MITOCHONDRIAL-DNA RESTRICTION PATTERNS OF PHIALOPHORA-GREGATA ISOLATES FROM SOYBEAN AND ADZUKI BEAN

Mitochondrial DNA was examined from 20 soybean and seven adzuki bean Phialophora gregata isolates. The restriction enzyme fragment patterns of mitochondrial DNA for five restriction enzymes were compared among the soybean fungal isolates to determine if restriction fragment length polymorphisms could be detected from isolates collected from Illinois, Indiana, Wisconsin, Ohio, Minnesota, and Iowa soybean fields. No differences in mitochondrial DNA restriction fragment patterns were detected among the 20 soybean fungus isolates. Restriction fragment length polymorphisms were detected between adzuki bean and soybean isolates. Two groups, based on restriction fragment length polymorphisms, could be distinguished within the adzuki bean fungus isolate collection. One group, composed of three isolates, had 33% of the mitochondrial DNA restriction fragments that comigrated with the soybean reference isolate. The other group, composed of four isolates, had no bands in common with either the other three adzuki bean isolates or the soybean reference isolate. All four of these isolates had identical mitochondrial DNA restriction fragment patterns. These isolates morphologically appeared to be unidentified Acremonium species isolates rather than unidentified Phialophora species. Restriction fragment patterns of mitochondrial DNA may be a valuable aid in identifying Phialophora isolates as well as an aid in separating Phialophora isolates from Acremonium isolates that are associated with vascular browning of soybean and adzuki bean plants.