Evaluation of characters available from herbarium vouchers for the phylogeny of the downy mildew genera (Chromista, Peronosporales), with focus on scanning electron microscopy

摘要

During the past five years numerous molecular phylogenies of the downy mildews have been computed. However, basic relationships of the Peronospomceae are largely unknown because molecular phylogenies are partly contradicting or do not exhibit sufficient resolution. In this study, all genera of the downy mildews with lasting sporangiophores, which have been classified as belonging to the Peronosporaceae, have been investigated. Ultrastructural synapomorphies for the genera and groups of genera are presented. Especially the fine structure of the ultimate branchlets and haustorium morphology proved to be a suitable tool to differentiate between groups of genera, whereas the commonly used criteria of branching complexity or sporangial germination did not.