title: Single nucleotide polymorphisms reveal multiple introductions into France of Plasmopara halstedii, the plant pathogen causing sunflower downy mildew.
abstract: Plasmopara halstedii, the causal agent of sunflower downy mildew, displays a gene-for-gene interaction with its host plant, Helianthus annuus and other species of the genus. Monitoring of the evolution of virulent races in France over a 19-year period led to the identification of 14 different races (or pathotypes). Twelve expressed sequence tag (EST)-derived markers displaying SNPs and insertion-deletion variations have recently been identified in P. halstedii. We used these markers to study the genetic structure and the evolution of sunflower downy mildew races. Bayesian assignment analysis identified three genetically differentiated groups of isolates organized around the first three races described in France. Strong genetic substructuring according to geographic origin of races was observed, confirming that these three groups corresponded to three separate introductions into France of isolates with different genetic and phenotypic backgrounds. Our results suggest that multiple introductions of P. halstedii isolates may have provided the raw material for more complex processes in the evolution of races, such as recombination between races or clonal evolution through mitotic instability.
authors.affiliation: INRA, Institut des Sciences de la Vigne et du Vin, UMR 1065 Santé Végétale (INRA-ENITAB), Centre de Recherche Bordeaux-Aquitaine, BP 81, 33883 Villenave d'Ornon cedex, France. delmotte@bordeaux.inra.fr
authors.forename: François
authors.initials: F
authors.lastname: Delmotte
authors.forename: Xavier
authors.initials: X
authors.lastname: Giresse
authors.forename: Sylvie
authors.initials: S
authors.lastname: Richard-Cervera
authors.forename: Jessica
authors.initials: J
authors.lastname: M'baya
authors.forename: Felicity
authors.initials: F
authors.lastname: Vear
authors.forename: Jeanne
authors.initials: J
authors.lastname: Tourvieille
authors.forename: Pascal
authors.initials: P
authors.lastname: Walser
authors.forename: Denis Tourvieille
authors.initials: DT
authors.lastname: de Labrouhe
mesh_terms: D005075:Biological Evolution; D005602:France; D005838:Genotype; D006368:Helianthus / Q000382:microbiology*; D009868:Oomycetes / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011157:Population Dynamics