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Appl. Environ. Microbiol., Oct 1996, 3750-3756, Vol 62, No. 10
MJ Huss, CL Campbell, DB Jennings and JF Leslie
Isozyme phenotypes were determined for 101 strains of Gibberella fujikuroi
and 2 strains of Gibberella nygamai that represent seven biological species
(mating populations) isolated from a variety of plant hosts in dispersed
geographic locations. Fourteen enzymes were resolved in one or more of
three buffer systems. Two of the enzymes, arylesterase and acid
phosphatase, were polymorphic within two or more biological species and are
suitable for intraspecific studies of population variation. Six enzymes,
alcohol dehydrogenase, aspartate aminotransferase, glucose-6-phosphate
dehydrogenase, mannitol dehydrogenase, phosphoglucomutase, and
phosphogluconate dehydrogenase, were monomorphic in all of the isolates
examined. The remaining six enzymes, fumarase, glucose phosphate isomerase,
glutamate dehydrogenase (NADP), isocitrate dehydrogenase (NADP), malate
dehydrogenase, and triose-phosphate isomerase, could potentially be used to
distinguish the different biological species. Mating populations C and D
are the most similar, since the mating population C isolates examined had
the same isozyme phenotype as did a subset of the isolates in mating
population D. Mating population E is the least similar to the other taxa
examined. Unique isozyme phenotypes are present but are composed of banding
patterns shared among the biological species. This finding supports the
hypothesis that these biological species, with the possible exception of
mating populations C and D, are reproductively isolated from one another
and that no significant gene flow is occurring between them. Isozyme
analysis is a useful method to distinguish these closely related biological
species. Examination of isozyme phenotypes is more rapid than the present
technique, which is based on sexual crosses; can be applied to strains that
are not sexually fertile; and is more sensitive than traditional
morphological characters, which cannot distinguish more than three or four
morphological groups among the seven biological species. While emphasizing
the discreteness of the mating populations as biological entities, our
isozyme data also reaffirm the close genetic relationship among these
groups.
Copyright © 1996, American Society for Microbiology
Isozyme Variation among Biological Species in the Gibberella fujikuroi Species Complex (Fusarium Section Liseola)
Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506-5502
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