Phylogeny of Saprotrophic Oomycetes

Of the diverse lineages of the phylum Oomycota, members of the estuarine oomycetes are neglected for almost sixty (60) years as compared to the obligate biotrophic and hemibiotrophic members of Peronosporomycetes (e.g. downy mildews, and white blister rusts). Estuarine oomycetes are osmotrophic fungal-like eukaryotes that include the saprotrophic group from Peronosporaceae (i.e. Calycofera, Halophytophthora, Phytophthora, and Phytopythium), Pythiaceae (i.e. Pythium), Salispinaceae (i.e. Salispina), Salisapiliaceae (i.e. Salisapilia), and the poorly documented Rhipidiaceae (e.g. Araiospora) – a group with pedicellate and constricted hyphae, sporangia, and gametangia. It is proposed that there are approximately 100 species of estuarine oomycetes and that the supposedly terrestrial phytopathogenic species (e.g. Phytophthora elongata, Phytophthora insolita, and Phytophthora ramorum) are thriving in the estuarine environment – resulting from either a shift in habitat preference or that the trait is plesiomorphic. 

In this presentation, the recent taxonomy and evolution of the abovementioned taxa, and similarly the status of these organisms in the Philippines, are going to be presented. Concepts on thalli evolution, zoosporogenesis, sexual reproduction, and habitat are likewise introduced.