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Adaptation des populations virales aux résistances variétales et exploitation des ressources génétiques des plantes pour contrôler cette adaptation

Abstract : Plants carrying major resistance genes have been widely used to fight against diseases. However, the pathogens ability to overcome the resistance after a few years of usage requires the search for efficient and durable resistances. The objectives of this thesis were (i) to identify plant genomic regions limiting pathogen evolution by inducing genetic drift effects and (ii) to study the impact of the evolutionary forces imposed by the plant on the pathogen ability to adapt to resistance, the goal being to further use these forces to limit pathogen evolution. The pepper (Capsicum annuum) – PVY (Potato virus Y) pathosystem has been mainly used to conduct these researches. Regarding the first objective, quantitative trait loci (QTL) were mapped on a biparental pepper population and through genome-wide association on a pepper core-collection. These approaches have allowed the detection of genomic regions on chromosomes 6, 7 and 12 controlling viral effective population size during the inoculation step. Some of these QTLs were common to PVY and CMV (Cucumber mosaic virus) while other were virus-specific. Moreover, the QTL detected on chromosome 6 colocalizes with a previously identified QTL controlling PVY accumulation and interacting with a QTL affecting the breakdown frequency of a major resistance gene. Regarding the second objective, a correlation analysis between the evolutionary forces imposed by the plant and an experimental estimation of the durability of a major resistance gene has been done. Experimental evolution of PVY populations on plants contrasted for the levels of genetic drift, selection and virus accumulation they imposed has also been performed. Both studies demonstrated that a plant inducing a strong genetic drift combined to a reduction in virus accumulation limits virus evolution and could even lead to the extinction of the virus population. These results open new perspectives to deploy plant genetic factors directly controlling pathogen evolutionary potential and could help to preserve the durability of major resistance genes.
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Lucie Tamisier. Adaptation des populations virales aux résistances variétales et exploitation des ressources génétiques des plantes pour contrôler cette adaptation. Sciences agricoles. Université d'Avignon et des Pays de Vaucluse, 2017. Français. ⟨tel-02791008⟩

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