First report of yeast spot caused by Eremothecium coryli on soybean in South Korea

An ascomycete yeast was isolated from tissue cultures of soybean explants (cv. Williams 82) exhibiting blanching and discoloration. Stink bug damage was confirmed in soybean seeds that were grown and harvested simultaneously in the same field as the soybeans used for tissue culture, and the same yeast was isolated from areas of stink bug damage, indicating seed contamination. The seed infection rate was 20%, and all infected seeds had been damaged by stink bugs. The yeast was identified as Eremothecium coryli (Peglion) Kurtzman based on morphological and biochemical characteristics and homology analysis of the internal transcribed spacer sequence of the ribosomal RNA gene and the large ribosomal subunit D1/D2 domain regions. Disease symptoms were reproduced by inoculating this yeast into healthy soybeans (cv. Williams 82). Eremothecium coryli has been reported to cause yeast spot disease in soybeans, but has not been reported in Korea. Among the fungicides recommended for plant tissue culture, we recommend imazalil for addressing E. coryli contamination. The results of this study suggest that yeast spot caused by E. coryli presents a significant risk to soybean production.