Generic classification of some more hyphomycetes with solitary conidia borne on phialides

Abstract

Unlike most phialide-producing fungi that liberate a multiplicity of conidia from each conidiogenous cell, only single conidia are formed on phialide-like conidiogenous cells in Aphanocladium, Verticimonosporium, and some species of Sibirina. A group of isolates obtained from soil of native Artemisia tridentata (sagebrush) grassland in Wyoming and from desert soil in Iraq is compared with these genera and classified as a fourth genus, Stanjemonium, honouring Stanley J. Hughes. Phylogenetic analyses of partial nuclear small- (18S) and large-subunit (28S) rDNA sequences indicate that Stanjemonium spp. form a monophyletic group with Emericellopsis. Sequences from the nuclear 18S and 28S rDNA were too conserved to resolve morphological species of Stanjemonium; however, phylogenetic analysis of b-tubulin and translation elongation factor 1a gene exons and introns resolved all species distinguished morphologically. Numerous conidiogenous cells or denticles are scattered along the cells of aerial hyphae in Aphanocladium and Stanjemonium spp., very rapidly collapsing into denticles in the former, somewhat more persistent and leaving broad scars in the latter. In Cladobotryum-Sibirina and Verticimonosporium spp., conidiogenous cells are discrete in terminal and intercalary whorls; phialides of the latter taxon are particularly swollen. The taxonomy of Aphanocladium is not yet resolved. Two species are recognized in Verticimonosporium. Three new species of Stanjemonium are described, and one new combination from Aphanocladium is proposed, along with one new species of Cladobotryum.Key words: Aphanocladium, Cladobotryum, conidiogenesis, hyphomycetes, molecular phylogeny, phialide, Stanjemonium, systematics, Verticimonosporium.