Erysiphe ruyongzhengiana sp. nov., a new powdery mildew species on Aristolochia debilis , belonging to the Erysiphe aquilegiae clade.

Powdery mildew was found on () in Jiangsu Province and Shandong Province, China. This fungus is characterized by having long conidiophore foot-cells which are straight or curved at the base, and chasmothecia with numerous appendages. Phylogenetic analysis using internal transcribed spacer sequences showed that five sequences on determined in this study and two sequences retrieved from sp. on formed an independent cluster within the clade with 58% bootstrap support. This powdery mildew differs from allied species of the clade in producing longer conidia and conidiophores with longer foot-cells, which are often curved at the base. Morphological observations and molecular phylogenetic analysis revealed a new powdery mildew species, described as .