A combined pathway of organogenesis and somatic embryogenesis for an efficient large-scale propagation in date palm (Phoenix dactylifera L.) cv. Mejhoul.

Abstract

An efficient regeneration system via a combined pathway of organogenesis and somatic embryogenesis was developed for date palm (Phoenix dactylifera L.) cv. Mejhoul. Adventitious buds were obtained from shoot-tip explants with a frequency of 53.3% after 9months of culture: 6months on half-strength Murashige and Skoog (MS/2) medium containing 14.2µM indole-3-acetic acid (IAA), 13.4µM 1-naphthaleneacetic acid (NAA) and 0.5µM 6-(dimethylallylamino) purine (2iP), and 3months on MS/2 medium supplemented with 1.1µM IAA, 1.1µM NAA, 0.5µM 2iP, 2.2µM 6-benzyladenine (BA) and 0.4µM kinetin. Adventitious bud segments were used as explants to induce somatic embryogenesis, and the effects of different concentrations (22.5, 45, 90, 225 or 450µM) of 3,6-dichloro-o-anisic acid (dicamba) and 4-amino-3,5,6-trichloropicolinic acid (picloram) were evaluated. The optimal medium for somatic embryogenesis induction was MS medium supplemented with 45µM picloram and 5µM 2iP, in which the somatic embryogenesis rate was 70%. For somatic embryo maturation, the effects of sorbitol, mannitol, polyethylene glycol (PEG) and abscisic acid (ABA) were tested. The highest maturation rate (88.6 mature somatic embryos per 100mg fresh weight callus) was observed on liquid MS medium supplemented with 20gL-1 PEG. Subsequent somatic embryo germination was achieved with up to 52.0% in MS medium containing 2.5µM NAA and 2.5µM BA. The regenerated plantlets were transferred to the glasshouse where 76.0% of them survived.