Embryo maturity plays an important role for the successful cryopreservation of coconut (Cocos nucifera)

Genetic diversity of coconut (Cocos nucifera L.) is being lost due to a combination of pest and disease attack, urban encroachment, natural disasters, as well as introgression with exotic genetic types. Consequently, there is a need to undertake germplasm conservation before further loss occurs. Since coconut has a large, recalcitrant seed (sensitive to desiccation), it cannot be stored in traditional ways in a seed bank. Cryopreservation of zygotic embryos is now seen as an important storage approach although published techniques are still not reliable. Given the importance of embryo maturity to the success of cryopreservation in other species, the effect of coconut embryo maturity on cryopreservation success was investigated using four cultivars ('Nias Yellow Dwarf', 'Tebing Tinggi Dwarf', 'Takome Tall', and 'Bali Tall'). After cryopreservation, using a new four-step protocol (rapid desiccation, rapid freezing, rapid thawing, and recovery and acclimatization for 4 mo in the glasshouse), we found that the embryos isolated from an 11-mo-old fruit gave the highest number of normal seedlings (similar to 28%) when compared to counterparts excised from younger fruits. In addition, the results showed that fruit could be stored for up to 3 wk prior to embryo isolation before their performance in cryopreservation was compromised.