Partitioning and distribution of RAPD variation in a set of populations of the Medicago sativa complex

Lucerne (Medicago sativa) is a major perennial forage legume and includes two main sub-species. The variation available within a group of 26 tetraploid populations of this complex was investigated with random amplified polymorphic DNA (RAPD) markers. Thirty seedlings per population were analysed. Twenty-nine reproducible markers, 24 being polymorphic, were obtained with four primers. The variation partitioning was studied using the AMOVA technique. The genetic variation proved to be nearly equally distributed within and between populations. The between-population variation was further partitioned between groups (falcata, Flemish, mediterranean) and between populations within groups. The latter source of variation was the major one. Although this study included a sub-species level, the within-population variation was very large probably due to the outcrossing reproduction and the tetraploidy. A similar approach was used to distinguish varieties and proved to be very efficient. The within-population dissimilarity indices were very variable according to the populations; the falcata and Flemish-type materials showed on average a larger within-population dissimilarity. The between-population dissimilarities were calculated and a dendrogram was drawn. This made it possible to separate the populations belonging to the two sub-species and the populations of subspecies sativa largely introgressed by falcata. The relationships among the sativa populations partly fitted with the known origin of the material or with their agronomic behaviour.