IDENTIFICATION OF 3 POPULATIONS OF OPHIOSTOMA-ULMI (AGGRESSIVE SUBGROUP) BY MITOCHONDRIAL-DNA RESTRICTION-SITE MAPPING AND NUCLEAR-DNA FINGERPRINTING

Three genetically distinct populations of the Dutch elm pathogenOphistoma ulmi within the aggressive subgroup were defined by the hybridization of a human minisatellite DNA sequence (HVR 33.6) to polymorphic dispersed DNA sequences within theO. ulmi nuclear genomes. For the 10 isolates examined there was a close correlation between nuclear DNA fingerprints and mitochondrial (mt) DNA restriction patterns. A restriction-site map was constructed for the mitochondrial genomes for each of these populations. The three mt DNA maps corresponded to genome sizes of 49.1 (Type I), 49.9 (Type II), and 53.9 (Type III) kilobase pairs (kbp) of DNA. The Type I and Type II mt genomes differed from the Type III mt genome by discrete length mutations of 4.8 and 4.0 kbp, respectively. It is unknown whether these length mutations resulted from insertions into or deletions from a progenitor mitochondrial genome. There was no correlation between the mitochondrial or nuclear genotypes and the geographical source of the isolates. © 1991 Academic Press, Inc.