Submitted to: British Mycological Society Annual International Symposia Series
Publication Type: Abstract Only
Publication Acceptance Date: September 13, 1997
Publication Date: N/A
Technical Abstract: The mitochondrial genomes of fungi are relatively small, usually circular molecules that can be purified easily, and are usually transmitted intact from generation to generation so are ideal for analyzing migration events. Mitochondrial genomes contain both variable and highly conserved regions so are useful for analyses at many phylogenetic levels. Fungal mtDNAs have a high AT content relative to the nuclear genomes which allows them to be purified easily in CsCl gradients. RFLP variation then can be analyzed by direct visual inspection of agarose gels. Digestion of total genomic DNAs with restriction enzymes that cleave at GC-rich, four-base recognition site chop the nuclear DNA into small fragments that run at the edge of a gel but leave the mtDNA relatively intact. This allows mtDNA variation to be assessed without purification. Southern analysis also can be performed using cloned fragments of mtDNA as probes. These techniques permit easy identification of mtDNA haplotypes but should be augmented with restrictio site mapping to reduce errors. Sequencing of mtDNA genes can be performed using universal primer sets. Sequence data can be used to develop PCR-based methods of mtDNA analysis. Phylogeography is an attempt to unite population genetics with phylogenetics and is particularly appropriate for mtDNA analyses. Mitochondrial phylogeography of the potato late blight pathogen, Phytophthora infestans, confirmed the panglobal distribution of a single clonal lineage, and also identified a probable secondary center of diversity in northern Mexico. Analyses of the complete mtDNA sequence of P infestans revealed several errors in previous interpretations of RFLP data. A comparison of the advantages/disadvantages of mtDNA versus isozyme and DNA fingerprint analyses will be presented.