ISG-specific ribosomal DNA polymorphism of the Rhizoctonia solani species complex

Rhizoctonia solani Kuhn (teleomorph Than? atephorus cucumeris (Frank) Donk), a species complex, contains divergent groups of plant pathogenic and saprophytic forms (Adams, 1988; Farr et al., 1989; Sneh et al., 1991). It is primarily identified by anamorphic characteristics because of the lack of an informative teleomorph (Parmeter, 1970). Isolates within the species are grouped based on their anastomosis behavior, and at least 11 anastomosis groups (AGs) have been reported (Ogoshi et al., 1990; Sneh et al., 1991). AG classification has been helpful for over half a century. However, the mechanisms of anastomosis are not fully understood. Isolates from some AGs are able to anastomose at varied