A new endoparasite Olpidiopsis heterosiphoniae sp. nov. that infects red algae in Korea

A new species of Olpidiopsis, which infects dasyaceaen algae in Korea, is established. This endoparasite was first collected from Heterosiphonia pulchra, thus we named it O. heterosiphoniae. The infection process and asexual life history of O. heterosiphoniae were similar to previously reported Olpidiopsis species except for the cell type-specific infection in its host. The infection occurred mainly at the distal cells of determinate branches and was rarely observed in the other parts of the filament. The pathogen was transferred to another host, Heterosiphonia japonica, and the host-parasite dual culture has been kept in the laboratory for more than ten years since it was collected in May 2006. Up to 15 sporangia of 20-100 μm in size developed in a single infected host cell. One sporangium contained between 8 and 128 zoospores at maturity. Zoospores were kidney-shaped, 3-4 μm in size, with two laterally inserted flagella. Multigene analyses combining 18S rRNA, cox1 and cox2 genes showed that O. heterosiphoniae belonged to the lineage infecting filamentous red algae from the orders Ceramiales and Bonnemaisoniales. Epidemiological studies in Pyropia farms in Korea showed that O. heterosiphoniae may not be a main causative agent of Olpidiopsis blight in sea farms, although it is able to occasionally infect gametophyte blades of Pyropia tenera.