Biological Invasions (2016) 18, 1781-1799

Monique L. Sakalidis, Nicolas Feau, Braham Dhillon and Richard C. Hamelin (2016)
Genetic patterns reveal historical and contemporary dispersal of a tree pathogen
Biological Invasions 18 (6), 1781-1799
Abstract: Sphaerulina musiva (Peck) Verkley, Quaedvlieg and Crous (syn = Septoria musiva Peck, Mycosphaerella populorum Thompson) is a pathogen of poplar that causes two distinct diseases, leaf spots and cankers. This pathogen co-evolved with Populus deltoides but recent reports have linked it to infections in planted stands of P. trichocarpa, P. balsamifera and their hybrids. Reports of S. musiva have mainly come from central and eastern US and eastern Canada, the assumed endemic range of the pathogen. S. musiva was detected for the first time in the Canadian provinces of British Columbia in 2006 and in Alberta in 2009. Our objectives were to determine the source of S. musiva in British Columbia and Alberta and examine the dispersal pathways of this pathogen across North America. For this task we sequenced eight genes and extracted single nucleotide polymorphisms on a geographically diverse set of 73 strains of S. musiva. Population structure and Approximate Bayesian Computation (ABC) analyses eliminated eastern Canada as a source for these introductions. Genetic diversity estimates and ABC analyses support an eastern US centre of origin for S. musiva and two waves of dispersal into Canada. The recently detected west Canadian populations appear to have received contributions from Saskatchewan (a western Canadian population) and also, in the case of British Columbia from the mid-west US populations. These results also reveal distinct eastern and western Canadian populations. Our analyses suggest that dissemination of the pathogen appears to be associated with the natural distribution of wild P. deltoides and more recently linked to anthropogenic activities. The most parsimonious explanation for the contemporary spread of S. musiva across the landscape is via infected plant material. Our analysis of the tree disease caused by S. musiva demonstrates that a population genetics approach is essential to reveal potential sources and patterns of spread of a pathogen.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Monique L. Sakalidis, Richard C. Hamelin

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sphaerulina musiva	Poplar/aspen (Populus)	Canada (east)
	Sphaerulina musiva	Poplar/aspen (Populus)	Canada (west)