An improved protocol for somatic embryogenesis in coconut (Cocos nucifera L.)

An improved protocol for somatic embryogenesis in coconut (Cocos nucifera L.) has been established. Immature zygotic embryo explants were found to be more likely to undergo somatic embryogenesis than mature ones. However, longitudinally slicing of the mature zygotic embryo did improve their ability to undergo somatic embryogenesis. The slices derived from the mid-embryo region were the most responsive, with outer sections not producing any somatic embryos. To induce somatic embryogenesis on sliced mature explants 2,4-D (125 mu M) and activated charcoal (2.5 g l(-1)) were required. Incubation of cultures under illuminated conditions inhibited the production of somatic embryos. However, maturation of somatic embryos was light insensitive while plantlet regeneration required illumination. Plantlets were successfully produced, but elongation of shoots was inhibited by the production of a large root system. Removal of these early roots and the re-establishment at a later stage by application of NAA (10 mu M) allowed for normal seedling growth to occur. Plantlets were acclimatised (with a 30% survival rate) and grew normally in a glasshouse.