Morphology and molecular phylogeny of Brasiliomyces malachrae,a unique powdery mildew distributed in Central and South America

Brasiliomyces, comprising only four species, is a unique powdery mildew genus characterized by having small, semitransparent chasmothecia with a thin, single peridium layer. Brasiliomyces malachrae, a type species, is distributed in Central and South America and the morphology of this species, especially its asexual morph, is poorly known. This study was performed to describe the sexual and asexual morphs of B. malachrae on Malvastrum coromandelianum in detail, and to clarify the phylogenetic placement of this fungus. The asexual morph of this species is characterized by having hyaline ectophytic mycelium with lobed hyphal appressoria and catenescent conidia. Molecular phylogenetic analyses based on 18S, 5.8S, and 28S rRNA gene sequences revealed that B. malachrae is a sister to the genus Erysiphe and situated at the boundary between tribes Golovinomyceteae and Erysipheae, which supports its unique phylogenetic position. The evolutionary relationships among the tribes Golovinomyceteae, Erysipheae, and Phyllactinieae are discussed on the basis of the present phylogenetic analyses.