Devriesia, a new hyphomycete genus to accommodate heat-resistant, cladosporium-like fungi

Abstract

Three new species of heat-resistant fungi related to the hyphomycete Cladosporium staurophorum (Kendrick) M.B. Ellis were isolated from heat-treated soil from commercial lowbush blueberry fields and other sites in eastern Canada. Cladosporium staurophorum and the three new species produce characteristic dark, multicelled chlamydospores. Phylogenetic analysis of nuclear ribosomal internal transcribed spacer DNA sequences suggest that these four species form a monophyletic group that is marginal in the Mycosphaerellaceae and phylogenetically distinct from Cladosporium sensu stricto. The new genus Devriesia is described for C. staurophorum, the three new species, and a fifth species originally described as Cladosporium chlamydosporis. A key to distinguish the five accepted species is provided. The species of the genus are dimorphic and share similar cladosporium-like conidial anamorphs consisting of pale brown, short, acropetally produced chains of cylindrical to fusiform, zero- or one-septate conidia and ramoconidia, diagnostic chlamydosporic synanamorphs, and a soil-borne, heat-resistant ecology. Devriesia acadiensis N.L. Nickerson & Seifert, with clover-shaped chlamydospores, Devriesia shelburniensis N.L. Nickerson & Seifert, with large, multicelled chlamydospores, and Devriesia thermodurans N.L. Nickerson & Seifert, with few-celled, clavate chlamydospores, are described as new species. Chlamydospores from cultures of D. acadiensis, Devriesia staurophora, and D. thermodurans germinated after exposure to 75°C for 30 min. Germination of these spores was activated by a heat shock. Chlamydospores from cultures of C. shelburniensis did not germinate after heat exposure.