Developing a cryopreservation protocol for the conservation of coconut palm (<i>Cocos nucifera</i> L.) using a novel type of explant, meristematic clumps

BACKGROUND: The coconut palm is a major agricultural crop. The preservation of its genetic diversity is important to allow farmers to adapt to novel circumstances such as climate change, new diseases or consumer demand. However, the tools and methods available to conserve clonal material for the long-term are currently limited. OBJECTIVE: To determine whether a new type of explant, meristematic clumps, resulting from a novel shoot micropropagation method, could be used to cryopreserve coconut clonal material using droplet-vitrification. MATERIALS AND METHODS: Whilst applying the droplet-vitrification protocol, different PVS2 treatment times, explant sizes, preculture durations and vitrification solution compositions were applied. After cryopreservation, the explants were rewarmed and checked for survival, proliferation and regeneration. RESULTS : Whilst toxic effects of the vitrification solutions were observed, increasing the PVS2 treatment duration to 120 min and even 240 min resulted in around 50% post-cryopreservation survival. However, the post-cryopreservation proliferation percentage was lower, viz. 22% or less. This drop may be partly explained by the blackening of explants that also occurred during normal proliferation. CONCLUSION: A cryopreservation protocol for coconut using this novel type of explant was developed and proved to be promising.