title: Population history and pathways of spread of the plant pathogen Phytophthora plurivora.
abstract: Human activity has been shown to considerably affect the spread of dangerous pests and pathogens worldwide. Therefore, strict regulations of international trade exist for particularly harmful pathogenic organisms. Phytophthora plurivora, which is not subject to regulations, is a plant pathogen frequently found on a broad range of host species, both in natural and artificial environments. It is supposed to be native to Europe while resident populations are also present in the US. We characterized a hierarchical sample of isolates from Europe and the US and conducted coalescent-, migration, and population genetic analysis of sequence and microsatellite data, to determine the pathways of spread and the demographic history of this pathogen. We found P. plurivora populations to be moderately diverse but not geographically structured. High levels of gene flow were observed within Europe and unidirectional from Europe to the US. Coalescent analyses revealed a signal of a recent expansion of the global P. plurivora population. Our study shows that P. plurivora has most likely been spread around the world by nursery trade of diseased plant material. In particular, P. plurivora was introduced into the US from Europe. International trade has allowed the pathogen to colonize new environments and/or hosts, resulting in population growth.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Department of Biodiversity and Conservation Biology, Birmensdorf, Switzerland.
authors.forename: Corine N
authors.initials: CN
authors.lastname: Schoebel
authors.affiliation: USDA-ARS-Horticultural Crops Research Laboratory, Corvallis, Oregon, United States of America ; Department of Botany & Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Jane
authors.initials: J
authors.lastname: Stewart
authors.forename: Niklaus J
authors.initials: NJ
authors.lastname: Grünwald
authors.affiliation: USDA-ARS-Horticultural Crops Research Laboratory, Corvallis, Oregon, United States of America ; Department of Botany & Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Niklaus J
authors.initials: NJ
authors.lastname: Gruenwald
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Department of Biodiversity and Conservation Biology, Birmensdorf, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rigling
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Department of Biodiversity and Conservation Biology, Birmensdorf, Switzerland.
authors.forename: Simone
authors.initials: S
authors.lastname: Prospero
mesh_terms: D044822:Biodiversity; D014644:Genetic Variation; D006239:Haplotypes; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010802:Phylogeny; D010838:Phytophthora / Q000145:classification* / Q000235:genetics*; D010935:Plant Diseases / Q000469:parasitology; D010944:Plants / Q000469:parasitology*; D011157:Population Dynamics