Restriction fragment length polymorphisms of mitochondrial DNAs from seven Fusarium species causing Fusarium head blight.

Mitochondrial DNAs (mtDNAs) were purified by CsCl/bisbenzimide density-gradient ultracentrifugation from 21 strains of seven Fusarium species that cause fusarium head blight and mycotoxin contamination in wheat and other cereals. A partial PstI clone bank, from which one of twelve PstI fragments (14.7 kb) is missing, was constructed using mtDNA from strain KU-1615 of F. graminearum. Molecular sizes of mtDNAs of single representative strains from the seven species were determined after single-, double- and triple-digestion by four or five restriction enzymes (BamHI, MluI, PstI, PvuII and XhoI), while those of others were after single-digestion by BamHI and/or PstI. MtDNA size varied from the smallest 49 kb in one strain of F. avenaceum to the largest 116 kb in one strain of F. culmorum. Restriction fragment length polymorphism (RFLP) analysis revealed a large interspecific variation, thus all the species were identified by their restriction fragment patterns and assigned to individual clusters except for F. tricinctum in that a strain studied showed identical patterns to one of two strains of F. sporotrichioides. Considerable intraspecific variation including size variation was also detected. These results indicated a high incidence of insertions/deletions both between and within species. On the basis of results obtained by the cluster analysis, some aspects of taxonomy in these Fusarium species were discussed.