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Influence des processus démographiques sur la structure et les caractéristiques génétiques des champignons phytopathogènes, cas de l'agent de la rouille du peuplier Melampsora larici-populina

Abstract : Many factors can impact the genetic structures and population dynamics of fungal plant pathogens. Here we illustrated some of them at different spatial scales for the poplar rust fungus Melampsora larici-populina. At the scale of France, two main genetic groups were found. The first one infects only wild hosts and results from natural evolution of rust populations. The second one was formed after the R7 resistance breakdown, which is carried by the cultivar ?Beaupré?. This group exhibited a high proportion of virulent 7 individuals and presented signs of selection and demographic expansion; these signs indicate the recent invasion of individuals from this group on both wild and cultivated poplars in the northern half of France. At a regional scale, we focused on a contact zone between the ?cultivated? and the ?wild? genetic groups, located in the Alps. Upstream the Durance River valley, the influence of landscape has been highlighted by the effect of the Ecrins range which protects the ?wild? group located on the east side from the invasion of individuals from the ?cultivated? group, which arise from the northwest. Downstream the valley the annual epidemic wave was shown to be composed of admixed individuals from ?wild? and ?cultivated? groups, originating from both sides of the Ecrins range. Lastly we assessed the genetic consequences of the colonization wave. We evidenced a gradual increase of genetic differentiation with the epidemic source and a loss of genetic diversity. This work highlights the need of combining population genetics and epidemiology to characterize demographic processes and their genetic consequences
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Constance Xhaard. Influence des processus démographiques sur la structure et les caractéristiques génétiques des champignons phytopathogènes, cas de l'agent de la rouille du peuplier Melampsora larici-populina. Biologie végétale. Université Henri Poincaré - Nancy 1, 2011. Français. ⟨NNT : 2011NAN10038⟩. ⟨tel-01746180⟩

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