The influence of vitamins on the growth of hyphal anastomosis groups of
Rhizoctonia solani Kühn, AG-1 (IA, sasakii type), AG-1 (IB, web-blight type), AG-2-1 (winter crop type), AG-2-2 (IIIB, rush type), AG-2-2 (IV, root rot type), AG-3 (potato type), AG-4 (praticola type), and AG-5, were studied. All isolates of AG-2-2 (IIIB), AG-2-2 (IV), and AG-5 barely grew in the medium without thiamine hydrochloride, and showed 10∼20-fold growth at 10
-5M thiamine, i.e. these groups are thiamine auxotrophic. The stimulating effect of thiamine was slight at 10
-10M and obvious at 10
-9M, and the mycelial dry weights at 10
-8 or 10
-7M were almost the same at 10
-5M. The need for thiamine is a specific character of the group, not of the isolate. Most of AG-2-1, AG-2-2 (IIIB), AG-2-2 (IV) and AG-5 isolates had their growth somewhat stimulated with 10
-5M of calcium pantothenate, but were not auxotrophic. There were two isolates of AG-2-1 that might be Ca-pantothenate auxotrophic. Some isolates had stimulated their growth with biotin, folic acid, p-aminobenzoic acid, inositol, nicotinic acid, pyridoxine hydrochloride, and riboflavin, but were not auxotrophic. The need for these vitamins is a character of the isolate, not of the group.
View full abstract