MITOCHONDRIAL PLASMIDS OF THE GAEUMANNOMYCES-PHIALOPHORA COMPLEX AND THEIR DETECTION BY PRIMED, IN-SITU FLUORESCENCE LABELING

Double-stranded, linear DNA mitochondrial plasmids were detected in mo st Gaeumannomyces graminis var. tritici and var. avenae isolates, but were infrequently detected in G. graminis var. graminis, and only dete cted once in other Gaeumannomyces or Magnaporthe species. Plasmids wer e 4-11 kb and were apparently blocked at their 5' termini, as they wer e resistant to 5' --> 3' exonuclease digestion. Two plasmids that shar ed homology were further characterized. Apparently they were not deriv ed from the mitochondrial or nuclear genomes as they did not hybridize strongly to them. An internal fragment was cloned from one plasmid an d used as a primer for primed, in situ labeling with cryosectioned hyp hae. Plasmid-bearing strains had fluorescent signal in a pattern expec ted of a mitochondrial location for plasmids, whereas plasmid-less str ains did not fluoresce. This is the first use of cryosectioned hyphae and mitochondrial probes with in situ fluorescence labeling in fungi. (C) 1995 Academic Press, Inc.