Molecular Systematic Investigation of Rust Fungi Associated with Pinaceae

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The rust fungi are plant pathogens that are responsible for several economically important diseases of pines and their conifer relatives. The taxonomy and phylogeny of rust fungi are controversial because the organisms are small, with few discernible morphological differences, and they have complex life histories with several spore-bearing stages. Dr. Thomas Bruns of the University of California-Berkeley will use modern molecular techniques to investigate evolutionary relationships among rust fungi of the major family Melampsoraceae. He has developed methods that allow specific amplification of DNA from small amounts of fungal material, even from preserved specimens, and with this refinement plant-host DNA will no longer interfere with the study of the fungus. Selected nuclear and mitochondrial genes of numerous species of rust fungi will be analyzed for their nucleotide sequences, and these will be compared using computer programs to generate a likely phylogenetic framework for related species. The phylogeny thus constructed for the fungi will then be compared to current notions of pine species phylogeny to test the idea that fungal parasites and host pines have evolved in association ("coevolution") through geological time. In addition, the molecular analyses will provide unique genetic markers of individual rust-fungus species, valuable for purposes of accurate identification in other taxonomic and ecological studies.