Occurrence of Stem Canker and Tuber Rot on Yam Caused by Rhizoctonia solani AG 2-2IIIB in Korea

摘要

Stem canker and tuber rot symptoms were observed on yam grown in Andong and Jinju, Korea in 2011. A total of 20 isolates of Rhizoctonia and allied fungi were obtained from the symptomatic plants. Among the isolates, 8 isolates were identified as Rhizoctonia solani and 12 isolates as Ceratobasidium sp. based on rDNA-internal transcribed spacer (ITS) sequence similarity. In the cluster analysis of rDNA-ITS sequences, 7 isolates of R. solani belonged to AG 2-2DTB and remaining one to AG 1-1 A. In addition, among the 12 isolates of Ceratobasidium sp., 7 isolates belonged to AG-Fa, three isolates to AG-A and the other two isolates to AG-Fb and AG-O, respectively. Pathogenicity tests showed that all the R solani AG 2-2HTB isolates are pathogenic on stem and tuber of yam but R solani AG 1-1A and all the Ceratobasidium isolates are non-pathogenic. The results indicate that it solani AG 2-2IQB is an important pathogen causing stem canker and tuber rot on yams grown in the study areas. This is the first report of R. solani AG 2-2IIIB causing stem canker and tuber rot of yam in Korea.