Induction of direct somatic embryogenesis and genetic stability of somatic embryo-derived plants of broccoli

The influence of the developmental stage of zygotic embryos and the composition and pH of the Gamborg induction medium B5 on the initiation and development of somatic embryos was investigated. The optimal medium was B5 medium with a pH value of 5.0 and without plant growth regulator, at which the highest frequency of somatic embryogenesis (56.67%) and the highest average number of somatic embryos per explant (3.35) were achieved. Somatic embryos appeared directly on the hypocotyls of the explants, without the callus stage. On zygotic embryos in the early cotyledonary phase, three times higher regeneration was achieved compared to larger embryos in the cotyledonary phase. The induction of somatic embryogenesis did not occur during the growth of explants on the medium containinig 2,4-dichlorophenoxyacetic acid, nor on zygotic embryos in the late cotyledonary phase. Random amplified polymorphic DNA analysis showed the genetic stability of somatic embryo-derived plants, which makes this newly established protocol suitable for the regeneration and propagation of desirable broccoli genotypes.