ABSTRACT
The genus Medicago comprises more than 60 species, two-thirds being annuals and one-third being perennials (Quiros and Bauchan, 1988). Its primary center of diversity is located in the Caucasian region, and it is endemic to the Mediterranean region. The genus is present across the world in varying climates and soils. The history of this diversification is described (review by Michaud et al., 1988; Musial et al., 2005) and completed with new elements obtained through molecular data (Bena, Jubier, et al., 1998; Bena, Lejeune et al., 1998; Bena, Prosperi, et al.,1998; Muller et al., 2003). Most species have a chromosome number of eight; they are diploid or tetraploid, autogamous (annual species) or allogamous (perennial species). A small number of species are cultivated. Among the perennial species, the Medicago sativa complex, which was formed from intercrosses between the subspecies sativa, falcata, and glutinosa, contains cultivated alfalfa. Several annual species (M. truncatula, M. polymorpha, and others) are cultivated in rangelands in Mediterranean climates.
