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Transporting Coconut Zygotic Embryoes For Cryopreservation Of Plumules By Encapsulation/Dehydration

Systematic collection and conservation of coconut germplasm is essential in order to arrest the genetic erosion and to obtain new material for genetic improvement and to support innovative and new research. The recalcitrant storage behaviour and large size of the coconut seed make it impossible to use as a germplasm storage material. Cryopreservation that is done by storing cells or tissues at ultra-low temperature in liquid nitrogen (-196 °C) is the only viable option available currently for the long-term conservation of germplasm of plant species with recalcitrant seeds such as coconut. Due to storage at ultra-low temperature, cell division and metabolic activities are arrested and thus, plant material can be stored for unlimited period of time without causing any change in viability, vigour and genetic makeup. Furthermore, cryopreserved material requires very limited space, is protected from exogenous contamination and needs very limited maintenance. Thus development of methodologies for cryopreservation of coconut germplasm to complement the current conservation efforts is vital.


So far several cryopreservation techniques using different coconut explants have been tested for coconut cryopreservation. The first one developed, based on slow cooling using mature zygotic embryos had limited usefulness in coconut. Coconut plumule, which is known to be free of viral diseases, appears to be an interesting starting material for cryopreservation and it has been attempted using encapsulation/dehydration method. The coconut embryo is now being routinely used in germplasm collection and exchange activities with sufficient germination rates. Coconut embryo is also an ideal material for the international exchange of coconut germplasm for the establishment of multi-site international cryo genebanks in future. Method of transportation or storage conditions affects the embryo quality which in turn plays a crucial role in success of cryopreservation. A study was conducted to determine the effect of different coconut embryo transport or storage methods as solid endosperm plugs under cold temperature, embryos cultured in solidified agar medium (SAM) or in KCl solution under room temperature on cryopreservation of plumules using encapsulation/dehydration method.



The results revealed that plumules which were non-dehydrated and non-cryopreserved always showed high recovery rates (> 95%) irrespective of the transport/store condition and the sucrose concentration. There was a significant interaction effect of transport condition, sucrose concentration and dehydration. Although two sugar concentrations, 0.75 M and 1.0M, were able to protect a proportion of plumules from dehydration damage, only the embryos which were transported in SAM and pretreated with 1.0 M sucrose showed significantly high recovery (56%) after cryo storage. The recovery could be further increased up to 65% when osmotic dehydration was carried out using 1.0 M sucrose supplemented with 20 µM ABA.

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