Ectocarpus, a cosmopolitan genus of filamentous marine brown algae, contains two species, E. siliculosus and E. fasciculatus. Both species are subject to virus infections, which either destroy the host's sporangia or persist in a latent state without visible symptoms. We used PCR amplification of a viral gene fragment to monitor the infection status of Ectocarpus samples from Gran Canaria Island, North Atlantic, and southern Chile over 26 months.
At both sites, we found persistently high levels of pathogen prevalence: 40–100% of the Ectocarpus specimens from Chile and 55–100% from Gran Canaria contained viral DNA. No evidence for seasonal variation could be detected. We conclude that vertical transmission of viral DNA through mitotic zoospores of the host is the key mechanism for the persistence of the pathogen. The PCR amplification characteristics of samples from Gran Canaria indicate that two different virus genotypes coexist in the same host population.