Factors Affecting Somatic Embryogenesis Induction and Conversion in 'Paradise Tree' (Melia azedarach L.)

摘要

Factors affecting somatic embryogenesis induction and conversion in paradise tree (Melia azedarach) were evaluated. Somatic embryogenesis was influenced by plant growth regulators, explant stage, carbohydrate source and concentration, gelling agents,light, and induction times. MS medium with 4.54 mu M thidiazuron (TDZ) was optimal for the induction of embryogenic tissue. Zygotic embryos that were 1-1.5 mm long (torpedo and early cotyledonal stage) had a greater embryogenic response than smaller or larger embryos and better conversion of somatic embryos into plants. In general, embryos that formed in medium containing 1% or 5% carbohydrate were hyperhydrics or fused, respectively, whereas those that formed in medium with a carbohydrate concentrationof 3% had better morphology. Raffinose at 3% yielded satisfactory somatic embryo induction with good morphology and the best values of conversion into plants. Induction and conversion of somatic embryos were superior on medium solidified with agar A-1296. The ex-plants maintained under 160 umol m~(-1) s~(-1) or 1 week in darkness and later 160 umol m~(-2) s~(-1) produced a significantly higher embryogenic index. Only 4 days of treatment on induction medium, with either raffinose or sucrose at 3% as a carbohydrate source, were required to induce somatic embryogenesis, but longer exposure, until 18 days, increased the yield and improved the morphology of somatic embryos.