Alfalfa (Medicago sativa L.) is one of the most important forage crops in the world. It has been originated from the Caucasus region (Michaud et al., 1988) . The species presents purple flowers, a tap root, an erect growth habit, coiled pods and no winter dormancy. This plant improves the yield and quality of the following crops by atmospheric nitrogen fixation (Bruulsema and Christie, 1987) . Furthermore, it reduces diseases