Résumé
Landraces have a large diversity that could help to cope with climatic change and low input agriculture. A novel DNA pooling strategy was implemented to identify promising maize landraces and genomic regions to enlarge the genetic diversity of modern varieties. We assessed the genome-wide diversity of landraces at worldwide and regional levels by genotyping with SNP array the DNA pools of 156 American and European landraces as well as 264 French landraces that have been evaluated for different agronomic traits. They were compared to elite cultivars produced across 20th century, represented by 327 inbred lines. We identified several genomic regions involved in agronomic traits, environmental adaptation, notably in tolerance to abiotic and biotic stresses by either detecting selective footprints or by performing association studies with both environmental variables and agronomic traits. Allelic variation at Vgt3 locus in French landraces is both associated with flowering time variation and altitude in French landraces from Pyrennean Mountain suggesting that Vgt3 lead to adaptation to altitude in Pyrenean Mountain by shortening flowering time. Promising landraces were then identified by estimating their genomic contribution to a collection of 327 inbred lines. Most landraces do not have closely related lines while 10 landraces have a lot and cumulated half of the total contribution to inbred lines. We applied a genomic selection approach to identify promising landraces based on prediction of different agronomic traits. Our approach opens an avenue for the identification of promising landraces for pre-breeding.