A new approach to direct somatic embryogenesis in Medicago

A highly efficient system for direct somatic embryogenesis is described. Leaf sections originating from young trifoliate leaves of Medicago falcata line 47/1-5 and Medicago sativa line No2/9R, directly produced embryos after cultivation in liquid B5IV induction medium. In comparison with indirect somatic embryogenesis the system omits the callus stage and thus allows shortening of the process of somatic embryogenesis in alfalfa by 35-40 days. It permits the avoidance of secondary changes occurring during the process of dedifferentiation. A modified B5/3H medium containing Polyethylene Glycol 6000 promoted embryo development from globular up to torpedo stage. It was clearly shown that 2.5% Polyethylene Glycol stimulated this process for both H. falcata 47/1-5 and M. sativa No 2/9R. Maturation of torpedo stage embryos was carried out on solidified or liquid abscisic acidcontaining medium. A 30μM abscisic acid concentration was optimal in allowing one embryo to yield one plant. Somatic embryo conversion to plants and plant regeneration was performed on Murashige and Skoog medium. Regenerated plants showed a normal morphology.