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Cultural Variation Within Typhula idahoensis and T. ishikariensis and the Species Concept. G. W. Bruehl, Department of Plant Pathology, Washington State University, Pullman 99164; R. Machtmes, Department of Plant Pathology, Washington State University, Pullman 99164. Phytopathology 70:867-871. Accepted for publication 1 May 1980. Copyright The American Phytopathological Society. DOI: 10.1094/Phyto-70-867.

By means of isolate known monokaryon (dimon) pairings, 279 isolates from Washington, Idaho, Montana, Wyoming, and Utah were identified as Tyhula idahoensis, 123 were identified as T. ishikariensis, and 21 were unidentifiable. Nuclei of the latter group migrated into tester monokaryons of either species to form clamped hyphae. Both species were highly variable in culture. In general, T. ishikariensis grew faster, produced more pigment in the medium, and the rind cells of the sclerotia were more regular than those of T. idahoensis. No easy way was found to distinguish single isolates of these species in culture and they intergraded in all characters observed. A large collection of isolates provided a continuum of cultural types. We recognized no meaningful subgroups within either species. A large collection of isolates provided a continuum of cultural types.

Additional keywords: snow molds, interspecies hybrids; taxonomy, splitting vs lumping.