An overview on Philippine estuarine oomycetes

Abstract

Estuarine saprotrophic oomycetes are a group of eukaryotic, fungal-like protists of the Kingdom Straminipila. Species classified as estuarine oomycetes are commonly present on mangrove leaf litter and saltmarsh plant debris. They are distributed over several families (i.e. Peronosporaceae, Pythiaceae, Salisapiliaceae, and Salispinaceae). It is estimated that there are more than 100 species of estuarine oomycetes and, surprisingly, some supposedly terrestrial phytopathogenic hemibiotrophic oomycetes, e.g. Phytophthora elongata, Ph. insolita, and Ph. ramorum, are likewise present in the estuarine biome. In the Philippines, this group has been neglected for several decades as compared to the obligate biotrophic and hemibiotrophic members of Peronosporaceae and Albuginaceae. In this account, a general overview on the systematics and phylogeny of estuarine oomycetes is given. Further, the state of knowledge regarding thallus organization, taxonomy, habitat, and status of Philippine oomycetes are presented.

Adding a missing piece to the puzzle of oomycete phylogeny: the placement of Rhipidium interruptum (Rhipidiaceae)

“…Rhipidium includes the species R. americanum , R. compactum , R. interruptum ( europaeum ), R. parthenosporum , and R. thaxteri , which were recovered from a number of submerged plant substrates ( Cornu 1871 , Thaxter 1896 , Kolkwitz et al 1915 , von Minden 1916 , Kanouse 1927b , Matthews 1936 , Sparrow 1960 ). Compared to the study on pathogenic oomycetes, saprotrophs are generally less studied, even though they are increasingly gaining attention in recent years ( Nakagiri 2000 , Hulvey et al 2010 , Marano et al 2016 , Bennett & Thines 2020 ).…”

“…The phylum Oomycota is usually sorted into three groups – the early diverging lineages with several holocarpic species, and the two “crown clades” that comprise the majority of known oomycete diversity, namely the classes Peronosporomycetes and Saprolegniomycetes ( Beakes et al 2014 , Thines 2014 ). The order Rhipidiales is probably sister to the clade of all other taxa in Peronosporomycetes ( Thines 2014 ) and comprises two families, Rhipidiaceae and Salispinaceae ( Bennett et al 2018 , Bennett & Thines 2020 ), with six genera included in the former, Rhipidium , Sapromyces , Aqulinderella , Mindeniella , Nellymyces , Araiospora ( Sparrow 1960 , Emerson & Weston 1967 , Batko 1971 ), and only Salispina in the latter ( Bennett et al 2018 ). Amongst the seven genera of Rhipidiales , sequence data are exclusively available from two of them, viz.…”