Cryopreservation of in vitro-grown shoot tips of grapevine by encapsulation-dehydration

In vitro-grown shoot tips of the LN33 hybrid (Vitis L.) and cv. Superior (V itis vinifera L.) were successfully cryopreserved by encapsulation-dehydrat ion. Encapsulated shoot tips were precultured stepwise on half-strength MS medium supplemented with increasing sucrose concentrations of 0.25, 0.5, 0. 75 and 1.0 M for 4 days, with one day for each step. Following preculture, encapsulated shoot tips were dehydrated prior to direct immersion in liquid nitrogen for 1 h. After thawing, cryopreserved shoot tips were post-cultur ed on a post-culture medium for survival. An optimal survival of cryopreser ved shoot tips was achieved when encapsulated shoot tips were dehydrated to 15.6 and 17.6% water content for the LN33 hybrid and cv. Superior, respect ively. Comparison between the effects of dehydration with silica gel and by air drying on cryopreserved shoot tips, showed that survival was dependent on water content, not on dehydration method. The thawing method markedly a ffected survival of cryopreserved shoot tips, and thawing at 40 degreesC fo r 3 min was found best. No callus formation and fastest shoot elongation we re obtained when cryopreserved shoot tips were post-cultured on the post-cu lture medium composed of half-strength MS supplemented with 1 mg l(-1) BA a nd 0.1 mg l(-1) NAA. With these optimized parameters, 60 and 40% survival o f cryopreserved shoot tips were obtained for the LN33 hybrid and cv. Superi or, respectively.