Two novel species, Phytophthora umbellata, sp. nov., and Phytopythium niubeiliangense, sp. nov., from a subtropical Island in Japan and a warm-temperate forest in China

The Oomycetes are renowned for harboring several important pathogenic species, such as Phytophthora and Pythium. In this study, we described two species: a non-papillate, homothallic Phytophthora species and a papillate, asexual Phytopythium species. The strains were collected from the subtropical island of Japan and a warm-temperate forest in China, respectively. Neither strain could be fully assigned to any known taxon, so they were characterized through morphological studies and multigene phylogenetic analyses. The phylogenetic relationships were determined using four loci, namely, the internal transcribed spacer region (ITS-rDNA), cytochrome c oxidase gene (cox1), TigA gene fusion protein (tigA), and the ras-related protein (ypt1), for Phytophthora and five loci, namely, ITS-rDNA, 28S ribosomal DNA (28S-rDNA), cox1, cox2, and the beta-tubulin (β-tub) gene, for Phytopythium. Furthermore, the mitochondrial genome of the new Phytophthora species was sequenced and annotated, revealing a unique gene arrangement compared with related Phytophthora species. Based on these distinct morphological features and taxonomic status, we formally describe the two species as new species. Detailed micromorphological descriptions, illustrations, and molecular DNA data are provided to support their taxonomic classification.