Nitrogen Fixation Drought Tolerance of the Slow-Wilting Soybean PI 471938

To overcome the severe limitation of crop yield that may result from drought, specific plant traits are being explored. Soybean [Glycine max (L.) Merr.] genotypes that express a "slow-wilting" phenotype have been evaluated as sources of useful drought traits. However, the unique physiological characteristic of PI 471938 resulting in slow-wilting progeny and in high-yielding progeny has not been resolved. This study was undertaken to explore the possibility that it may have especially tolerant N fixation activity as soil dries. In fact, greenhouse experiments confirmed this possibility with its N fixation tolerance being among the greatest reported for soybean genotypes. Like other genotypes with N fixation drought tolerance, the accumulation of ureides in its leaves is low compared to a fast-wilting cultivar. Measurements of water status of PI 471938 as compared to the fast-wilting cultivar Benning showed that PI 471938 is able to maintain a greater leaf turgor pressure during soil drying as a result of a lower osmotic potential.