New species of aquatic chytrids from Oman

Oman is a desert country in the south of the Middle East. Springs and other water sources that harbor aquatic organisms can be separated by hundreds of kilometers. In Oct 2019, we isolated four freshwater aquatic fungi (Chytridiomycota) from benthic detritus baited with pine pollen on a general nutrient medium near Salalah, Oman. Database queries of nuc 28S rRNA (28S) and internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) revealed that one of these strains was <i>Dinochytrium kinnereticum</i>, a recently described algal pathogen from the Sea of Galilee. The other three strains had low molecular identity to available ITS sequences. These unknown strains varied in size and released endogenously swarming zoospores through papillae from mature zoosporangia. Zoospore ultrastructure was consistent with described species in the Rhizophydiales, and molecular phylogenetic results grouped these three strains into a clade in the genus <i>Rhizophydium</i>. We circumscribe these three strains as a sp. nov., thereby expanding the diversity within <i>Rhizophydium</i> described as the new species <i>R. jobii</i>. In doing so, we provide the first report of Chytridiomycota from Oman.