Structuration of alfalfa genetic diversity using agronomic and morphological characteristics. Relationship with RAPD markers

Morphological and agronomic characteristics were studied on 46 tetraploid populations of Medicago sativa ssp.sativa and ssp.falcata over three growing cycles in a spaced plant experimental design.The genetic diversity was analysed using principal component analysis and clusters were defined on the Euclidean distances.The wild populations of both subspecies were clustered together because of their fall dormancy and their prostrate growth habit.Among the cultivated populations, genetic differentiation in two major clusters corresponding to the Mediterranean types and the Nordic types was found.A population from Turkey showed a behaviour intermediate between the two groups with a vigorous growth in the different seasons and high seed production.The relationship between the Euclidean distance based on the morphological characteristics and the distance on the RAPD markers was analysed on 26 populations with a generalization of the Mantel statistics.It was shown that the relationship was significant for the major groups of variation, i.e. at the subspecies level, the relationship being not significant for the populations within the groups.