Population Genomic Analyses Reveal Connectivity via Human-Mediated Transport across Plantations in North America and an Undescribed Subpopulation of .

Domestication of plant species has affected the evolutionary dynamics of plant pathogens in agriculture and forestry. A model system for studying the consequences of plant domestication on the evolution of an emergent plant disease is the fungal pathogen . This ascomycete causes leaf spot and stem canker disease of spp. and their hybrids. A population genomics approach was used to determine the degree of population structure and evidence for selection on the North American population of . In total, 122 samples of the fungus were genotyped identifying 120,016 single-nucleotide polymorphisms after quality filtering. In North America, has low to moderate degrees of differentiation among locations. Three main genetic clusters were detected: southeastern United States, midwestern United States and Canada, and a new British Columbia cluster (BC2). Population genomics suggest that BC2 is a novel genetic cluster from central British Columbia, clearly differentiated from previously reported from coastal British Columbia, and the product of a single migration event. Phenotypic measurements from greenhouse experiments indicate lower aggressiveness of BC2 on In summary, has geographic structure across broad regions indicative of gene flow among clusters. The interconnectedness of the North American populations across large geographic distances further supports the hypothesis of anthropogenic-facilitated transport of the pathogen.