Induction of Direct Somatic Embryogenesis from Immature Embryos of Brassica oleracea var. Sabauda L.

Abstract

An efficient plant propagation system through somatic embryogenesis by using immature zygotic embryos was established in Savoy cabbage (Brassica oleracea var. sabauda L.). The effects of zygotic embryo age, presence of 1 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) (B5-D) in the culture medium, and the pH (5.0 and 5.8) of the B5 plant growth regulator (PGR)-free (B5-0) induction media were investigated. It appeared that the developmental stage of the immature zygotic embryos used as explants was the most important factor for somatic embryogenesis. Highest frequency of somatic embryogenesis (86.67%) was achieved directly on zygotic embryos at cotyledonary stage (1.8 mm long) of development that cultured on B5-0 medium. Optimal pH of the medium was 5.0. Mean number of primary somatic embryos per explant on B5-0 pH 5.0 medium was 7.2. The inclusion of 2,4-D into the induction medium significantly reduced both frequency of somatic embryogenesis (to 53.34 %) and mean number of embryos per explant (to 2.62) in cotyledonary zygotic embryos. After transferring to PGR-free Murashige and Skoog (MS-0) medium 69.69% of the primary somatic embryos of the Savoy cabbage produced secondary somatic embryos (SSEs) Effective recurrent somatic embryogenesis may be an appropriate practical solution for clonal propagation and genetic modifications of Savoy cabbage.