Characterization and pathogenicity of Rhizoctonia spp. causal agent of summer blight in pasture grasses and legumes in Japan
1993
Tsukiboshi, T. (National Grassland Research Inst., Nishinasuno, Tochigi (Japan)) | Kimigafukuro, T.
The characteristics and pathogenicity of Rhizoctonia spp., causal agent of summer blight of herbages, were analyzed. Rhizoctonia spp. were isolated from diseased orchardgrass, ryegrass, fescue, clover, alfalfa and other pasture crops in Japan. The isolates of R. solani were assigned to the anastomosis groups (AG) of AG-1, AG-2-1, AG-2-2, AG-4 and AG-5. Other bi- and multinucleate Rhizoctonia spp. were also isolated. R. solani AG-1 including the intraspecific group Ia (sasakii-type sclerotia) and Ib (microsclerotia) was the major group which accounted for 82.5% and 59.1% of the isolates from grasses and legumes, respectively. The ratio of appearance of AG-1-Ib in the AG-1 isolates from grasses and legumes which ranged from 61.5 to 63.6% was very high compared with that of the AG-1 isolates from corn (5.6%). The isolates of AG-1-Ib were mainly collected from the northern part of Japan and appeared to be distributed in the cool area based on the better hyphal growth under relatively low temperatures of hyphal growth. In the greenhouse, both isolates of R. solani AG-1-Ib and Ia were generally virulent to grasses, legumes and corn compared with those of other AG groups of R. solani and Rhizoctonia spp. It was concluded that the main causal agents of summer blight of herbages were R. solani Ag-1-Ib and Ia and no host specificity in relation to pathogenicity was detected among these isolates
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