Short communicationDirect-shoot organogenesis as an alternative protocol for in vitro regeneration of oil palm (Elaeis guineensis Jacq.)

- Cytokinin types, a degree of concentration and hormonal incubation period play the key roles on shoot induction of oil palm.
- Direct-shoot organogenesis from seedling-derived shoot of oil palm on MS medium supplemented with 9.8 μM 2-iP was successfully established.
- Simple, rapid and reproducible protocol in direct-shoot organogenesis of oil palm, prior to transfer into soil was investigated with true-to-type and clonal fidelity.

In the present study, in vitro culture via direct-shoot organogenesis was firstly established as an optional route for clonal propagation in oil palm (Elaeis guineensis Jacq.). The shoot explant excised from zygotic embryo-derived seedling was cultured on half-strength MS (½MS) medium supplemented with two cytokinins, N6-benzyladenine (BA; 8.9, 17.8, 35.5 and 71.0 μM) or 6-(γ,γ-dimethylallylamino) purine (2-iP; 9.8, 19.7, 39.4 and 78.7 μM). The highest percentage of shoot induction (54.2%) with 5 shoots per explant was obtained when shoot explants were cultured on ½MS medium supplemented with 9.8 μM 2-iP. The frequency of direct-shoot organogenesis expressed in the term of percentage of shoot induction was significantly influenced by the duration of incubation period on shoot induction medium. The optimal incubation period of shoot explants on the induction medium (½MS + 9.8 μM 2-iP) was found to be 4 weeks, which improved the frequency of shoot induction up to 2.6-fold, comparing to those obtained from incubation period of 8 weeks. Histological examination of induced shoots confirmed that newly developed shoot was directly regenerated via direct-shoot organogenesis. Oil palm plants derived from a defined regeneration regime in this study were successfully established in greenhouse. The study established the incubation of 4th week-developmental stage of seedlings as initial explant on shoot induction medium (½MS medium containing 9.8 μM 2-iP) with incubation period of 4 weeks as the successful protocol for the direct-shoot organogenesis of oil palm.