Olpidiopsis bostrychiae sp. nov.: an endoparasitic oomycete that infects Bostrychia and other red algae (Rhodophyta)

Abstract

Sekimoto S., Klochkova T.A., West J.A., Beakes G.W. and Honda D. 2009. Olpidiopsis bostrychiae sp. nov.: an endoparasitic oomycete that infects Bostrychia and other red algae (Rhodophyta). Phycologia 48: 460–472. DOI: 10.2216/08-11.1.

A holocarpic, oomycete endoparasite of the marine red alga Bostrychia moritziana collected in Madagascar and identified as Olpidiopsis sp. did not conform to morphological descriptions of any species of Olpidiopsis and had a host range that differed from that of known Olpidiopsis pathogens of red algae. We further tested the host range of this parasite and studied it by transmission electron microscopy and molecular means. It differs from other Olpidiopsis species, and we have named it O. bostrychiae. Molecular phylogenies inferred from SSU rRNA gene and COII amino acid sequences showed that O. bostrychiae branched before the main saprolegnialean and peronosporalean lineages within the monophyletic oomycetes. In the SSU rRNA gene tree, O. bostrychiae formed a clade with O. porphyrae, which infects Bangia and Porphyra spp. The two Olpidiopsis species were genetically and ultrastructurally distinct, supporting our decision to name an additional Olpidiopsis species that is parasitic on red algae.

Key Words::

• Bostrychia
• cox2
• Host specificity
• Red algae
• Sporogenesis
• SSU rRNA
• Stramenopiles
• Transmission electron microscopy

ACKNOWLEDGMENTS

We are grateful to Dr Kath White, Vivian Thompson and Tracy Davey (Electron Microscopy Research Services at Newcastle University, UK) for their support in maintaining the electron microscope facilities. We are also grateful to Prof. Joseph L. Scott (College of William and Mary, USA) for giving us many suggestions for EM fixation of this marine red algal parasite, to Prof. Gwang Hoon Kim (Kongju National University, Korea) for many helpful suggestions and to Prof. Jan Rueness and Drs Mi-Suk Hwan, Chris Schlech and Sylvia Earle for providing some isolates used in the experiment. This study was partly supported by the Sasakawa Scientific Research Grant from the Japan Science Society (grant no. 15-383M).