Abstract
In relation to 6 anastomosis groups in Rhizoctonia solani (Thanatephorus cucumeris), effect of temperatures on mycelial growth, hyphal widths, numbers of nucleus and colonial appearances were studied comparatively.
Most isolates belonging to the group AG-1 grew rapidly at 28°C, but slightly at 35°C. Among 6 groups they grew most rapidly (about 30mm/day) at their optimum temperatures. The tissue of sclerotium was compact. The group AG-1 includes Corticium sasakii and C. microsclerotia. Most isolates of the group AG-2 grew rapidly at 23-25°C, but not at 33°C. On the mycelial colonies of the isolates small reddish-brown sclerotia were formed in concentric zones. Most isolates of the group AG-3 grew well at lower temperature as AG-2. Their hyphal widths were largest in 6 groups. Most of this group were isolated from potatoes. Isolates of the group AG-4 were able to grow at 35°C. Their hyphal widths were narrowest in contrast to AG-3. This group is the “praticola type” and their cultural colonies are mealy. Most isolates of the group AG-5 were from soils and their macroscopic appearances were yellowish. Most of the group-AG-6 were isolates from sugar beet and soils to which sugar beets had been cultivated. Their mycelial colonies were dark-brown in color, and the tissue of sclerotium was loose.
AG-1, AG-2, AG-3, and AG-4 correspond with I, II, III, and IV of Schultz, A, D, F, and C of Richter and Schneider, AG-1, AG-2, AG-3 and AG-4 of Parmeter et al., and sasakii type and web-blight type, winter crops type, potato type, and praticola type of Watanabe and Matsuda, respectively. AG-5 perhaps corresponds with B of Richter and Schneider. AG-6 corresponds with rush type and root rot type of Watanabe and Matsuda.
