Author
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Aime, Mary |
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Submitted to: Mycoscience
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/20/2006 Publication Date: 6/25/2006 Citation: Aime, M.C. 2006. Toward resolving family-level relationships in rust fungi (Uredinales). Mycoscience 47(3):112-122. Interpretive Summary: Rust fungi are a very large and diverse group of parasites that attack plants and annually cause billions of dollars of crop and forest losses in the United States and throughout the world. Non-native rust fungi threaten U.S. borders as the cause of invasive diseases. Others may have potential use as biological control organisms for noxious weeds. A major problem facing U.S. agriculture, forestry, and plant health inspectors is that these disease-causing fungi are microscopic and very difficult to identify and classify. In this paper DNA sequence data from two different genes were examined and compiled for over 400 species of rust fungi. It was ascertained that older classifications that relied on physical characteristics do not accurately reflect the true family relationships of these pathogens, and new relationships are discovered. These results are significant because they provide the means for more accurately identifying and predicting the behavior of new and established rust threats. Consequently this research will be used by agronomists, plant pathologists, other scientists, and plant regulatory and quarantine personnel who need to know how to identify rust fungi, what plant hosts they grow on, and make predictions regarding their host plants, pathogenicity, and distribution. Technical Abstract: Rust fungi (Basidiomycota, Uredinales) consist of > 7000 species of obligate plant pathogens that possess some of the most complex life cycles in the Eumycota. Traditionally, phylogenetic inference within the Uredinales has been hampered by few synapomorphic characters and incomplete life cycle and host-specificity data. The application of modern molecular characters to rust systematics has been limited and current contradictions in rust systematics, especially in the deeper nodes, have not yet been resolved. In this study, two nuclear rDNA genes (18S and 28S) were examined across the breadth of the Uredinales to resolve some systematic conflicts and provide a framework for further studies of the group. Of the thirteen rust families most widely accepted, seven are supported in full or in part (Pucciniaceae, Phragmidiaceae, Phakopsoraceae p.p., Raveneliaceae, Mikronegeriaceae, Melampsoraceae, Pucciniastraceae), four are redundant (Chaconiaceae, Pucciniosiraceae, Cronartiaceae, Chrysomyxaceae), and the status for two (Uropyxidaceae and Pileolariaceae) cannot be resolved with this study. It is concluded that morphology alone is a poor predictor of rust relationships at most levels and morphology-based classifications and species-delimitations appear obsolete. On the other hand, host selection has played a significant role in rust evolution. |
