Discovery of a cryptic species, Erysiphe salicina sp. nov., and reconstruction of the phylogeny of powdery mildews on Populus and Salix spp.

Recently performed phylogenetic-taxonomic analyses of species belonging to Erysiphe sect. Uncinula on willows (Salix spp.) demonstrated a much higher diversity than previously assumed. Phylogenetic analyses and morphological examinations of Chinese Erysiphe collections on Salix abscondita (= S. raddeana), S. sinica and S. taraikensis, all belonging to Salix subgen. Vetrix sect. Vetrix, revealed an additional cryptic species which is described as Erysiphe salicina. The new species is morphologically and phylogenetically distinguished from all other powdery mildew species. The phylogeny of the new species and closely related species on Populus and Salix spp. (Salicaceae) was reconstructed and discussed using a combined alignment of the internal transcribed spacer (ITS) regions and partial 28S rDNA sequences. The present phylogenetic analyses suggest that the recently described E. salicicola (on Salix gracilistyla in Republic of Korea) has to be reduced to synonymy with E. salicis-gracilistylae comb. nov. (equivalent to Uncinula salicis-gracilistylae).