Analysis of digitized herbarium records and community science observations provides a glimpse of downy mildew species diversity of North America, reveals potentially undescribed species, and documents the need for continued digitization and collecting

Peronosporaceae Species Causing Downy Mildew Diseases of Poaceae, Including Nomenclature Revisions and Diagnostic Resources

“…Graminicolous downy mildews are predominantly tropical or subtropical, with only two of the seven genera, Sclerophthora and Sclerospora , extending into cool temperate climates ( Spencer & Dick 2002 , Davis & Crouch 2022a , b ). As most tropical ecosystems are generally understudied, our current knowledge of the GDMs is restricted to species occurring on crops and some anecdotal reports from wild grasses ( Waterhouse 1964 , Shaw 1975 , this paper).…”

“…Any taxonomic or nomenclatural confusion that would lead to the misidentification of species or misapplication of a name could hinder efforts to identify introduced species, detect emerging pathogen threats, and track the spread of disease ( Thines & Choi 2016 , Petrželová et al . 2017 , Davis & Crouch 2022a ). However, this group has never been monographed, and practical diagnosis of GDM pathogens is hindered by the absence of an updated, centralized treatment of the group.…”

Genetic structure of Plasmopara halstedii populations across Europe and South Russia

“…However, without a molecular investigation of the type specimen of P. halstedii it cannot be concluded whether the name P. halstedii needs formal taxonomic action to keep it as a name for the causal agent of SDM. Recently, Davis and Crouch (2022) noted that applying a narrow host range concept to the MyCoPortal records of P. halstedii sensu lato may split the species significantly, as there are 733 specimens from hosts other than the type host E. purpureum ; these have been identified from 27 host genera and thus may represent members of undescribed species.…”

“…However, without a molecular investigation of the type specimen of P. halstedii it cannot be concluded whether the name P. halstedii needs formal taxonomic action to keep it as a name for the causal agent of SDM. Recently,Davis and Crouch (2022) noted that applying a narrow host range concept to the MyCoPortal records of P. halstedii sensu lato may split the species significantly, as there are 733 specimens from hosts other than the type host E. purpureum; these have been identified from 27 host genera and thus may represent members of undescribed species.Altogether, our study (a) suggests that P. halstedii populations on sunflower across Europe mirror the effect of exchange of potentially infested seeds on the genetic structure of pathogen population, and (b) supports prevailing asexual reproduction within P. halstedii metapopulations. Moreover, analysis of P. halstedii samples originating from H. × laetiflorus differentiated them from those infecting H. annuus, thus supporting the need for a taxonomic revision of the species P. halstedii sensu lato.…”

From Dormant Collections to Repositories for the Study of Habitat Changes: The Importance of Herbaria in Modern Life Sciences

“…At the same time, resources previously used for traveling to collections could instead be spent mining data simultaneously across many collections, via online open-access consolidated data portals, using digitized collections to identify and annotate specimens in other herbaria [10,14,16]. Interestingly, several digitization projects also made old and ancient figurative herbaria available, which reported data about the discovery, description, and distribution of each painted plant species; therefore, the availability of data on plant biodiversity from the 16th century actually indicates the anticipation of the advent of modern herbaria [17,18].…”