title: Genotypic diversity and migration patterns of Phytophthora infestans in the Nordic countries.
abstract: In this study we investigated the genotypic diversity and the migration patterns of Phytophthora infestans in the Nordic countries. Isolates of P. infestans from outbreaks in 43 fields sampled in 2008 were collected using stratified sampling with country, field, and disease foci as the different strata. Microsatellites were used as markers to determine the genotypic variation in the sampled material. The results show a high genotypic variation of P. infestans in the Nordic countries with most of the genotypes found only once among the collected isolates. The major part of the genotypic variation was observed within the fields, with low differentiation between the fields. The observed low association of alleles among loci is consistent with frequent sexual reproduction of P. infestans in the Nordic countries. Coalescence analyses did not support a single common population for the four countries, thus indicating some degree of geographic differentiation. The analyses of migration patterns showed differing levels of gene flow among the Nordic countries. No correlation between migration rates and geographical distance could be seen. This could be explained by different degrees of genetic similarity between the pathogen populations in the different countries.
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, SE-75007 Uppsala, Sweden.
authors.forename: Lina
authors.initials: L
authors.lastname: Sjöholm
authors.forename: Björn
authors.initials: B
authors.lastname: Andersson
authors.forename: Nils
authors.initials: N
authors.lastname: Högberg
authors.forename: Anna-Karin
authors.initials: AK
authors.lastname: Widmark
authors.forename: Jonathan
authors.initials: J
authors.lastname: Yuen
mesh_terms: D004271:DNA, Fungal / Q000235:genetics; D014644:Genetic Variation; D018895:Microsatellite Repeats; D058974:Phylogeography; D055750:Phytophthora infestans / Q000145:classification* / Q000302:isolation & purification*; D010935:Plant Diseases / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal
keywords: Effective population size; Potato late blight; Sexual reproduction; Simple-sequence repeats (SSR); Stratified sampling