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Genetic signature of a range expansion and leap-frog event after the recent invasion of Europe by the grapevine downy mildew pathogen Plasmopara viticola

Authors

  • Michael C. Fontaine,

    Corresponding author
    1. Ecologie, Systématique et Evolution, UMR 8079 Université Paris Sud Laboratoire Ecologie, Systematique et Evolution, Orsay Cedex, France
    2. Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Paris Cedex 5, France
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  • Fréderic Austerlitz,

    1. Ecologie, Systématique et Evolution, UMR 8079 Université Paris Sud Laboratoire Ecologie, Systematique et Evolution, Orsay Cedex, France
    2. Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Paris Cedex 5, France
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  • Tatiana Giraud,

    1. Ecologie, Systématique et Evolution, UMR 8079 Université Paris Sud Laboratoire Ecologie, Systematique et Evolution, Orsay Cedex, France
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  • Frédéric Labbé,

    1. Ecologie, Systématique et Evolution, UMR 8079 Université Paris Sud Laboratoire Ecologie, Systematique et Evolution, Orsay Cedex, France
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  • Daciana Papura,

    1. INRA, UMR1065 Santé et Agroécologie du Vignoble, ISVV, Villenave d'Ornon Cedex, France
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  • Sylvie Richard-Cervera,

    1. INRA, UMR1065 Santé et Agroécologie du Vignoble, ISVV, Villenave d'Ornon Cedex, France
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  • François Delmotte

    1. INRA, UMR1065 Santé et Agroécologie du Vignoble, ISVV, Villenave d'Ornon Cedex, France
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Abstract

Biologic invasions can have important ecological, economic and social consequences, particularly when they involve the introduction and spread of plant invasive pathogens, as they can threaten natural ecosystems and jeopardize the production of human food. Examples include the grapevine downy mildew, caused by the oomycete Plasmopara viticola, an invasive species native to North America, introduced into Europe in the 1870s. We investigated the introduction and spread of this invasive pathogen, by analysing its genetic structure and diversity in a large sample from European vineyards. Populations of P. viticola across Europe displayed little genetic diversity, consistent with the occurrence of a bottleneck at the time of introduction. Bayesian coalescent analyses revealed a clear population expansion signal in the genetic data. We detected a weak, but significant, continental-wide population structure, with two geographically and genetically distinct clusters in Western and Eastern European vineyards. Approximate Bayesian computation, analyses of clines of genetic diversity and of isolation-by-distance patterns provided evidence for a wave of colonization moving in an easterly direction across Europe. This is consistent with historical reports, first mentioning the introduction of the disease in Bordeaux vineyards (France) and sub-sequently documenting its rapid spread across Europe. This initial introduction in the west was probably followed by a ‘leap-frog’ event into Eastern Europe, leading to the formation of the two genetic clusters we detected. This study shows that recent population genetics methods within the Bayesian and coalescence frameworks are extremely powerful for increasing our understanding of pathogen population dynamics and invasion histories.

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