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

Abstract

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, cox1, cox2, ef1a, hsp90 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.

Alien and cryptogenic fungi and oomycetes in Austria: an annotated checklist (2nd edition)

“…As a baseline, the first checklist on alien fungi (Voglmayr and Krisai‐Greilhuber 2002 ) was first revised according to the current state of knowledge and subsequently expanded by adding newly recorded taxa. Two species that were previously included were removed within the course of the update, due to new insights in fungal systematics and re-identifications: Records from Austria that were previously identified as the North American Peronospora swinglei were recently reported to belong in fact to a different, morphologically very similar species native to Europe ( Peronospora salviae-pratensis ; Hoffmeister et al 2020 ), while the Austrian record of the East Asian Puccinia hemerocallidis was shown to be based on a misidentification of both fungus and host (Hernández et al 2002 ).…”

Downy mildew of lavender caused by Peronospora belbahrii in Israel

“…belbahrii, such as coleus, sage, nepeta, and rosemary (Ben Naim et al 2019;Thines et al 2009). While the pathogen of coleus was recently described as a species of its own (Hoffmeister et al 2020), rosemary, nepeta, and some sage species where identified as potential hosts of Pe. belbahrii by cross-inoculation experiments (Ben Naim et al 2019).…”