Phytophthora umbellatus sp. nov., a novel species of Phytophthora from the Subtropical Island of Japan
Description
A non-papillate, homothallic Phytophthora species was isolated from Amami Island in the subtropical region of Kagoshima Prefecture, Japan. This isolate could not be assigned to any existing taxon and was characterized through morphological studies and phylogenetic analyses. The novel isolate was found to differ from closely related Phytophthora species based on several distinctive features, including intercalary hyphal swellings, non-caducous and non-papillate sporangia with nested proliferation, clustered chlamydospores, a homothallic sexual phase, smooth oogonia with a tapered base, predominantly amphigynous antheridia, aplerotic oospores, and a lower optimum temperature for growth. In phylogenetic analyses involving sequences from four loci, the isolate formed a distinct monophyletic group within Phytophthora subclade 9c, exhibiting strong bootstrap support. Additionally, the mitochondrial genome of the new isolate was sequenced and annotated, revealing a distinct gene arrangement when compared with related Phytophthora species. Therefore, based on its unique morphological characteristics and taxonomic status, the isolate is described here as a new species formally designated as Phytophthora umbellatus sp. nov.