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Isozyme Variation in the Acremonium/Epichlo? Fungal Endophyte Complex. Adrian Leuchtmann, Department of Biology, Indiana University, Bloomington 47405, Present address: Geobotanisches Institut ETH, Zollikerstrasse 107, CH-8008 Zurich, Switzerland; Keith Clay, Department of Biology, Indiana University, Bloomington 47405. Phytopathology 80:1133-1139. Accepted for publication 7 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1133.

Isozyme variation of 219 isolates of Acremonium or Epichlo? fungal endophytes from 17 host grass species 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 Epichlo? 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.