting. The drought tolerant germplasm and genomic regions identified through this research can be used to improve drought tolerance in a soybean breeding program.