A New Technique for Coconut (Cocos nucifera) Germplasm Collection from Remote Sites: Culturability of Embryos Following Low-temperature Incubation

Abstract

A new technique for coconut (Cocos nucifera L.) germplasm collection was evaluated in the laboratory and tested in the field in Indonesia. The technique involved the non-sterile isolation of embryos, and incubation in sterile ascorbic acid solution (1 mg L –1 ) at 5 1˚C in the dark. During this incubation period the embryos could be transported and/or stored for a period of up to 4 days without embryo viability loss. Following this period the embryos were surface sterilised with sodium hypochlorite (1.5% w/v) for 20 min, washed with sterile water and cultured in a liquid Y3 basal nutrient medium supplemented with Morel and Wetmore vitamins, sucrose (175 mM) and activated charcoal (2.5 g L –1 ). After two weeks the embryos were subcultured onto a solid medium of similar constitution to encourage germination. Germinated embryos grew and produced healthy plants with normal morphology. Despite mild chilling injury as indicated by elevated ethylene production and solute leakage, the transported embryos retained viability with normal morphology. Using the low-temperature incubation treatment, the microorganism density in the ascorbic acid solution was kept low while that around other embryos kept at higher temperatures (25˚C) increased. Even though embryos were exposed to a low-temperature treatment for up to 4 days they were able to germinate (95% viable) and grow in an identical fashion to freshly cultured embryos.