ELECTROPHORETIC KARYOTYPES OF THE ELM TREE PATHOGEN OPHIOSTOMA-ULMI (SENSU-LATO)

Pulsed field gel electrophoresis using OFAGE, TAFE, and CHEF systems h as been used to more fully characterize karyotypic variation within th e two closely related fungal species of Ophiostoma ulmi sensu lato. Tw elve wild-type and laboratory strains, representing the less aggressiv e species O. ulmi and both of the biotypes of the more aggressive spec ies O. novo-ulmi were studied and their karyotypes determined. Dependi ng on the strain, a minimum of four to a minimum of eight chromosomal DNA bands were present that fall into three distinct size classes, wit h one exception. Strain CESS16K (O. novo-ulmi, North American aggressi ve subgroup) contains a unique chromosomal DNA band which comigrated n ear a Saccharomyces cerevisiae chromosome of 0.95 Mb. This unique band was the smallest O. ulmi s. l. chromosomal DNA observed. Seven of the twelve strains shared a common chromosomal DNA banding pattern, where as each of the other five had a unique karyotype. There was no correla tion between chromosome profile and species, as some O. novo-ulmi and O. ulmi strains shared common electrophoretic karyotypes.