Direct somatic embryogenesis, plant regeneration and in vitro flowering inrapid-cycling Brassica napus

A simple method to induce somatic embryogenesis from seeds of rapid-cycling Brassica napus is described. Seedlings cultured on Murashige and Skoog (MS ) basal medium produced somatic embryos directly on hypocotyls and cotyledo ns after 2 to 3 subcultures onto the same medium. A low pH of the medium (3 .5-5) was more conducive to somatic embryogenesis than a higher pH (6 and 7 ). Embryogenic potential of the seeds was inversely correlated to seed age: about 41-68% of immature seeds between the ages of 14 and 28 days after po llination (DAP) formed somatic embryos compared to 0-11% of the seeds obtai ned 29-37 DAP. About 54% of the somatic embryos produced secondary embryos after subculturing onto the same medium. The embryogenic potential of the c ultures has been maintained on MS basal medium for 2 years (12 generations) without diminution. Up to 75% of the secondary embryos developed into plan tlets on MS medium enriched with 10(-6) M zeatin, and 40% of these produced flowers when transferred to an optimised flower-induction medium. Viable s eeds were produced in self-pollinated in vitro flowers.