| || || Sant, Rajnesh R. Prasad.|
| || || Cryopreservation of taro (Colocasia Esculenta var. Esculenta) |
Author:Sant, Rajnesh R. Prasad.
Institution: University of the South Pacific.
Subject: Taro -- Germplasm resources -- Cryopreservation
Call No.: pac QK 725 .S25 2001
Copyright:Over 80% of this thesis may be copied without the authors written permission
Abstract: From this study it was discovered that the hormone-free clonal propagation system developed by Thinh (1997) for Colocasia esculenta var. antiquorum, based on enhanced axillary branching (multiple shoot formation) through liquid TDZ medium shake culture and subsequent carry over effect on hormone-free medium, did not work with the tropical taro variety, Tausala ni Samoa, of Colocasia esculenta var. esculenta type. After two four-week cycles on liquid TDZ shake medium cultures, no enhancement in proliferation rates was noted and no carry over effect was observed when these plants were transferred to hormone-free media. The vitrification method of cryopreservation was experimented with cultivars of the tropical taro (Colocasia esculenta var. esculenta) and the technique was shown to have potential for the cryopreservation of taro from Pacific Island countries. Out of the eight taro cultivars experimented with, three, namely E399, CPUK and TNS, were successfully cryopreserved with average recovery rates of 20, 29 and 29%, respectively. The optimum vitrification protocol for the cultivars E399 and CPUK was; using shoot-tip donor plants cultured on solid MS in large jars for three months as sources of shoot-tips, which consisted of the apical dome surrounded by two leaf primodia; preculturing these shoot- tips overnight (16hr) on 0.3 M sucrose medium; loading with liquid MS supplemented with 2 M glyceroi + 0.4 M sucrose for 20 min at 25°C, dehydrating with PVS2 for 12 min at 25°C followed by rapid immersion in LN. Thawing was done by shaking the shoot-tips rapidly for 90 sec in waterbath at 40°C, followed by rehydration in liquid MS medium supplemented with 1.2 M sucrose for 15 min. The shoot-tips were then plated on a layer of filter paper on MS medium supplemented with 0.3 M sucrose and left overnight in the dark. Next day, they were transferred onto MS medium supplemented with 0.1 M sucrose and maintained in the dark for three days, then transferred to dim light (10 u.molm"V) for one week before exposure to normal culture conditions. Piantlets were produced after about two months. For cultivar TNS, the optimum vitrification protocol was preconditioning explants on solid MS supplemented with 90 g/1 sucrose for seven weeks prior to dissecting and cryopreserving the shoot-tips without any preculture, The vitrification procedure was same as described above. During this study, it was found that the vitrification protocol has to be optimized for each individual taro cultivar.