ISOZYME RELATIONSHIPS OF ACREMONIUM ENDOPHYTES FROM 12 FESTUCA SPECIES

The relationships of 159 isolates of Acremonium endophytes from twelve Festuca host species, representing five subgenera, were investigated using starch gel electrophoresis of 11 enzymes. Cluster analysis of isozyme genotypes identified six distinct groupings with genetic identities (I) of 0.5 or less among groupings. Three groupings were previously described taxa associated with a single Festuca host species, A. coenophialum from F. arundinacea, A. uncinatum from F. pratensis, and A. starrii from F. obtusa. On F. arundinacea a second distinct grouping (FaTG-2) was recognized. All genotypes associated with species of fine fescue (subgenus Festuca) or with F. gigantea and F. pulchella formed another distinct grouping with identical or very similar genotypes. The endophyte from F. altissima appeared to be most divergent from all other isolates studied and may represent a separate species. Most of the gene diversity within the total isolate sample was due to differentiation among subgroups from different hosts (H(T) = 0.484; G(ST) = 0.801). In addition, morphological and cultural characteristics of representative isolates from each host were studied and found to be distinctive for all major isozyme groupings. The possibility of coevolution of endophytes along host subgenera of Festuca is discussed based on genetic relationships of endophytes and subgeneric classification of their hosts.