Genotype identification for a water saving trait: Exploring early stomatal closure under soil drying among mid‐South soybean

Abstract

AbstractIt is necessary to understand the differences in physiological responses to water deficit stress of soybean [Glycine max (L.) Merr.] genotypes in order to breed for drought‐tolerant soybean genotypes better suited to water‐limited environments in the U.S. mid‐South region. Using controlled environment and field trials, this study identified soybean genotypes that conserve water through differences in their stomatal response under soil water deficit to determine if this trait confers a yield advantage. Research was conducted from 2017 to 2020 at the West Tennessee Research and Education Center in Jackson, TN. Seventeen mid‐South soybean genotypes (i.e., both, breeding lines and modern commercial soybean) were investigated for an early stomatal closure trait during progressive soil drying under controlled environment conditions. Under field conditions, portable rainout shelters installed when the plant canopies of most genotypes had reached at least 80% canopy closure to impose water deficit stress to nine selected genotypes for field observation of wilting score (WS) and early stomatal closure. Differences were observed among genotypes in their early stomatal closure thresholds with progressive soil drying in the controlled environment. The range in fraction of transpirable soil water (FTSW) thresholds among 17 tested genotypes was 0.33–0.76. Based on our experimental approaches in 4 yr of field studies, genotypes Ellis and USG Allen consistently expressed an early decrease in transpiration rate with progressive soil drying, delayed wilting in the field when soil water deficit developed under rainout shelters, and greater yield when grown in simulated drought conditions.