Cryopreservation of encapsulated plumules of coconut: effect of transport/store conditions

* Author for correspondence: Research Institute, Lunuwila, Sri Lanka. Email: [email protected] Abstract. Attempts were made to identify the most suitable method to transport/store mature zygotic embryos of coconut (for excision of plumules later on) for cryopreservation work. Three different conditions, embryos transported/stored in albumen (solid endosperm) cores, solidified agar [0.45 %( w/v) agar] and KCl solution (16.2 g/L) were tested. Encapsulation/dehydration method was employed for cryopreservation. In this method, the plumules were excised from mature zygotic embryos (transported/stored under the 3 conditions indicated above) and encapsulated in sodium alginate. The beads were then pretreated with 0.75 M or 1.0 M sucrose. Prior to freezing in liquid nitrogen (LN), the plumules were subjected to further desiccation (D) by exposure to silica gel for 16 h. The condition used to transport/store embryos prior to excision of plumules has a significant effect on recovery of dehydrated but unfrozen plumules (+D/-LN) that were pretreated with 0.75 M sucrose. The plumules excised from embryos stored in KCl and solidified agar showed a significantly higher rate of recovery when compared to albumen cores. However, in frozen plumules (+D/+LN), there was no significant difference in recovery under 3 conditions tested. In frozen plumules (+D/+LN) pretreated with 1.0 M sucrose, the rate of recovery (40%) was significantly higher in the ones excised from embryos stored in solidified agar when compared to the other two conditions. However, this difference is not reflected in unfrozen plumules (+D/-LN).