Anastomosis groups among isolates of Ceratobasidium cornigerum and related [Rhizoctonia solani-like] fungi [Includes a list of their plant hosts]

Hyphal anastomosis was studied among 85 isolates of binucleate Rhizoctonia solani-like fungi. On the basis of pairings, seven anastomosis groups (CAG) were discovered and designated CAG 1 through CAG 7. Seventy-one isolates were assigned to the seven CAG. No hyphal fusion occurred in pairings between 54 isolates, randomly selected from the seven CAG and isolates of R. solani AG 1, 2, 3, or 4. Within each CAG there was little homogeneity with respect to host, plant part invaded, and geographic origin, with the exception of CAG 1 isolates, which were found associated only with members of the Gramineae. CAG 2 included isolates of R. ramicola and R. fragariae. Four isolates in this group were induced to sporulate and were identified as Ceratobasidium cornigerum. CAG 6 included an isolate of R. muneratii. The absence of dark mycelial and sclerotial pigmentation among the majority of isolates in CAG 1, 2, and 7 was the significant cultural feature distinguishing isolates in these groups from isolates in other anastomosis groups and from isolates of R. solani. Isolates in CAG 3, 4, and 5 formed dark mycelial and sclerotial pigments similar to those produced by isolates of R. solani. The biologic and taxonomic implications of the anastomosis groups are discussed.