Diversité génétique des traits racinaires chez les Vitis spp. et potentiel pour l'innovation variétale des porte-greffes de vigne adaptés à la sécheresse

Climate change impose to wine industry to adapt to drought conditions. One of the levers for action is to diversify the range of suitable rootstocks, as the root system plays a key role in how plants respond to water shortages, through its development and its ability to acquire resources from the soil. However, identifying root traits that promote drought tolerance and can be integrated into a genetic improvement program remains an unresolved issue, particularly for perennial species such as vines. This lack of knowledge is due in particular to the time-consuming nature of root phenotyping and the limitations of high-throughput phenotyping. The latter is essential for estimating the genetic variability of root traits in a representative manner across large populations. Nevertheless, a better understanding of the genetic diversity of the root systems of drought-adapted wild Vitis species is essential to inform programs for the development of vine rootstocks adapted to future environments.The aim of this thesis is to quantify the inter- and intraspecific genetic variation of root traits in wild Vitis spp., establish their link with responses to drought, and identify proxies to facilitate their incorporation into rootstock selection schemes.To this end, a panel of 50 accessions, including 12 wild species, was studied in the form of cuttings or grafted with Floréal, through two experiments subjected to water deficit. These experiments made it possible to evaluate aerial responses during water deficit, as well as to characterize the root system at the morphological, functional, anatomical, and metabolomic levels. Multivariate and univariate approaches were used to study the link between genetic variation in root traits and responses to drought. The study of metabolism explored biomarkers for predicting root traits. In addition, the covariation between metabolism and root traits was studied, revealing a wider variation in metabolism in response toenvironmental factors, though this trend varies between species. Finally, an experiment conducted in hydroponics and sand enabled us to evaluate the genetic diversity of traits related to the dynamics of early root system establishment. This complementary experiment enabled us to evaluate the phenotypic plasticity of root morphology traits in response to the growing medium and to test their stability during plant development.These results will enable us to characterise root strategies related to drought responses in a panel of natural diversity and thus to evaluate their potential in vine rootstock selection programmes.