Occurrence of Edible Burdock Black Scurf in Hokkaido and Its Pathogen

Abstract

In 1992, basal petiole rot and root rot of edible burdock were found in three fields in Hokkaido, Japan. Three isolates were obtained from each field. Two and one isolate were identified as Rhizoctonia solani anastomosis group (AG)-2-2 IIIB and AG-2-2 IV, respectively, based on hyphal anastomosis reaction, culture appearance, temperature-dependent growth characteristics, and specific PCR. The originally observed symptoms were reproduced on roots inoculated with the isolates. Edible burdock black scurf caused by R. solani AG-2-2 IIIB has been previously reported in Japan, however, there are no reports of AG-2-2 IV. Therefore, we propose to include it as one of the pathogens of the disease.