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Two new species of Erysiphe section Uncinula are described and illustrated based on the molecular and morphological analyses: (1) Erysiphe fernandoae sp. nov. on Fernandoa adenophylla is distinct from other Erysiphe species on the plant family Bignoniaceae by having smaller asci, ca 12 appendages per chasmothecium and being found only in Asia; (2) Erysiphe michikoae sp. nov. on Celtis jessoensis differs from Erysiphe kusanoi on other Celtis species in having smaller chasmothecial, ascal and ascospore dimensions, and fewer number of chasmothecium appendages. The phylogenetic relationships of the two new species with other closely related species are discussed based on 28S and ITS rDNA sequences.

The Erysiphaceae are a group of obligately biotrophic fungi that cause powdery mildew disease of angiosperms. Due to their inability to be cultured on artificial media, the taxonomy of the Erysiphaceae has generally been based on the morphological characteristics of fresh and herbarium specimens. Thus, several morphological species with wide host ranges have long been maintained in this family, even though they clearly consist of several biological species. Erysiphe galii has been known as a powdery mildew of Galium spp. Recently, the former E. galii var. galii has been reassessed as Neoerysiphe galii and E. galii var. riedliana as Golovinomyces riedlianus, along with a taxonomic revision of the generic concept of the Erysiphaceae. The present study was conducted to evaluate the validity of the taxonomic revision of the two varieties of E. galii. During the course of this study, we found that the Galium powdery mildews consist of at least four different species, viz. Neoerysiphe galii, Golovinomyces orontii, G. riedlianus, and an unknown species collected in Argentina. The latter species is described as a new species, Golovinomyces calceolariae. The three species belonging to Golovinomyces are morphologically very similar to each other, i.e. the discrimination between them is rather difficult. The morphological differences of the three Golovinomyces species of Galium are discussed.

A phylogenetic analysis of the Erysiphe with uncinuloid ascoma appendages (Erysiphe section Uncinula, Erysiphales, Ascomycota) on Carpinus spp. was done using sequences of the rDNA ITS regions and the D1/D2 domains of the 28S rDNA. These results, combined with morphological data, revealed a complex consisting of several distinct taxa. These included the already described Erysiphe carpinicola on C. japonica distinguishable from the Erysiphe sp. on C. betulus and C. tschonoskii as well as the one on C. laxiflora. Thus, it was shown that Oidium carpini, described from Europe on Carpinus betulus, the powdery mildew with uncinula-like ascomata, recently found in Europe on this host, as well as an Erysiphe on C. tschonoskii in Japan, described previously as E. carpinicola, all belong to a single new species, named E. arcuata in this paper. As the powdery mildew on C. laxiflora was also distinct from other known species, it is named E. carpini-laxiflorae in this paper. The already described E. pseudocarpinicola and Erysiphe sp. on Carpinus cordata are two additional taxa, which are morphologically and genetically distinguished from the other species of Erysiphe sect. Uncinula on Carpinus spp.

Powdery mildew on cherry bark oak (Quercus falcate var. pagodifolia) collected in Tennessee, USA, was determined to be Erysiphe abbreviata, a species confined to North America. The diagnostically important anamorph of this species is described for the first time. Sequence analyses of the rDNA ITS region and D1/D2 domains of the 28S rDNA were used to obtain phylogenetic data for and taxonomic conclusions about this species. The structure of the anamorph (Oidium subgen. Pseudoidium) and the molecular data support the placement of this species in Erysiphe emend. (including Microsphaera) as a species separate from the Eurasian Erysiphe alphitoides.