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The Genetics of a Distinguishing Pigmentation Reaction of Typhula idahoensis and T. ishikariensis. G. W. Bruehl, Professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430; D. Jacobs(2), and R. Machtmes(3). (2)(3)Research assistant, and technical aide, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Phytopathology 73:928-931. Accepted for publication 9 February 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-928.

A few monokaryons of Typhula idahoensis accept nuclei of T. ishikariensis, allow migration of the foreign nuclei within their hyphae, and react to the foreign nuclei by turning brown to reddish brown when cultured on Difco potato-dextrose agar. This color reaction is visible both above in the aerial mycelium and below in the matrix in the agar. Three monokaryons of T. idahoensis that do not become discolored with prolonged incubation, that do not develop pigment when mated with T. idahoensis, and that react with pigmentation with 97% of the isolates of T. ishikariensis, have been placed in the American Type Culture Collection. These tester monokaryons should facilitate identification of these otherwise very similar species. No reciprocal reactions (ie, monokaryons of T. ishikariensis paired with dikaryons of T. idahoensis) were observed. When mycelial transfers are made from the tester monokaryons of T. idahoensis after pairing with T. ishikariensis, growth is usually reduced, but clamp connections are present. We view the discoloration and reduced growth as symptoms of general incompatibility resulting from the presence of foreign nuclei. Staining with hematoxylin revealed that all isolates from nature were dikaryons, that the testers (basidiospore products) were monokaryons, and that nuclei migrated from dikaryotic T. ishikariensis into monokaryons of T. idahoensis.