Y. Samosir

Dehydration improves cryopreservation of coconut (Cocos nucifera L.)

Cryopreservation of coconut can be used as a strategy to back up the establishment of living collections which are expensive to maintain and are under constant threat from biotic and abiotic factors. Unfortunately, cryopreservation protocols still need to be developed that are capable of producing a sizeable number of field-grown plants. Therefore, we report on the development of an improved cryopreservation protocol which can be used on a wide range of coconut cultivars. The cryopreservation of zygotic embryos and their recovery to soil-growing plants was achieved through the application of four optimised steps viz.: (i) rapid dehydration; (ii) rapid cooling; (iii) rapid warming and recovery in vitro and (iv) acclimatization and soil-supported growth. The thermal properties of water within the embryos were monitored using differential scanning calorimetry (DSC) in order to ensure that the freezable component was kept to a minimum. The feasibility of the protocol was assessed using the Malayan Yellow Dwarf (MYD) cultivar in Australia and then tested on a range of cultivars which were freshly harvested and studied in Indonesia. The most efficient protocol was one based on an 8-h rapid dehydration step followed by rapid cooling step. Best recovery percentages were obtained when a rapid warming step and an optimised in vitro culture step were used. Following this protocol, 20% (when cryopreserved 12 days after harvesting) and 40% (when cryopreserved at the time of harvest) of all MYD embryos cryopreserved could be returned to normal seedlings growing in soil. DSC showed that this protocol induced a drop in embryo fresh weight to 19% and significantly reduced the amount of water remaining that could produce ice crystals (0.1%). Of the 20 cultivars tested, 16 were found to produce between 10% and 40% normal seedlings while four cultivars generated between 0% and 10% normal seedlings after cryopreservation. This new protocol is applicable to a wide range of coconut cultivars and is useful for the routine cryopreservation of coconut genetic resources.

Cryopreservation of coconut ( Cocos nucifera L.) : the influence of embryo maturity upon rate of recovery and fidelity of seedlings

The application of biotechnology in plant breeding requires efficient in vitro regeneration procedures. This study describes in vitro regeneration of strawberry via direct organogenesis for three cultivars: Festival, Sweet Sharly, and Florida. The in vitro juvenile leaves were used as explants. Explants were collected after culturing the meristem tip and leaving such to multiply on a propagation medium composed of MS supplemented with BA at a concentration of 0.5 mg/l and Kin at a concentration of 1 mg/l. To select the suitable organogenesis, the explants of the three cultivars were cultured on MS medium supplemented with different concentrations of TDZ (1, 2, 3, and 4 mg/l) and incubated at a temperature of 22±2°C. Direct shoot regeneration occurred in all the tested cultivars from juvenile leaves 10 d postcultivation. The medium containing 2 mg/l TDZ revealed the best regeneration efficiency with the three cultivars (72% for cultivar Festival and 73% for both cultivars Sweet Sharly and Florida). After 4 wk, the shoots produced were cultured in MS medium with different concentrations of BA and Kin for elongation. The medium containing 1.5 mg/l BA and 0.5 mg/ l Kin was the best medium for the all the tested cultivars. Elongated shoots were rooted by culturing and incubating shoots on MS medium containing 1.5 mg/l NAA for 4 wk.

Control of environmental conditions and the use of polyamines can optimise the conditions for the initiation and proliferation of coconut somatic embryos

Coconut (Cocos nucifera L.) is one of the most important oil crops in the tropics. Unfortunately, conventional breeding is difficult to undertake due to the long juvenile phase of the tree and the low rate of seed production. Therefore, it has been suggested that traditional coconut breeding could be supplemented with in vitro tissue culture techniques, such as somatic embryogenesis. This procedure could speed up the rate of elite germplasm production and provide a method for rapid trait manipulation via genetic engineering. Although several decades of research on coconut somatic embryogenesis have been undertaken no reliable protocol has been developed (Branton and Blake, 1983). The major problems seem to be the heterogeneous response of the explanted tissues, their premature necrosis and death and the inability of the few somatic embryos that are produced to mature and form plants. The heterogeneous response and premature necrosis of the explanted tissue, are thought to be related to production of phenolic substances, which then bind up key amino acids and proteins (Chalker-Scott and Fuchigami, 1989) thus preventing critical enzymatic processes from taking place. In coconut, as with many other species the application of activated charcoal (AC) has been attempted as a way of overcoming these premature necrosis problems, but with limited success.

The use of osmotically active agents and abscisic acid can optimise the maturation of coconut somatic embryos

Coconut (Cocos nucifera L.) is one of the most important oil crops in the tropics where it is known as “the tree of life” (Persley, 1992). Oil extracted from its dried endosperm (copra) is the main reason for production and a major source of short-chain (8 to 14 carbon atoms) fatty acids (Berger and Ong, 1985). The main copra producing countries are the Philippines and Indonesia.