A new peronosporomycete, Halioticida noduliformans gen. et sp. nov., isolated from white nodules in the abalone Haliotis spp. from Japan Abstract Four strains belonging to the Peronosporomycetes (formerly Oomycetes) were isolated from white nodules found on the mantle of three species of abalone. In artifi cial seawater, the four isolates formed fragments such as in the genus Haliphthoros, but the protoplasm constriction was weaker, and fragments were longer, with smaller spaces between them, than those of Haliphthoros. The four strains form one or more discharge tubes from each zoosporangium. The four strains were similar, but not identical, to the genus Haliphthoros based on morphological characteristics. As a result, the four isolates were classifi ed in a new genus and species, Halioticida noduliformans gen. et sp. nov. Phylogenetic analysis of the D1/D2 region of the large subunit ribosomal RNA gene (LSU rDNA) was performed, and the four isolates showed 100%-99.8% concordance. In the phylogenetic tree, the four isolates were not classifi ed in the subclass Peronosporomycetidae, Saprolegniomycetidae, or Rhipidiomycetidae. However, the four isolates formed a new clade with genera Haliphthoros and Halocrusticida in Peronosporomycetes. Within this new clade, the four isolates, Haliphthoros spp. and Halocrusticida spp., were grouped in their respective independent subclades. These results showed that these were the new genus and species from the morphological characteristics.
A new peronosporomycete, Halioticida noduliformans gen. et sp. nov., isolated from white nodules in the abalone Haliotis spp. from Japan Recently, DNA sequence-based molecular phylogenetic studies of the Peronosporomycetes have been carried out to assist morphologically based taxonomy. Nuclear ribosomal RNA gene regions such as the small subunit ribosomal RNA gene (18S rDNA), the D1/D2 region of the large subunit of ribosomal DNA (LSU rDNA), and internal transcribed spacer (ITS)l-5.8S-ITS2 regions have been used to analyze phylogenetic relationships in the Peronosporomycetes (
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