Hanna, J.  2004.  Genetic relationships among Armillaria species - root pathogens and saprophytes of forest ecosystems.  Plant Science Seminar.  University of Idaho.  04.22.2004.

Abstract:

Of particular concern to forest managers of the inland northwestern United States is the root rot pathogen Armillaria ostoyae. This pathogen causes tree mortality and growth reduction on a variety of woody plant hosts. Using a direct-PCR method, sequences of the nuclear ribosomal DNA (i.e., large subunit, internal transcribed spacer, 5.8S, and intergenic spacer) were obtained from ten North American Armillaria species. Phylogenetic analyses using Bayesian methods were used to compare A. ostoyae with other Armillaria species in North America. Pathogenic species A. mellea and A. tabescens were found to be distantly related to A. ostoyae and seven other Armillaria species. Additional analyses centered on A. ostoyae within the western United States defined several groups of A. ostoyae. Analysis of A. ostoyae from outside the western United States indicates the presence of a circumboreal group of A. ostoyae that also occurs in Utah. Phylogeographically unique groups were also present in the Rocky Mountain and Pacific Northwest regions. Other Armillaria species were used as outgroups to examine evolutionary relationships among the groups of A. ostoyae. The occurrence of these groups allows inferences about paleogeographic and paleoclimatic influences on phylogeography of A. ostoyae. Additionally, hybridization has occurred among groups that may have been previously isolated for millions of years. Hybridization has potential implications on species evolution and could contribute to variation in pathogenicity and virulence.

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