Molecular phylogenetic analyses reveal a close evolutionaryrelationship between Podosphaera (Erysiphales: Erysiphaceae)and its rosaceous hosts

摘要

Podosphaera is a genus of the powdery mildew fungi belonging to the tribe Cystotheceae of the Erysipha-ceae. Among the host plants of Podosphaera, 86 % of hosts of the section Podosphaera and 57 % hosts of thesubsection Sphaerotheca belong to the Rosaceae. In order to reconstruct the phylogeny of Podosphaera and todetermine evolutionary relationships between Podosphaera and its host plants, we used 152 ITS sequences and69 28S rDNA sequences of Podosphaera for phylogenetic analyses. As a result, Podosphaera was divided into twolarge clades: clade 1, consisting of the section Podosphaera on Prunus (P. tridactyla s.I.) and subsection Magnicel-lulatae; and clade 2, composed of the remaining member of section Podosphaera and subsection Sphaerotheca.Because section Podosphaera takes a basal position in both clades, section Podosphaera may be ancestral inthe genus Podosphaera, and the subsections Sphaerotheca and Magnicellulatae may have evolved from sectionPodosphaera independently. Podosphaera isolates from the respective subfamilies of Rosaceae each formeddifferent groups in the trees, suggesting a close evolutionary relationship between Podosphaera spp. and theirrosaceous hosts. However, tree topology comparison and molecular clock calibration did not support the possibilityof co-speciation between Podosphaera and Rosaceae. Molecular phylogeny did not support species delimitationof P aphanis, P clandestina, P ferruginea, P spiraeae and P tridactyla in their current circumscriptions, whichsuggests the need for revision of these species.