Two new species of the Peronospora belbahrii species complex, Pe. choii sp. nov. and Pe. salviae-pratensis sp. nov., and a new host for Pe. salviae-officinalis
The downy mildew species parasitic to Mentheae are of particular interest, as this tribe of Lamiaceae contains a variety of important medicinal plants and culinary herbs. Over the past two decades, two pathogens, Peronospora belbahrii and Pe. salviae-officinalis
have spread globally, impacting basil and common sage production, respectively. In the original circumscription of Pe. belbahrii, the downy mildew of coleus (Plectranthus scutellarioides) was ascribed to this species in the broader sense, but subtle differences in morphological
and molecular phylogenetic analyses using two genes suggested that this pathogen would potentially need to be assigned to a species of its own. In the present study, Peronospora species causing downy mildew on members of the Mentheae, including clary sage (Salvia sclarea),
meadow sage (S. pratensis), basil (Ocimum basilicum), ground ivy (Glechoma hederacea) and coleus (Plectranthus scutellarioides) were studied using light microscopy and molecular phylogenetic analyses based on six loci (ITS rDNA, cox 1, cox 2, ef1a, hsp 90 and β-tubulin) to clarify the species boundaries in the Pe. belbahrii species complex. The downy mildew on Salvia pratensis is shown to be distinct from Pe. salviae-officinalis and closely related to Pe. glechomae, and is herein described
as a new species, Pe. salviae-pratensis. The downy mildew on S. sclarea was found to be caused by Pe. salviae-officinalis. This is of phytopathological importance, because meadow sage thus does not play a role as inoculum source for common sage in the natural habitat of
the former in Europe and Asia, while clary sage probably does. The multi-gene phylogeny revealed that the causal agent of downy mildew on coleus is distinct from Pe. belbahrii on basil, and is herein described as a new taxon, Pe. choii.
Keywords: COLEUS; DOWNY MILDEW; MULTI-GENE PHYLOGENY; NEW HOST REPORT; NEW TAXA; PERONOSPORACEAE
Document Type: Research Article
Publication date: December 1, 2020
This article was made available online on March 3, 2020 as a Fast Track article with title: "Two new species of the Peronospora belbahrii species complex, Pe. choii sp. nov. and Pe. salviae-pratensis sp. nov., and a new host for Pe. salviae-officinalis".
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