FACILITATING ANASTOMOSIS GROUPING OF RHIZOCTONIA-SOLANI ISOLATES FROM COOL-SEASON TURFGRASSES

Determining anastomosis groups (AGs) of Rhizoctonia solani Kuhn isolates is tedious and time-consuming. Three previously described methods (i.e., cellophane strip, glass slide, petri dish) were compared to determine which was the most rapid and accurate. Colony characteristics also were assessed to tentatively identify AGs. All techniques were accurate. The cellophane strip method was most time-consuming, acid the time required for hyphal overlap with the glass slide method was not generally predictable. Pairing isolates in a petri dish containing a thin layer of water agar was reliable and was the simplest technique. There was little variation in colony pigmentation or sclerotia color, shape, or formation patterns within AG-1 IA (n = 34), AG-2-2 IIIB (n = 46), and AG-4 (n = 5); the former two AGs are the ones most commonly isolated from cool-season turfgrasses. Accordingly, R. solani isolates from turfgrasses may be assigned tentatively to an AG based on colony pigmentation and sclerotial characteristics.