Damping-off on Wasabi Caused by Rhizoctonia solani AG-2-1·Subset 2 and AG-2-1·clade HK

Abstract

In June 2019, basal petiole rot of wasabi seedlings with withering symptom was observed in Iwate, Japan. Isolates from diseased tissues were identified as Rhizoctonia solani anastomosis group (AG)-2-1·Subset 2 and AG-2-1·clade HK on the basis of cultural morphology, temperature-dependent growth characteristics, hyphal anastomosis reactions, and DNA sequences of the rDNA-ITS region. Artificial inoculation with three isolates resulted in basal petiole rot and withering of wasabi seedlings. The occurrence of damping-off on wasabi caused by R. solani has been reported in Japan (Suzuki, 1976); however, details of AG and locations were not clarified. Since the AGs of R. solani causing this damping-off were initially found in Japan, we propose to the inclusion of R. solani AG-2-1·Subset 2 and AG-2-1·clade HK as one of the pathogens of the disease.