Unexpected ribosomal DNA internal transcribed spacer sequence variation within Erysiphe aquilegiae sensu lato

Erysiphe aquilegiae sensu lato is the most commonly occurring powdery mildew fungus (Erysiphales: Ascomycota) on the Ranunculaceae. Based on morphological characters, different authors have proposed the segregation of Erysiphe aquilegiae into two varieties or species. To determine if a genetic basis exists for these two taxa, the rDNA internal transcribed spacer regions of 26 specimens from five host genera, were compared by RFLP's and sequencing. The results failed to separate the two taxa, but revealed a third host-specialised taxon on Delphinium. Phylogenetic analysis revealed E. aquilegiae to be more closely related to Oidium lycopersici and E. macleayae than to the undescribed species on Delphinium