Phylogeny and taxonomy of powdery mildew caused by Erysiphe species on Lupinus hosts

Authors: BRADSHAW, MICHAEL - Orise Fellow; BRAUN, UWE - Martin Luther University; GÖTZ, MONIKA - Federal Research Centre (FAL); Jurick, Wayne

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Accurate and rapid fungal identification is the first important step to a successful integrated pest management plan. Different species of plant pathogens often require integrated management techniques. Phylogenetic evaluation of fungi leads to improved control and is a basis for futurex research. In this manuscript we identified a new species of powdery mildew infecting Lupinus species and evaluated common powdery mildews on plants in the pea family (Fabaceae). This family includes numerous agricultural and economically important crops. For example, species within the genus Lupinus and the family Fabaceae are commonly cultivated for their ornamental value, protein rich animal fodder, value as a cover crop due to their symbiotic relationships with Rhizobium, and as a protein rich food source for humans. We conducted multiple analyses to confirm all the powdery mildew species infecting Lupinus species. This information is important for the agriculture industry to determine which powdery mildew is a major disease so that efficient management strategies can be employed.

Technical Abstract: Species in the genus Lupinus (Fabaceae) comprise over 250 plant species located throughout the world. Powdery mildews, caused by Erysiphe species, are common pathogens infecting these ecologically, ornamentally and agriculturally important plants. In the present work we conducted phylogenetic and taxonomic analyses on Erysiphe species colonizing hosts of the leguminous genus Lupinus, using sequences from the internal transcribed spacer (ITS) and 28S genomic regions. Powdery mildews of the genus Erysiphe on Fabaceae are taxonomically intricate and challenging. Therefore, it was necessary to put the sequences retrieved from lupines in a broader context of common and allied powdery mildew species of leguminous plants, including Erysiphe astragali, E. baeumleri, E. pisi, and E. trifoliorum. The new species Erysiphe lupini, found in the USA on Lupinus lepidus, L. polyphyllus, and Lupinus sp., is described and illustrated. Additionally, Erysiphe intermedia (' Microsphaera trifolii var. intermedia) has been confirmed as a North American lupine powdery mildew that is a sister group to E. astragali on Astragalus spp. Sequences retrieved from E. astragali form a well-supported clade. European Erysiphe collections on lupines were often referred to as E. intermedia, but our phylogenetic analyses and morphological re-examinations have shown that they pertain to E. trifoliorum. The E. trifoliorum ITS+28S cluster is composed of sequences belonging to several species, including E. baeumleri, E. euonymi, E. hyperici, and E. trifoliorum, which cannot be sufficiently resolved on a species level. Morphological and biological differences between the species are discussed and provide evidence that the species concerned should be maintained. Future research should take a multi-locus approach to resolve the E. trifoliorum complex. On a broader scale, the phylogenetic analysis conducted confirmed that Pisum sativum (pea) can be colonized by two Erysiphe species, E. pisi and E. trifoliorum. Erysiphe diffusa (s. lat.) is an additional species occurring on lupines in North and South America. Finally, a sequence obtained from a powdery mildew collected in Portugal on the native Lupinus micranthus pertained to the Ersiphe guarinonii cluster. This collection, could belong to the latter species or to an undescribed cryptic taxon and is tentatively treated as Erysiphe sp. Final conclusions require additional collections. To fix the application of the species names E. astragali, E. baeumleri (including its synonym E. marchica), and E. intermedia, epitypes have been designated for these taxa with ex-epitype sequences.