Potentiel évolutif et déterminisme génétique de caractères d’agressivité et morphologiques de l’agent de la rouille du peuplier, Melampsora larici-populina

Abstract : To control plant pathogens, breeding resistant plants is the most cost-effective and ecological strategy. Quantitative resistances, which are based on complex plant mechanisms, are known to be exposed to erosion through an increase of pathogens aggressiveness. Through the study the poplar – poplar rust (Melampsora larici-populina) pathosystem, this work aims to estimate the evolutionary potential of aggressiveness and morphological traits using quantitative genetic approaches and to identify molecular bases through genome-wide association study. To estimate plasticity, heritability, and trade-offs for a set of quantitative traits, we precisely measured their variation in four contrasted pathogen populations. It appeared that spore volume is highly heritable and evolved rapidly. In planta mycelium quantity is also heritable but constant because of stabilizing selection occurring in the studied populations. Latent period, lesion size and sporulation rate exhibit low heritability, which explains the absence of evolution during the studied time period. Traits involved in the sporulating function seem to be the most plastic ones along a leaf maturity gradient. However, the lack of evidence of trade-offs did not allow us to identify aggressiveness traits that would be the best targets for the construction of durable resistance in poplar. No genetic underpinning has been found for quantitative traits, but we have identified a potential avirulence locus (Avr7), opening the way for its functional characterization
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Agathe Maupetit. Potentiel évolutif et déterminisme génétique de caractères d’agressivité et morphologiques de l’agent de la rouille du peuplier, Melampsora larici-populina. Phytopathologie et phytopharmacie. Université de Lorraine, 2018. Français. ⟨NNT : 2018LORR0202⟩. ⟨tel-02075708⟩

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