Abstract
Domestication has led to profound phenotypic changes in crop species, leading to the emergence of "domestication syndromes". Adaptation of cultivated species to crop conditions (monospecific populations, high densities, high input levels) has led to individuals over-investing in competition for resources, to the detriment of group productivity. Although intraspecific competition in crops has been a central topic for breeders and agronomists since the mid-twentieth century, evolution of competitive ability in cultivated species is still poorly understood. The general aim of this thesis is to assess how domestication and modern breeding have modulated the ecological strategies of durum wheat and its ability to compete. Using a functional approach, we characterized the above-ground and below-ground morphology of a panel of genotypes from a series of domestication in durum wheat, ranging from its wild form to modern varieties. This enabled us to show that the phenotypic space of this species is structured by the same compromises as those described at the interspecific level. These results suggest that functional trade-offs are maintained at the intraspecific level despite the effect of artificial selection. We then assessed the response to competition of genotypes from the wheat domestication series. This work showed that the domesticated forms performed better in competition than their wild ancestors, despite a lower plasticity of traits. Finally, we showed that biomass responses to density increase were similar between the different stages of the durum wheat domestication series. In parallel, we showed that the allometric relationships between vegetative biomass and reproductive biomass did not vary between compartments despite major phenotypic changes. This thesis improves our understanding of the effects of domestication and modern breeding on the ecology of a field crop species. The study of ecological strategies and plant-plant interactions within cultivated species opens up interesting opportunities for varietal improvement and avenues for improving crop performance.