IDENTIFICATION, DISTRIBUTION AND SAPROPHYTIC ABILITY OF TYPHULA SPECIES IN WASHINGTON AND IDAHO (EPIDEMIOLOGY)

Tester monokaryons of Typhula idahoensis C-1-48 and 70-22-26 were 98% and 100% accurate in identifying isolates of T. idahoensis and T. ishikariensis. Staining with hematoxylin revealed that the cells of isolates obtained from nature were dikaryotic, the cells of tester monokaryons (basidiospore products) were monokaryotic, and the nuclei of dikaryotic isolates of T. ishikariensis and T. idahoensis migrated into the hyphae of monokaryons of T. ishikariensis.;Disease severity increased linearly in response to a logarithmic increase in inoculum density. Maximum infection occurred with sclerotial populations at 70 to 100 sclerotia/kg of soil from Washington and 50 sclerotia/kg of soil from Idaho. The ratio of sclerotia of T. incarnata, T. idahoensis and T. ishikariensis formed on leaves to sclerotia formed on crowns and roots of winter wheat was 2:1, 22:1, and 24:1, respectively.;The percentage germination of sclerotia newly formed on winter wheat was 57%, compared with 46% for sclerotia of unknown age screened from soil. The similar percentage germination of sclerotia of different ages is evidence of some type of endogenous dormancy mechanism.;Saprophytic colonization and multiplication of Typhula species was limited as no isolates colonized dead leaves or mature straws of winter wheat. The poor saprophytic capability of Typhula was indicated further by the limited growth on soil of mycelium excised from sclerotia.;T. incarnata was the most widespread and prevalent Typhula species collected from soil and winter wheat in Washington during 1980 to 1982, a period when environmental conditions were unfavorable for snow mold. Conditions favorable for snow mold the following winter in Okanogan and Douglas Counties of Washington resulted in an increase of T. idahoensis collected from soil and plants from those counties. Suboptimal conditions for typical snow mold development results in a relative increase in T. incarnata. T. idahoensis predominated in Idaho where environmental conditions are more frequently favorable for snow mold.