Abscisic acid induced somatic embryogenesis in immature embryo explants of coconut (Cocos nucifera L.)

Somatic embryogenesis in coconut (Cocos nucifera L.)is generally induced by gradual reduction of auxin concentration in the culture medium and incorporation of cytokinins. Although plant regeneration through somatic embryogenesis is possible, the protocol is yet to be perfected. In this study, nodular callus was obtained from 7-9 months old immature zygotic embryos of coconut on a medium containing 24 µM 2,4-dichlorophenoxy acetic acid (2,4-D). As a novel approach, abscisic acid (ABA)at a concentration of 2.5-7.5 µM was incorporated into the culture medium for 3-7 weeks to induce somatic embryogenesis. Alternately, callus was subcultured at 5 weekly intervals on media containing gradually reducing concentrations of 2,4-D to induce somatic embryogenesis. Incorporation of ABA enhanced the production of somatic embryos. Application of 2.5-5 µM ABA for 5 weeks was found to be effective. A large number of somatic embryos developed on media containing ABA formed normal shoots and complete plants as compared to those produced in the media with low levels of 2,4-D.