Regeneration of Acacia mangium through somatic embryogenesis

Somatic embryogenesis and whole plant regeneration were achieved in callus cultures derived from immature zygotic embryos of Acacia mangium. Embryogen ic callus was induced on MS medium containing combinations of TDZ (1-2 mg/l ), IAA (0.25-2 mg/l) and a mixture of amino acids. Globular embryos develop ed on embryogenic callus cultured on the induction medium. Nearly 42% of em bryogenic cultures with globular embryos produced torpedo- and cotyledonary -stage embryos by a two-step maturation phase. The first stage occurred on 1/2-strength MS basal medium containing 30 g/l sucrose and 5 mg/l GA(3) fol lowed by the second stage on 1/2-strength MS basal medium containing 50 g/l sucrose. Of the cotyledonary-stage somatic embryos, 11% germinated into se edlings that could be successfully transferred to pots. Light and scanning electron microscopy showed that the somatic embryos originated from single cells of the embryogenic callus. Further, a single cell layer could be dete cted beneath the developing somatic embryos that appeared to be a demarcati on layer isolating the somatic proembryonic structure from the rest of the maternal callus. A suspensor-like structure connected the globular embryos to the demarcation layer. This is the first successful report of plant rege neration through somatic embryogenesis for this economically important trop ical forest species.