Phylogenetic relationships of Microsphaera and Erysiphe section Erysiphe (powdery mildews) inferred from the rDNA ITS sequences

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Abstract
The genus Microsphaera has been considered to be derived from section Erysiphe of the genus Erysiphe by a single event. Cleistothecial appendages are the most distinct difference between the two genera and have an important role for overwintering. To understand the phylogenetic relationship between Erysiphe section Erysiphe and Microsphaera more precisely, phylogenetic trees were constructed using the nucleotide sequences of the rDNA ITS region from 11 Erysiphe (section Erysiphe) and 16 Microsphaera taxa. The phylogenetic trees indicated the close relationship between the two genera. However, the genera Erysiphe (section Erysiphe) and Microsphaera did not group into separate monophyletic lineages; instead, they formed several small clusters that were mixed together. This result suggests that the differentiations of the genera occurred two or more times independently. This also supports the idea that appendage morphology does not always accurately reflect the phylogeny of the powdery mildews because the morphology of appendages may evolve convergently under the selection pressure of their particular biotopes (host plants).