Rhizoctonia solani Kuhn [teleomorph = Thanatephorus cucumeris (Frank) Donk] is a collective species, and a taxonomic entity composed of divergent populations. Numerous attempts have been made to recognize subspecific groups within the R. solani complex, with primary emphasis on the anastomosis group (AG) system (Parmeter et al., 1969; Anderson, 1982; Ogoshi, 1987; Sneh et al., 1991). The characterization and grouping of isolates using the AG system represents a valuable approach for understanding variations within the species as well as identifying characteristics of the various groups inciting plant diseases. The AG concept however, offers no information on the genetic variation and taxonomic relationships within and between AGs in the R. solani complex.