DE-NOVO GENERATION OF MITOCHONDRIAL-DNA PLASMIDS FOLLOWING CYTOPLASMIC TRANSMISSION OF A DEGENERATIVE DISEASE IN OPHIOSTOMA-NOVO-ULMI

A mitochondrial DNA plasmid was detected in an isolate of Ophiostoma novo-ulmi with a degenerative disease. The DNA plasmid was shown to be derived from the mitochondrial DNA and to map to a region corresponding to the large ribosomal RNA coding region. The DNA plasmid was not transmitted into sexual (ascospore) progeny, irrespective of whether the diseased isolate acted as the female or male parent. Transmission of the disease to healthy, plasmid-free, ''recipient'' isolates by hyphal anastomosis was not accompanied by transfer of mitochondrial DNA or DNA plasmid from the diseased ''donor'' isolate, but resulted in de-novo generation of different plasmids, derived from the recipient's mitochondrial DNA.