Résumé
Due to their local adaptation to contrasted environments, maize landraces are a valuable source of genetic diversity for facing climate change and low input agriculture challenges. High-throughput pool genotyping (HPG) is a cost-effective approach to genotype maize landraces and identify promising sources of alleles for tolerance to abiotic stress. We applied this approach to a panel of 626 European landraces from 9 genebanks to i) characterize genetic diversity and its structuration; ii) perform genomic prediction (GP) of both adaptive and agronomic traits, and iii) perform association studies to identify genomic regions involved in phenotypic variation and/or in environmental adaptation, using climatic variables of landraces collection sites. Landraces genetic diversity was structured according to their geographical and historical origin, human utilization, and environmental conditions .This genetic structuration had strong effects on agro-morphological traits. GP yielded high accuracy for phenotypic and for some climatic variables from landrace collection sites. This suggests that GP could be used to characterize large collection of landraces maintained in genebanks. It also suggests that the genomic composition of landraces has been strongly shaped by environmental conditions of their collection sites. Association studies with both traits and environmental variables allowed us to detect important genomic regions, as exemplified by known loci Vgt2 and Vgt3 for flowering time. Finally, we investigated how these detected genomic regions relate to environmental variables in a non-linear fashion using a gradient forest approach. We identified drastic change for specific alleles along environmental gradients, suggesting that this loci could play a role in local adaptation of landraces. The combination of eco-genetic and genomic prediction opens an avenue for accelerating the characterization and use of genetic resources for prebreeding, in the context of adaptation to future growing conditions.