| Summary: | Texte intégral accessible uniquement aux membres de l'Université de Lorraine Since 25 years, the poplar rust fungus, Melampsora larici-populina, is responsible of the most important phytosanitary problems in poplar cultivation. Direct study of biological characteristics, such as dispersal distances or relative importance of sexual vs. asexual reproduction, is often difficult in such pathogenic fungi. A way to infer these characteristics is the use of molecular markers. Fifteen microsatellite markers were developed in order to perform population genetics studies of M. larici-populina at different spatial scales. At a fine scale (leave, twig, tree, site) a great genotypic diversity was observed, as well as a significant structure at the site and tree scales. At a regional scale, the study of M. larici-populina populations in the Durance River valley corridor revealed the co-occurrence of two epidemics, in the wild and in the cultivated compartment. Furthermore, exchanges from cultivated stands to wild stands were shown. The Long distance migration capacity of M. larici-populina was assessed by studying eight European populations and two populations recently founded in Iceland and Canada. European populations exhibited an isolation by distance pattern, whereas non-European populations appeared to result from a long distance dispersal of a limited number of individuals. L'agent de la rouille du peuplier, Melampsora larici-populina, est l'agent pathogène qui pose le plus de problèmes phytosanitaires dans la populiculture européenne depuis ces 25 dernières années. L'étude directe de caractéristiques biologiques, tels que la distance de dispersion ou l'importance relative de la reproduction sexuée et asexuée, est souvent complexe chez ce type de champignons phytopathogènes. L'apport de l'étude de marqueurs moléculaires peut donc se révéler essentiel dans l'estimation de tels paramètres. Quinze marqueurs microsatellites ont été développés afin de réaliser des études de génétique des populations de M. larici-populina ...
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