Differential Genotypic Response to Drought Stress and Subsoil Aluminum in Soybean

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Abstract
Soybean [Glycine max (L.) Merr.] producers in the southeastern USA are often confronted with the problems of drought and toxic levels of subsoil Al. Our objective in this study was to determine the reaction of diverse soybean genotypes to combined effects of these two stress factors. Greenhouse studies were initiated to examine the problem. Two levels of Al saturation in a subsoil layer (6 and 71%), two levels of soil moisture (watered vs. unwatered),three genotypes (‘Forrest’, breeding line N77‐114, and PI 416937), and three sampling dates were used as treatments. Data were collected during a 14‐d drying cycle imposed at early to midpodfilling. Control pots were watered daily. Traits measured were relative water content, water potential, transpiration, diffusive resistance, leaf weight, and stem weight. In the combined presence of drought and Al stress, the Plant Introduction (PI) maintained a substantially higher relative water content, water potential, transpiration, and leaf weight than Forrest or N77‐114. Under drought stress alone, the water status of the PI was inferior to that of Forrest and N77‐114. These data suggest that Al tolerance can impart drought tolerance when subsoil Al is present. In regions where subsoil Al toxicity and drought are common, breeders should consider Al screening of germplasm to efficiently characterize and develop drought tolerant cultivars.

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