Isozyme Variation in theAcremonium/EpichloëFungal Endophyte Complex

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Abstract
Isozyme variation of 219 isolates of Acremonium or Epichloe fungal endophytes from 17 host grass species [Lolium perenne, Agrostis hiemalis, Agrostis perennans, Brachyelytrum erectum, Elymus villosus, E. virginicus, Festuca obtusa, F. arundinacea, Glyceria striata, Holcus lanatus, Hystrix patula, Poa autumnalis, P. sylvestris, P. wulfii, Spenopholis nitida, Spenopholis pallens, Stipa robusta] was examined using starch gel electrophoresis. Ten enzyme systems selected for use out of 17 examined were variable, with three to nine distinct electromorphs per enzyme. Most isolates produced a single band per enzyme, consistent with a haploid fungus and a single isozyme locus. Double or triple bands were observed for several enzymes in certain isolates, particularly those from tall fescue. Isozyme variation was observed among isolates from 10 out of 12 different hosts where multiple isolates were sampled. Among the 52 isolates of A. coenophialum from tall fescue, 47 had the same isozyme phenotype, whereas five isolates from cultivar Triumph exhibited a different phenotype, which was most similar to A. lolii from perennial ryegrass (Lolium perenne). The relative uniformity of isolates of A. coenophialum from tall fescue probably reflects the limited number of endophyte genotypes present in the original plant material introduced from Europe. Isozyme banding patterns were not distinctive enough to distinguish between sexual Epichloe endophytes and asexual, seedborne Acremonium endophytes. There was no evidence that sexual endophytes were electrophoretically more variable within a host than asexual endophytes. Isozymes may provide useful genetic markers in future attempts to modify the grass/endophyte association.