COMPARISON OF 2 DNA VIRUSES INFECTING THE MARINE BROWN-ALGAE ECTOCARPUS-SILICULOSUS AND ECTOCARPUS-FASCICULATUS

The marine brown algal genus Ectocarpus contains two species, E. silic ulosus and E. fasciculatus, Field populations of both species include plants with infection symptoms caused by DNA viruses, We have establis hed clonal cultures from infected and normal host plants and investiga ted the properties of the endogenous viruses, Both host species contai n virus particles with a hexagonal cross-section and a diameter of ca, 150 nm, The genomes of both virus types consist of double-stranded DN A, approximately 320 kb in size, Restriction digestion with Sfil revea led differences between the two virus genomes, However, PCR experiment s suggest that at least one gene, which encodes a major capsid protein , is quite similar in both virus species, In cross-infection experimen ts the E. siliculosus virus did not initiate an infection cycle in E. fasciculatus. In contrast, the E. fasciculatus virus infected E. silic ulosus zoospores. The resulting plants showed aberrant symptoms and pr oduced virus particles which were not infectious, We conclude that the two Ectocarpus species are hosts for different, but closely related v iruses.