Phytophthora diversity in urban forested streams of Fairfax County, Virginia, with Phytophthora matreminventam sp. nov. as the maternal parent of P. ×stagnum

Phytophthora diversity in urban forested freshwater systems of Fairfax County, Virginia was investigated by sampling 15 streams in the spring and fall from 2021 to 2024. A total of 163 isolates were identified. Based on multilocus sequence and phylogenetic analyses, they were categorized into 14 taxa belonging to 7 Phytophthora subclades including P. pseudocitrophthora in subclade 2a, P. pini in subclade 2c, P. chlamydospora, P. gonapodyides, P. matreminventam sp. nov., P. taxon bitahaiensis, and P. t. sylvatica in subclade 6b, P. lacustris in subclade 6d, P. honggalleglyana, P. irrigata, P. virginiana sensu lato, and P. sp. × Hennops in subclade 9a, P. t. polonicoides in subclade 9b, and P. intercalaris in subclade 10c. Notably, P. matreminventam sp. nov. named in this study was determined to be the maternal parent of P. × stagnum based on their unique genetic traits. Although a few species recovered in this study reportedly possess innate pathogenicity to woody plants, no significant symptoms of Phytophthora diseases were observed in the nearby forests at the sampling sites.