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

• A new powdery mildew species was found on Aucuba japonica.
• This fungus was reported as Erysiphe aucubae sp. nov.
• Morphological description and phylogenetic tree were provided.

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.