Le contournement de résistance par Melampsora Larici-populina l'agent de la rouille du peuplier : impact démographique et déterminisme génétique

Abstract : Melampsora larici-populina is a pathogenic fungus responsible of poplar leaf rust, causing severe damages in plantations worldwide. Almost all poplar resistances deployed so far in France have been overcome and a major event that occurred in 1994 with the breakdown of resistance R7 mostly used in poplar cultivation. In order to identify candidate genes linked to pathogenicity, I conducted a comparative genomics study based on the sequencing of 15 isolates. This analysis revealed polymorphism patterns correlated to the distribution of virulences among isolates while the necessity of a population genetics study. I then analyzed the genetic structure of a comprehensive collection of 600 isolates of M. larici-populina sampled from 1992 to 2012. This analysis demonstrated the major impact of the R7 breakdown on populations. Finally, I conducted a population genomics analysis to obtain a demographic scenario describing the historical links between populations and to identify genomic regions under selection. This analysis is based on the Illumina sequencing of 86 isolates in four key populations identified by the population genetic analysis. Over 1,000,000 polymorphic positions were identified. The best demographic scenario was assessed using Approximate Bayesian Computation algorithms based on coalescent simulations. Using this demographic scenario, I computed the confidence interval of several population genetic indices. This genome scan analysis was performed on the 86 genomes using this same indices and revealed 20 genomic regions containing 14 genes potentially involving in the resistance 7 breakdown
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Antoine Persoons. Le contournement de résistance par Melampsora Larici-populina l'agent de la rouille du peuplier : impact démographique et déterminisme génétique. Sciences agricoles. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0176⟩. ⟨tel-01754606⟩

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