Morphology and molecular phylogeny of a poorly known species—Erysiphe bulbouncinula (Erysiphaceae) on Koelreuteria paniculata.

Erysiphe bulbouncinula (≡ Bulbouncinula bulbosa) on Koelreuteria paniculata is a powdery mildew native and endemic in China. Fresh samples of this species were collected on K. paniculata in Sichuan Province, China, in 2018. This is the fourth confirmed identification of this species. The original description in 1932 was based on one specimen from Hangzhou and then was described in Nanjing in 1990 and in Taiwan in 1993. The morphology of the new collections of this species is described and illustrated in detail, and agrees well with the original description of the type specimen except for the number of asci (8–16 asci per chasmothecia versus 7–9 asci in the type specimen). To explore the phylogenetic position of this poorly known species, three separate phylogenetic analyses, using partial 28S rDNA and the combination of internal transcribed spacer (ITS) and 28S rDNA sequences, were conducted. The results clearly showed that E. bulbouncinula form a monophyletic clade with strong bootstrap (BS) support (MP = 100%) constituting a sister clade to E. gracilis s. lat., form a subclade with Erysiphe sect. Californiomyces and then form a big group with sect. Typhulochaeta and sect. Uncinula. Phylogenetic results confirm that E. bulbouncinula is more closely allied to Erysiphe than to Phyllactinia. Thus, this species can be maintained in Erysiphe in its current circumscription, confirming Bulbouncinula as a synonym of Erysiphe. [ABSTRACT FROM AUTHOR]