INDUCTION OF SOMATIC EMBRYOS IN PLUMULE EXPLANTS OF COCONUT BY ABSCISIC ACID AND POLYETHYLENE GLYCOL

Abstract

The increasing demand for coconut palms (Cocos nucifera L.) requires massive multiplication of improved or selected plants. This
could be achieved through micropropagation. A reproducible regeneration protocol by somatic embryogenesis from plumule explants has already been reported, although its efficiency is still low. Therefore the objective of the present research was to evaluate the effect of different concentrations of abscisic acid (ABA) (0, 22.5, 45 and 90 µM) and polyethylene glycol (PEG) (0, 15, 30, 60 g L^-1) on the formation of somatic embryos and their conversion into plants using plumule explants of coconut palm. The response was evaluated at 30, 60, 90, 150 and 210 days after the addition of ABA or PEG to the medium II Y3. The best treatment was 90 µM ABA + 15 g L^-1 of PEG with the formation of 10.6 somatic embryos per embryogenic callus at 150 days of culture and the formation of three well developed plantlets per embryogenic callus after 210 days of culture. Instead, only 6.2 somatic embryos and 0.7 plantlets were obtained from untreated embryogenic calli. Plantlets obtained from 90 µM of ABA + 15 g L^-1 PEG and from controls were acclimated in a greenhouse, having a 90 % plant survival after one year. This treatment increased both the yield of somatic embryos (by 71 %) and the plantlet formation (4 times), thus enhancing the system overall efficiency which eventually may have a practical application. This is the first report on the use of ABA and PEG when coconut plumules are utilized as explants.