Data from: Where Flowers Bloom, so do Downy Mildews: New Species and New Records of Hyaloperonospora, Peronospora, and Plasmopara Species on Ornamental and Wild Plants in the United States

Downy mildews are biotrophic plant pathogens in the family Peronosporaceae (Peronosporales, Oomycota) of high value crops which can cause significant damage and economic losses. The floral and nursery crop industries are particularly susceptible to downy mildews, especially when annuals, perennials, and woody plants are growing in protected environments. In addition to affecting cultivated plants, downy mildews are a common occurrence on wild relatives, or non-cultivated plant hosts. The role these play, however, as pathogen reservoirs and on the emergence or re-emergence of downy mildew epidemics is still unknown. In this study, we report downy mildew disease observations on several annual, perennial and woody shrub plants in several states in the Eastern U.S. Based on morphological observations and phylogenetic analyses of two nuclear loci (Internal transcribed spacer 1 and 2, 28 ribosomal large subunit) and two mitochondrial loci (cytochrome oxidase subunits 1 and 2), we report Peronospora and Plasmopara occurrences on frost grape (Ohio), Lenten rose (North Carolina, Virginia), mock strawberry (Maryland), redbud (North Carolina), snapdragon (Virginia), viburnum (North Carolina), and Virginia creeper (Maryland, Ohio). The phylogenetic analysis indicated that the Peronospora isolates on snapdragon (Antirrhinum majus) from Virginia were clearly separated from other P. antirrhini isolates collected on Misopates orontium, indicating that they constitute a separate species here described as Pe. ceperoae (dataset containing SNPs for species identification here included). The phylogenetic analyses also supported the combination of Peronospora matthiolae, a pathogen of Matthiola incana (stock), into Hyaloperonospora, based on specimens collected in Ohio. Collectively, our results suggest a wider geographic distribution for the downy mildew species reported, highlighting the need for continuous surveillance of these pathogens to prevent outbreaks and their introduction to naïve environments.