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

The inheritance of mitochondrial DNA (mtDNA) in the chestnut blight fungus, Cryphonectriaparasitica, was investigated with laboratory crosses and progeny from perithecia collected from a natural population. In a reciprocal cross, mtDNA haplotypes, determined from restriction fragment length polymorphisms (RFLPs), were inherited only from maternal parents. Another lab cross, in which the maternal strain was not known, showed uniparental inheritance for 43 ascospore progeny. All 87 progeny from eight perithecia collected in the field showed uniparental inheritance of mtDNA haplotypes identical to the maternal (canker) isolates. These data strongly support the hypothesis that mtDNA is maternally inherited in C. parasitica. In samples from three populations of C. parasitica, mtDNA haplotypes were highly diverse. Estimates of haplotypic diversity were high, ranging from 0.832 to 0.968 (maximum diversity is 1.0 when all individuals have unique haplotypes). The possible causes of hypervariability in mtDNA are discussed.