GREEN PATCH DISEASE IN IRIDAEA-LAMINARIOIDES (RHODOPHYTA) CAUSED BY ENDOPHYTON SP (CHLOROPHYTA)

A green mottled coloration, or green patch disease, develops in the red alga Iridaea laminarioides Bory when it is infected by the algal endophyte Endophyton sp. The disease is widespread in host populations along the coast of central and southern Chile (33-degrees-17' S to 40-degrees-33' S) and affects both gametophytic and sporophytic fronds. It is characterized by green areas, usually located at the base of the thalli, which become soft in texture in fully developed infections. The softening of the host tissue is caused by cellular destruction resulting from endophyte-mediated compaction of the cells, followed by secondary bacterial infections. Bacteria gain access to the host through openings left in the host thallus during spore release from mature sporangia of Endophyton. Both life-history phases of L laminarioides were successfully infected by unialgal isolates of Endophyton in laboratory trials. Infection was achieved only by germlings from newly settled spores and the process of penetration was completed within 3 d. Softening of laboratory-infected thalli became evident about 8 wk after penetration and thallus destruction was complete after 3 to 4 mo of culture.