Basal Stem Rot of Broccoli Caused by Rhizoctonia solani AG-2-1 and AG-4 in Korea

Abstract

Basal stem rot symptoms were frequently observed on broccoli plants grown in farmers' fields located in Gimje and Jeju, Korea during disease surveys carried out in November and December 2019. Incidence of the diseased plants was 1-10% in the fields investigated. Five isolates of Rhizoctonia sp. were obtained from the diseased plants. Of the isolates, two were identified as Rhizoctonia solani AG-2-1 based on the morphological characteristics and anastomosis test, and three were as R. solani AG-4. Two isolates each of R. solani AG-2-1 and AG-4 were tested for pathogenicity on broccoli by artificial inoculation. All the tested isolates induced basal stem rot symptoms on the inoculated plants. The symptoms were similar to those observed in the fields investigated. This is the first report of basal stem rot of broccoli caused by AG-2-1 and AG-4 in Korea.