Morphology and molecular phylogeny of a poorly known species-Erysiphe bulbouncinula(Erysiphaceae) onKoelreuteria paniculata

Erysiphe bulbouncinula(equivalent to Bulbouncinula bulbosa) onKoelreuteria paniculatais a powdery mildew native and endemic in China. Fresh samples of this species were collected onK. paniculatain 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 thatE. bulbouncinulaform a monophyletic clade with strong bootstrap (BS) support (MP = 100%) constituting a sister clade toE. graciliss. lat., form a subclade withErysiphesect.Californiomycesand then form a big group with sect.Typhulochaetaand sect.Uncinula. Phylogenetic results confirm thatE. bulbouncinulais more closely allied toErysiphethan toPhyllactinia. Thus, this species can be maintained inErysiphein its current circumscription, confirmingBulbouncinulaas a synonym ofErysiphe.