Peronospora-like fungi (Chromista, Peronosporales) parasitic on Brassicaceae and related hosts

The genus Peronospora is emended and its type species, R rumicis, is redescribed and illustrated. A new genus, Hyaloperonospora Constant., with 6 new combinations (H. floerkeae, H. lepidii-perfoliati, H. lunariae, H. niessleana, H. parasitica, and H. tribulina) is introduced to accommodate Peronospora parasitica and several other species of Peronospora parasitic on Brassicaceae, as well as those parasitic on Capparaceae, Resedaceae, Limnanthaceae, Cistaceae and Zygophyllaceae. It differs from Peronospora mainly by forming colourless conidia, large, vesicular to lobate haustoria, and often branchlets with recurved ultimate tips. Five species of Peronospora parasitic on Lepidium and Coronopus are revised and placed in the new, unispecific genus Perofascia Constant., characterised by colourless conidia, hyphal haustoria, and appressed branches. Two internal transcribed spacers (ITS1 & ITS2) and the 5.8S rRNA gene were PCR-amplified and sequenced from herbarium specimens of some representative of these taxa. Parsimony analysis of nucleotide sequence data of the regions with a high bootstrap support confirmed the generic circumscription of these fungi based on phenetic characters. A key for the identification of the taxa studied is provided and comments on their host affinity are added.