Abstract
New morphological type in Rhizoctonia solani AG 1 was obtained from the sugarbeet-manufactory-waste-soils. This type was easily differentiated from two known types in Japan, 1A and 1B, in cultural appearance, especially in the size and distribution of sclerotia. Many small sclerotia (0.2-0.8mm) with dark brown to black were scattered evenly on the medium, and zonation could not be seen. In USA three types (type 1, type 2, type 3) are known in R. solani AG 1. Cultural appearance and properties of this new morphological type were almost the same as those of the type 3. Type 1 and type 2 correspond to 1B and 1A, respectively. So, we propose to designate this new type corresponding to type 3 as morphological type 1C.
Optimum temperature for hyphal growth of this type was 30C and the linear growth was 34.7mm/24hr on PDA. The width of mature main hyphae was 6.69±1.92μm. The difference of the frequency of hyphal anastomosis was seen in any combination of 1A, 1B and this type. This type had a high pathogenicity to the seedlings of Japanese radish, sugarbeet, bean, lettuce, cabbage, tomato and eggplant. This type had also been obtained from the field soils of Hokkaido, Tochgi and Fukuoka as well as from the sugarbeet-manufactory-waste-soils
