Enhanced Indirect Somatic Embryogenesis from Shoot-Tip Explants of Date Palm by Gradual Reductions of 2,4-D Concentration.

Shoot-tip explants obtained from offshoots of adult date palms are an excellent source for callus induction and subsequent somatic embryogenesis. In this protocol, the shoot-tip explants are transferred sequentially to a series of media containing gradually reduced concentrations of plant growth hormones: (a) 10 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) and 3 mg/L 2-isopentenyl adenine (2iP), (b) 7 mg/L 2,4-D and 1 mg/L 2iP, (c) 5 mg/L 2,4-D and 1 mg/L 2iP, and (d) 3 mg/L 2,4-D and 1 mg/L 2iP. Embryogenic callus differentiates into somatic embryos upon transfer to MS medium containing 0.5 mg/L abscisic acid (ABA) and 0.1 mg/L naphthalene acetic acid (NAA). Well-matured somatic embryos germinate on a medium containing 0.1 mg/L NAA. Repeated, multiple, and secondary somatic embryos are induced to produce normal well-developed somatic embryos upon transfer to MS medium containing 0.1 mg/L NAA and 0.05 mg/L benzyladenine (BA). This protocol is potentially applicable for commercial micropropagation of date palm.