Rhizoctonia solani AG-2-1·Subset1およびAG-2-2 IVによるブロッコリー生育期の苗立枯症状の発生（病原追加）

抄録

In June 2016, basal stem rot and underdeveloped broccoli growth occurred in two fields in Hokkaido, Japan. Two isolates obtained from diseased broccoli were identified as Rhizoctonia solani (anastomosis group) AG-2-1·Subset 1 and AG-2-2 IV on the basis of morphology of the cultured samples, temperature-dependent growth characteristics, hyphal anastomosis reactions, and result of PCR analysis with specific primers. In Japan, damping-off on young broccoli plants caused by Rhizoctonia solani AG-1 IC, AG-2-1·Subset 2, AG-2-2 IIIB, AG-4 HG-I, and foot rot of matured broccoli caused by R. solani AG-2-2 IV has been previously reported. We investigated the pathogenicity of the two isolates using three different growth stages of broccoli plants (3-week-old, 8-week-old, and 3-month-old). Inoculated 3-week-old and 8-week-old broccoli developed severe wilt. However, inoculated 3-month-old matured broccoli showed only basal stem rot without wilt symptoms. The observed symptoms and pathogenicity were coincident with that of the damping-off on broccoli. This is the first report of damping-off on broccoli caused by R. solani AG-2-1·Subset 1 and AG-2-2 IV in Japan.