Anastomosis grouping of Rhizoctonia solani Kühn isolated from non-cultivated soils.

Abstract

Hyphal anastomosis grouping of Rhizoctonia solani isolated from non-cultivated soils in Hokkaido was attempted. From 208 soil samples of non-cultivated areas, 363 isolates were collected. Of these, 84 isolates belonged to anastomosis groups, AG-1, AG-2-1, AG-2-2, or AG-5. AG-3 and AG-4 were not detected. For classification of the remaining 279 isolates, new anastomosis groups, AG-6 and AG-BI, were established. The rates of isolation frequency of AG-1, AG-2-1, AG-2-2, AG-5, AG-6 and AG-BI were 3.0%, 1.9% 9.7%, 8.5%, 71.1% and 5.8% respectively. AG-6 was the most predominant group of R. solani in non-cultivated soils in Hokkaido.
There were similarities among the culture types of AG-1 from non-cultivated and cultivated soils, and were also the same as AG-5. Those of AG-2-1 and AG-2-2 from non-cultivated soils were different from those from cultivated soils. Cultural appearance of AG-6 was yellowish-brown or dark-brown in colour, and the tissues of sclerotium were loose. Culture types of AG-BI were variable and some of them resembled those of AG-2-1, AG-2-2, or AG-3 from cultivated soils. AG-1, AG-2-1, AG-2-2 and AG-5 from non-cultivated soils ranged from weakly virulent to highly virulent isolates. AG-6 and AG-BI were nearly avirulent.
Judging from the anastomosis behaviour and cultural appearance of AG-BI, close relations among five anastomosis groups, AG-2-1, AG-2-2, AG-3, AG-6 and AG-BI, were suggested.