Résumé
Crop/weed gene flow is often of great concern for a better understanding of germplasm diversity. This paper provides an overview of the levels and partition of genetic diversity assessed between wild and cultivated populations of Medicago sativa L. in Spain for both molecular markers and agromorphological traits. We report that most wild populations preserve a great agronomic and morphological originality despite their occasional parapatry with cultivated forms and the occurrence of crop/weed gene flow in many locations. However, populations that display either a continuous range of intermediate plants between the typical wild and cultivated forms, or a mosaic of individuals that can be assigned to each gene pool respectively, were also identified. Providing that reproductive isolation is not strict, we hypothesise that contrasted selective pressure between wild and cultivated populations mainly accounted for the maintenance of their phenotypic integrity. (C) Inra/Elsevier, Paris