De la génétique des populations à la gestion durable des résistances : intérêt de l'étude des populations sauvages des pathogènes des cultures. Cas de deux nématodes à kystes et de leur hôte sauvage commun

Abstract : The sustainable management of genetic resistances to crop pathogens needs to consider their evolutionary potential. The evolutionary potential results both from the evolutionary history and the current population dynamics of pathogens, which can be affected by human activities occurring in agro-ecosystems. Therefore, they should be described and evaluated on wild pathogen populations free of human-mediated disturbances. The aim of this work is twofold (1) assessing the evolutionary history of two cysts nematodes, Heterodera schachtii and Heterodera betae, and their common wild host, Beta vulgaris ssp. maritima, in wild populations sampled on the coast from the South of Spain to Sweden; (2) investigating at a fine spatial scale the population genetic structure of H. schachtii .Results show that the colonization of the Atlantic coastline by the two nematodes was probably influenced by climatic fluctuations occurring since the Last Glacial Maximum, along with marine currents. Phylogeographical patterns of H. schachtii and the host-plant suggest a non-shared evolutionary history, which contrasts with the coastal recolonization of Europe observed in H. betae. The fine-scale study evidenced that wild populations of H. schachtii are genetically sub-structured at the level of the host plant, strongly isolated and characterized by small effective population sizes. All these results are discussed in the framework of the sustainable management of nematodes populations in cultivated fields.
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Cécile Gracianne. De la génétique des populations à la gestion durable des résistances : intérêt de l'étude des populations sauvages des pathogènes des cultures. Cas de deux nématodes à kystes et de leur hôte sauvage commun. Sciences agricoles. Agrocampus Ouest, 2015. Français. ⟨NNT : 2015NSARA074⟩. ⟨tel-01366314⟩

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