First comprehensive phylogenetic analysis of the genus Erysiphe (Erysiphales, Erysiphaceae) II: the Uncinula lineage

摘要

Phylogenetic relationships of the Uncinula lineage, which is the basal group in the genus Erysiphe, were investigated with 167 sequences of nuc ITS1-5. 8S-ITS2 and the 28S rDNA regions. Backbone tree analyses with six datasets and two tree-constructing methods revealed that the Uncinula lineage is, divided into seven distinct clades. Glades 1-5 each contained a representative powdery mildew species, namely E. australiana in Glade 1, E. liquidambaris in Glade 2, E. adunca in Glade 3, E. fraxinicola in Glade 4 and E. actinidiae in Glade 5. Glade 6 comprises 71 sequences including the Microsphaera lineage and 17 species of the Uncinula lineage, such as E. carpinicola, E. carpinilaxiflorae, E. miyabei, E. glycines and E. necator. Topology tests supported the Microsphaera lineage forming a monophyletic clade in Glade 6, suggesting that Microsphaera-type appendages appeared only once in this clade to diverge into the Microsphaera lineage. Glade 7 consists of 72 sequences containing 30 species, including species of sects. Californiomyces and Typhulochaeta, four species from Nothofagus, species of sect. Erysiphe parasitising herbaceous plants belonging to the Asteraceae, Rosaceae and Saxifragaceae. Molecular clock analysis suggests that the major seven clades appeared 50-30 million years ago (Ma) in the Paleogene Period. The Microsphaera lineage may have split from the Uncinula lineage at the boundary of the Paleogene and Neogene, when appendages with dichotomously branched tips appeared. The clade of the species on Nothofagus split from the northern hemisphere species about 20-10 million years ago (Ma) in the Miocene Epoch, and host-shift from trees to herbs also might have occurred in this period.