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Genetic Diversity and the Presence of Two Distinct Groups in Ophiostoma clavigerum Associated with Dendroctonus ponderosae in British Columbia and the Northern Rocky Mountains

First and fourth authors: Department of Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada; second author: Forest Pest Biotechnology, Laurentian Forestry Centre, Natural Resources Canada, 1055 rue du PEPS, Quebec City, QC, G1V 4C7, Canada; third author: Department of Ecosystem and Conservation Science, College of Forestry and Conservation, University of Montana, Missoula 59812.

The sapstaining fungal pathogen Ophiostoma clavigerum is associated with the mountain pine beetle (Dendroctonus ponderosae), which is currently the most destructive forest pest in North America. The genetic diversity of O. clavigerum populations collected from five sites in Canada and two sites in the United States was estimated with amplified fragment length polymorphism (AFLP) analysis. Genomic DNA from 170 O. clavigerum isolates was digested with EcoRI and PstI and amplified with six primer sets. A total of 469 AFLP markers consisting of 243 monomorphic and 226 polymorphic loci were scored. The overall genetic diversity of the O. clavigerum population was low (Hs = 0.0531) and the differentiation of the seven O. clavigerum populations was moderate (Φ = 0.143). Genetic distances among the populations were not significantly correlated with geographic distance (r = 0.3235, P = 0.074). Two genetically distinct groups in the O. clavigerum populations were shown by unique AFLP profiles and the unweighted pair group method with arithmetic averages. Further work to characterize biological differences between the two groups will be needed to confirm whether cryptic species are present in the O. clavigerum population.