Enhanced Coconut Somatic Embryogenesis of Unfertilized Ovary Derived Callus through Improved Media Composition

Abstract

Coconut is an economically demanding plantation crop in Sri Lanka, having an out-breeding nature with no vegetative propagation methods. Propagation by seeds generates heterogenous population and it is not sufficient to fulfill the increasing demand for coconut plantlets. Therefore, in vitro propagation is the ultimate approach of producing clones of coconut from the mother palms of interest. Coconut in vitro propagation is achieved through somatic embryogenesis and improvements of this process will easily cater the demand for plantlets. Hence, the main objective of the study was to enhance somatic embryogenic pathway of coconut using two different auxins (2,4-Dichlorophenoxyacetic acid [2,4-D] and 3,6-Dichloro-2-methoxybenzoic acid [Dicamba]) at the concentration of 300 μM. These auxins were tested alone and in combination with calcium ionophore (A23187) and 22(S),23(S)-homobrassinolide. Translucent structures or the ear-like structures obtained from culturing of unfertilized ovaries were used for the treatments. After six weeks of the culture establishment number of embryogenic structures per one translucent structure were counted. Each treatment produced embryogenic structures but a significantly greater number of embryogenic structures were developed with 2,4-D containing media than dicamba. The results revealed the potential of using 300 μM 2,4-D with calcium ionophore (A23187) and 22(S), 23(S)-homobrassinolide to improve the somatic embryogenic pathway of unfertilized ovary derived callus of coconut.