Systematics and Evolution of Cenococcum Geophilum Fr.: An Old Asexual Lineage?

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9318119 Taylor Molecular methods of DNA analysis, including nucleotide sequencing and restriction enzyme mapping, are revolutionizing the study of fungal evolution and taxonomy. The most problematic groups of fungi, the asexual forms that do not undergo meiosis and do not form spores, are especially troublesome because it is morphological features of the spore-bearing structures that have traditionally served as characters for taxonomic identification and classification. Molecular data provide a solution to the dilemma. Postdoctoral associate Dr. Karen LoBuglio under the guidance of Dr. John Taylor at University of California-Berkeley is using modern molecular procedures in a novel attack on this problem, emphasizing the well-known mycorrhizal fungus Cenococcum geophilum, which has been found throughout the world but never with spores. Data from proteins and from nuclear ribosomal DNA will help determine the closest living phylogenetic relatives of this fungus in the ascomycete lineage; under molecular clock assumptions, these data will also suggest the time of origin of the taxon. Molecular data will also indicate the extent of genetic variation within local and regional populations of the fungus, and thereby test whether cryptic cellular processes of recombination might generate variation in what has been considered an asexual, dead-end mode of life. New DNA-based data from a widespread but asexual mycorrhizal fungus will help answer two important questions: the proper classification and phylogenetic position of Cenococcum geophilum and the possibility that asexual taxa of fungi are able to generate genetic variability, perhaps through cryptic cellular processes of recombination.