MATERNAL INHERITANCE AND DIVERSITY OF MITOCHONDRIAL-DNA IN THE CHESTNUT BLIGHT FUNGUS, CRYPHONECTRIA-PARASITICA

The inheritance of mitochondrial DNA (mtDNA) in the chestnut blight fu ngus, Cryphonectriaparasitica, was investigated with laboratory crosse s and progeny from perithecia collected from a natural population. In a reciprocal cross, mtDNA haplotypes, determined from restriction frag ment length polymorphisms (RFLPs), were inherited only from maternal p arents. Another lab cross, in which the maternal strain was not known, showed uniparental inheritance for 43 ascospore progeny. All 87 proge ny from eight perithecia collected in the field showed uniparental inh eritance of mtDNA haplotypes identical to the maternal (canker) isolat es. These data strongly support the hypothesis that mtDNA is maternall y inherited in C. parasitica. In samples from three populations of C. parasitica, mtDNA haplotypes were highly diverse. Estimates of haploty pic diversity were high, ranging from 0.832 to 0.968 (maximum diversit y is 1.0 when all individuals have unique haplotypes). The possible ca uses of hypervariability in mtDNA are discussed.