Erysiphe viburni-plicati and Podosphaera photiniae, two new species of Erysiphales (Ascomycota) from Japan

•Two new species of the Erysiphales are described and illustrated.•Erysiphe viburni-plicati was found on Viburnum plicatum var. plicatum f. glabrum.•Podosphaera photiniae was found on Photinia villosa.•Monoascus-type chasmothecia are not confined to Podosphaera and Cystotheca.

Two new species of the Erysiphales, Erysiphe viburni-plicati and Podosphaera photiniae, are described and illustrated in this paper. These two fungi were first reported in 1977 and 1996 as Podosphaera spp. from Japan, but have not yet been formally described and named. We performed detailed morphological re-examinations and phylogenetic analyses based on new specimens. The results clearly show that these fungi are new, hitherto undescribed species. Molecular analyses of E. viburni-plicati indicate that this fungus belongs to the genus Erysiphe, not to Podosphaera, although it has chasmothecia with a single ascus. This result reveals that monoascus-type chasmothecia are not confined to Podosphaera and Cystotheca as they are also formed by some Erysiphe species.