Two Novel Species, Phytophthora umbellatus 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 describe two isolates: a non-papillate, homothallic Phytophthora strain and a papillate, asexual Phytopythium strain. 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 multi-gene phylogenetic analyses. Furthermore, the mitochondrial genome of the new Phytophthora strain was sequenced and annotated, revealing a unique gene arrangement compared to related Phytophthora species. Based on these distinct morphological features and taxonomic status, we formally describe the two strains as new species. Detailed micro-morphological descriptions, illustrations, and molecular DNA data are provided to support their taxonomic classification.