Peronosporaceae species causing downy mildew diseases of Poaceae, including nomenclature revisions and diagnostic resources
2022
Crouch, J. A. | Davis, William (William J.) | Shishkoff, N. | Castroagudin, V. L. | Martin, F. | Michelmore, R. | Thines, M.
Downy mildew pathogens of graminicolous hosts (Poaceae) are members of eight phylogenetically diverse genera in the Peronosporaceae (Oomycota, Peronosporales). Graminicolous downy mildews cause severe losses to crops such as maize, millets, sorghum, and sugarcane in many parts of the world, especially in tropical climates. In countries where the most destructive GDMs are not endemic, these organisms are often designated as high-risk foreign pathogens and subject to oversight and quarantine by regulatory officials. As such, there is a need to reliably and accurately identify the causal organisms. This paper provides an overview of the Peronosporaceae species causing graminicolous downy mildew diseases, with overviews of their impact on agriculture and the environment, along with brief summaries of the nomenclatural and taxonomic issues surrounding these taxa. Key diagnostic characters are summarized and illustrated, including morphological features and DNA sequence data for types and/or voucher specimens. New sequence data for cox2 and 28S rDNA markers are provided from the type specimens of three species, including Peronosclerospora philippinensis and the first ever molecular data for Sclerospora iselematis and S. northii. Twenty-eight species are accepted, including validation of seven previously invalid taxa. Forty-one specimens are formally designated as types, including lectotypification of ten species, neotypification of three species, and holotype designation for Sclerophthora cryophila.
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