Erysiphe aucubae sp. nov., a new powdery mildew species on Aucuba japonica from Japan

Abstract Aucuba japonica (Japanese aucuba), native to Japan, is an evergreen shrub distributed in the Japanese Archipelago and cultivated worldwide as an ornamental plant. A powdery mildew with Pseudoidium -type asexual morph commonly occurs on this species. Because of the absence of sexual morph (chasmothecia), the taxonomic identity of this fungus has been unclear for a long time. The new species Erysiphe aucubae is proposed for this fungus based on molecular phylogenetic analyses and a detailed morphological description of the asexual morph.