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Molecular Epidemiology of White Pine Blister Rust: Recombination and Spatial Distribution

July 2005 , Volume 95 , Number  7
Pages  793 - 799

R. C. Hamelin , M. Allaire , M.-J. Bergeron , M.-C. Nicole , and N. Lecours

Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Quebec, G1V 4C7 Canada

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Accepted for publication 4 March 2005.

Multilocus haplotypes (MLHs) were derived for the spermogonial (monokaryotic haploid) stage of Cronartium ribicola, the causal agent of white pine blister rust. Six random amplified polymorphic DNA loci and three single-strand conformational polymorphism markers were analyzed for 246 rust samples collected from two heavily infected white pine plantations. All cankers sampled were spatially located within the plantations. The hypothesis that spores are not locally disseminated was supported by the absence of any spatial clustering in the distribution of the MLHs. A large number of MLHs was found at both sites and the haplotypic diversity was close to the maximum (one) in both populations. All measures of recombination were not different from expectations under a scenario of sexual recombination. Genetic differentiation between the two sites was very low (θ = 0.023), yet it was significantly different from zero (P < 0.01). This analysis is in agreement with a scenario of extensive sexual recombination followed by some long-distance dispersal.

Additional keywords: genetic diversity .

© 2005 The American Phytopathological Society