Soybean Tolerance to Water‐Saturated Soil and Role of Resistance to Phytophthora sojae

There are differences among soybean [Glycine max(L.) Merr.] genotypes for tolerance to water‐saturated soil conditions. Phytophthora root rot caused by Phytophthora sojae(M.J. Kaufmann and J.W. Gerdemann) is problematic for soybean when the soil is excessively wet. Our objectives were (i) to determine if genotype‐by‐environment (G × E) interactions existed for yield between water‐saturated (irrigated) vs. control (nonirrigated) environments using 37 soybean genotypes; and (ii) to determine whether resistance and/or partial resistance to P. sojaewas associated with tolerance to water‐saturated soil conditions. The G × E was significant between the water‐saturated treatment and control. Some genotypes that yielded well under control conditions did not yield well under saturated conditions. Based on yield, we identified eight genotypes that were tolerant and eight genotypes that lacked tolerance to water‐saturated soil conditions. These 16 genotypes were evaluated for resistance and partial resistance to Phytophthora using three virulence phenotypes. Those genotypes that were tolerant to water‐saturated soil conditions possessed either a major gene or good partial resistance to P. sojae. We concluded that resistance to P. sojaewas an important factor that increased tolerance to water‐saturated soil, but that unknown other genetic factors were also important.