Occurrence of Web Blight in Soybean Caused by Rhizoctonia sol ani AG-l(IA) in Korea

Abstract

Web blight symptoms were frequently observed on soybean plants grown in a farmer's fields located in Jincheon in Korea during a disease survey in August, 2005. Incidence of the disease was <TEX>$5-20\%$</TEX> infected plants in two of four soybean fields investigated. A total of 31 isolates of Rhizoctonia sp. were obtained from leaves, leaf petioles, and pods of diseased soybean plants. The isolates were identified as Rhizoctonia solani AG-l(IA) by anastomosis test and based on the morphological and cultural characteristics. Three isolates of R. solani AG-l(IA) were tested for pathogenicity to five cultivars of soybean by artificial inoculation. All the isolates induced blight symptoms on the leaves of soybean and formed sclerotia on the lesions, which were similar to those observed in the field. The pathogenicity tests revealed that all the soybean cultivars tested were susceptible to the pathogen. There was no difference in the pathogenicity among the isolates. The present study first reveals that R. solani AG-l(IA) causes web blight of soybean in Korea.