北海道の農家圃場で発生したRhizoctonia solani AG-2-2Ⅳによるダイズリゾクトニア根腐病およびR. solani AG-1ⅠB によるアズキリゾクトニア根腐病

抄録

Hypocotyl rot of soybean and adzuki bean were observed in commercial fields of Hokkaido, Japan in June 2008. A Rhizoctonia-like fungus was frequently isolated from diseased portions of the plants. We identified the soybean isolate as Rhizoctonia solani anastomosis group（AG）-2-2Ⅳ and the adzuki bean isolate as R. solani AG-1ⅠB on the basis of cultural appearance, mycelial growth temperature, hyphal anastomosis, and the results of PCR using subgroup-specific primers. Inoculation tests with the isolates revealed that the fungus caused the same symptoms on the original hosts and were reisolated from portions of the host exhibiting the symptoms. We propose R. solani AG-2-2Ⅳas another pathogen of root rot of soybean, because it has not been reported as a pathogen in Japan. This is the first report on adzuki bean root rot caused by R. solani in commercial fields in Japan.