Taxonomic reappraisal of Typhula variabilis, Typhula laschii, Typhula intermedia, and Typhula japonica

•Typhula variabilis, T. laschii and T. intermedia are distinct species.•Typhula japonica is described in detail for the first time since 1941.•A phylogenic tree derived from ITS sequences divides the genus into 3 clusters.

We have redefined Typhula variabilis, T. laschii, T. intermedia, and T. japonica on the basis of morphological and molecular evidence. Typhula variabilis, T. laschii, and T. intermedia, hitherto regarded as synonymous, were compared by critical observations of sclerotial rind cells. Rind cells of T. variabilis were thick and plateaued in the center, whereas of T. laschii had a ridge in the center. An isolate from winter wheat that we had previously identified as T. variabilis was reidentified as T. intermedia because it failed to mate with T. variabilis, even though rind cells of T. intermedia were digitate and occasionally had double-line contours, as in the case of T. variabilis. Sequencing of the internal transcribed spacer regions, including 5.8S, supported these differences, indicating that T. variabilis, T. laschii, and T. intermedia are separate species. Typhula japonica was characterized by two-spored basidia and basidiospores that often remained agglutinated with each other and germinated on basidiocarps. Its single basidiospores normally developed into dikaryotic mycelia and rarely into monokaryotic mycelia.