by Langer (1994). In 1971 Talbot & Keane introduced the genus Oncobasidium for a plant pathogenic species resembling Thanatephorus but lacking sclerotia and in 1972 M.A. Donk introduced the genus Ypsilondium for a species resembling Uthatobasidium but having bisterigmate (two-spored) basidia. Both genera were considered synonyms of Thanatephorus by Roberts (1999). In 1978 Tu & Kimbrough introduced the genus Aquathanatephorus for an isolate from water hyacinth which produced a teleomorph with swollen, inwardly curving sterigmata. This was redetermined as Thanatephorus cucumeris by Andersen (1996). Ceratobasidium was introduced in 1935 by American mycologist D.P. Rogers to accommodate species of the old form genus Corticium that showed affinities with the heterobasidiomycetes. These affinities were the possession of large sterigmata ("cerato-basidium" means "horned basidium") and the production of basidiospores that produce secondary spores. The genus Koleroga was proposed by Donk (1958) to accommodate K. noxia, a plant pathogen morphologically similar to Ceratobasidium but not known to produce secondary spores. Talbot (1965) demonstrated that such spores were present in some collections and suggested that Koleroga be synonymized with Ceratobasidium. Current status Molecular research, based on cladistic analysis of DNA sequences, places Rhizoctonia within the family Ceratobasidiaceae. The genus is only monophyletic, however, if species of Ceratobasidium (excluding the type) and Ceratorhiza are included as synonyms, since there is no apparent distinction between these species and species of Rhizoctonia. DNA sequencing has also confirmed the synonymy of Uthatobasidium, Oncobasidium, and Koleroga. Following changes to the International Code of Nomenclature for algae, fungi, and plants, the practice of giving different names to teleomorph and anamorph forms of the same fungus was discontinued, meaning that Thanatephorus became a synonym of the earlier name Rhizoctonia. In its current sense, therefore, the genus Rhizoctonia includes both anamorphic and teleomorphic fungi. Not all species referred to Ceratobasidium or Thanatephorus have yet been combined in Rhizoctonia, however. Redisposition of former species A comprehensive survey and redisposition of old species names in Rhizoctonia was published in 1994 by Andersen & Stalpers. Only a few frequently used names are listed below. Many older names are of uncertain application or were never validly published, or both. Rhizoctonia bataticola = Macrophomina phaseolina (Botryosphaeriaceae) Rhizoctonia carotae = Athelia arachnoidea (Atheliaceae) Rhizoctonia crocorum = Helicobasidium purpureum (Helicobasidiaceae) Rhizoctonia leguminicola = Botrytis fabae (Sclerotiniaceae) Rhizoctonia oryzae = not a validly published name but now validated as Waitea oryzae (Corticiaceae) Rhizoctonia rubi = not a validly published name and