Effect of Abscisic Acid on Survival and Recovery of Cryopreserved Plumule Explants of Coconut (Cocos nucifera)

Cryopreservation has great potential for long-term storage of coconut genetic resources. The recent development of the encapsulation-dehydration cryogenic technique dramatically facilitated progress with cryopreservation. The present study tested the effect of abscisic acid in the encapsulationdehydration method for cryopreservation of coconut plumules. Plumules were excised from mature zygotic embryos of Coconut var. Sri Lanka Tall and encapsulated in calcium alginate. The alginate beads were used to test effect of different cryoprotection pretreatments (mixtures of 0.75 M sucrose and abscisic acid (ABA) at concentrations of 0, 10, 20 and 40 μM), and exposure to silica gel for 16 hours for further dehydration, prior to freezing in liquid nitrogen. Effect of the treatments without freezing was also tested. The water loss from alginate beads following sucrose incubation and dehydration was monitored, and the survival and growth of plumules assessed at different stages. Addition of ABA to the sucrose pretreatment medium increased the survival rate of unfrozen plumules from 60% to over 80%. Pretreatment with 40 μM ABA gave the highest survival rate (84%) of frozen plumules. The recovery rate of plumules (frozen and unfrozen) pretreated without ABA was very low (6-8%). The addition of ABA increased the recovery rate significantly; frozen plumules that had been treated with 40 μM ABA recorded a 39% recovery rate. The improved recovery could be ascribed to increased water loss (69%) in plumules treated with 40 μM ABA. Key words: Coconut, plumule, cryopreservation, abscisic acid doi: 10.4038/cocos.v18i0.989 COCOS (2007), 1