Host-specificity ofEndophyton ramosum(Chlorophyta), the causative agent of green patch disease inMazzaella laminarioides(Rhodophyta)

The level of host-specificity of Endophyton ramosum, the causative agent of green patch disease in Mazzaella laminarioides, was experimentally tested in the laboratory. Cross-infection trials demonstrated that the endophyte has the capability of infecting a greater variety of hosts than it does in nature. Furthermore, the pattern of host-specificity does not seem to be related to the life-history phase of the host. This suggestion, however, requires further analysis as indicated by the intraspecific variability in infectivity displayed by E. ramosum from different individual hosts. Suggestions that the type of carrageenan present in the host cell walls could determine a given pattern of host-specificity are not supported by this study. In spite of this, E. ramosum seems able to discriminate between agarophytes and carrageenophytes. Agar-producing algae were rarely infected and, when the endophyte did penetrate some of them, the development of E. ramosum was atypical.