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Pressions de sélection exercées par les résistances génétiques du melon sur les populations d'Aphis Gossypii

Abstract : The adaptive response of pest populations to selection pressures exerted by agricultural activities determines the sustainability of control methods. In melon, the Vat gene that confers resistance to Aphis gossypii has been deployed for over 10 years, so there are fears it will be overcome. The challenge is to provide strategic elements to plant breeders, concerning the risk of development of virulent aphids, in order to develop new varieties with durable resistances. In the context of this PhD, we have: i) Estimated the available genetic diversity in populations of A. gossypii from different melon growing areas. The diversity is structured geographically. The great diversity observed in France would have its origine in part from the events of sexual reproduction, suggesting a high evolutionary potential of A. gossypii. ii) Estimated the selection pressure exerted by different resistance combinations (Vat gene and QTLs) on these populations. Population densities are lower on VatR plants than VatS plants and population genetic structure is altered in certain growing areas when the VatR gene is present. The clones multiplying on VatR plants have good fitness and the risk of their spreading is great. No effect of QTLs has been identified in the field. iii) Characterized the clones overcoming the VatR gene. Our results suggest that the adaptation of clones made either by alteration of the avirulence gene of aphids or by adaptation of aphids to resistance effectors. New strategies for Vat resistance management are proposed.
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Sophie Thomas. Pressions de sélection exercées par les résistances génétiques du melon sur les populations d'Aphis Gossypii. Sciences du Vivant [q-bio]. Université d'Avignon et des Pays de Vaucluse, 2011. Français. ⟨tel-02811117⟩

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