Erysiphe spp. on Fabaceae from Iran: A new insights into some complex species

Fabaceae, one of the largest flowering plant families, comprises several subfamilies and genera. Fabaceous plant species host a large number of powdery mildew species belonging to the genus Erysiphe. The affiliation of these species to Erysiphe is readily possible, but they represent a morphologically and taxonomically complicated complex of closely related, morphologically similar species with overlapping traits. Precise morphological examinations along with phylogenetic analyses, including type collections and other representative samples, are needed to solve the complexity of Erysiphe spp. on legumes. In this study, we sequenced a number of collections of powdery mildews on Pisum, Lathyrus, Vicia and Ononis spp., with a special focus on specimens from Iran, to clarify species delimitations within the Erysiphe pisi complex and other Erysiphe species complexes on legumes. Sequences retrieved from powdery mildew on Pisum and Ononis fall into separate, well supported clades. Hence, the original status of E. cruchetiana as a species of its own on Ononis spp. is reinstated instead of E. pisi var. cruchetiana. Ten species, viz., E. astragali, E. bremeri, E. caulicola, E. cruchetiana, E. iranica, E. medicaginis, E. pisi, E. rayssiae, E. sesbaniae and E. trifoliorum were confirmed for Iran, redescribed and illustrated on the basis of Iranian collections. Erysiphe astragali, E. bremeri, E. coluteae and E. crispula form a genetically little differentiated clade in ITS/LSU analyses, which is referred to as E. astragali clade (complex), comparable to the E. trifoliorum clade (complex). Based on our results, E. coluteae and E. crispula are reduced to synonymy with E. astragali and E. sophorae is considered a synonym of E. bremeri. Sequences of the North American E. intermedia on Lupinus species form a small clade nested within the big E. astragali clade. DNA of the holotype of E. sesbaniae was sequenced for the first time in this study. To use the sequences obtained from some new collections as reference sequences for phylogenetic-taxonomic purposes, we propose, for the interim, reference sequences for E. bremeri, E. caulicola, E. cruchetiana, E. pisi and E. viciae-unijugae.