Canadian Forest Service Publications

Signatures of post-gacial genetic isolation and human-driven migration in the Dothistroma needle blight pathogen in western Canada. 2020. Capron, A.; Feau, N.; Heinzelmann, R.; Barnes, I.; Benowicz, A.; Bradshaw, R.E.; Dale, A.; Lewis, K.J.; Owen, T.J.; Reich, R.; Ramsfield, T. D.; Woods, A.J.; Hamelin, R.C. Phytopathology 111(1):116-127.

Year: 2020

Issued by: Northern Forestry Centre

Catalog ID: 40706

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1094/PHYTO-08-20-0350-FI

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Many current tree improvement programs are incorporating assisted gene flow strategies to match reforestation efforts with future climates. This is the case for the lodgepole pine (Pinus contorta var. latifolia), the most extensively planted tree in western Canada. Knowledge of the structure and origin of pathogen populations associated with this tree would help improve the breeding effort. Recent outbreaks of the Dothistroma needle blight (DNB) pathogen Dothistroma septosporum on lodgepole pine in British Columbia and its discovery in Alberta plantations raised questions about the diversity and population structure of this pathogen in western Canada. Using genotyping-by-sequencing on 119 D. septosporum isolates from 16 natural pine populations and plantations from this area, we identified four genetic lineages, all distinct from the other DNB lineages from outside of North America. Modeling of the population history indicated that these lineages diverged between 31.4 and 7.2 thousand years ago, coinciding with the last glacial maximum and the postglacial recolonization of lodgepole pine in western North America. The lineage found in the Kispiox Valley from British Columbia, where an unprecedented DNB epidemic occurred in the 1990s, was close to demographic equilibrium and displayed a high level of haplotypic diversity. Two lineages found in Alberta and Prince George (British Columbia) showed departure from random mating and contemporary gene flow, likely resulting from pine breeding activities and material exchanges in these areas. The increased movement of planting material could have some major consequences by facilitating secondary contact between genetically isolated DNB lineages, possibly resulting in new epidemics.

Plain Language Summary

This manuscript outlines a population genetics study of Dothistroma septosporum, an important pathogen of pines in British Columbia and Alberta. It was found that four genetic lineages were present in the 16 populations of the pathogen that were assessed, and the population in Alberta was most closely related to the population in Prince George, BC. It is hypothesized that the pathogen was introduced into Alberta through the movement of infected pine material used by breeders. This paper reinforces that caution must be observed when moving plant material as it is possible to also move plant pathogens accidentally.