Debunking Duosporium

Duosporium is a monotypic genus including only the type species Duosporium yamadanum which has been treated in the literature as “anamorphic Pezizomycotina.” Nevertheless, this is just a conjecture since its true phylogenetic affinities remain unknown. This fungus is known to cause leaf spots on several members of Cyperus spp. It has been intensively investigated in the 1990s as a potential candidate for use as an inundative biocontrol agent against purple nutsedge—a major tropical weed. Its morphology was recognized, as somewhat close to those of Curvularia and Bipolaris. Nevertheless, it was kept in a separate genus based on two distinctive morphological features: production of two kinds of spores (as indicated by its generic name) and straight versicolored macroconidia. No molecular studies have ever been made to elucidate the placement of Duosporium. In a relatively recent publication, Curvularia americana and C. chlamydospora were found to produce macro- and microconidia, as in Duosporium. Besides, there are several species of Curvularia known to have predominantly straight conidia. Here, a multilocus phylogenetic analysis including the internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS) and translation elongation factor 1-α (TEF1) sequences placed D. yamadanum within Curvularia, close to C. tuberculata, C. oryzae, and C. reesi. This led to the proposal of the new combination C. yamadana and the synonymization of Duosporium with Curvularia.