EFFECT OF PRECULTURE, PVS2 ANDVITAMIN C ON SURVIVAL OF RECALCITRANTNephelium ramboutan­akeSHOOT TIPSAFTER CRYOPRESERVATION BYVITRIFICATION

This paper reports the cryopreservation ofNepheliumramboutan­akeshoot tips derived fromin vitroshoot multiplication andin vitroseedgermination using vitrification. Preculture with either0.5 M sucrose for2daysoracombination of 0.3 M sucroseand0.5 M glycerolfor 3 daysenhanceddehydrationtolerance andresulted in thehighest survival of shoot tips; however,none of the shoottips withstoodliquid nitrogen(LN)exposure.The use ofalower temperature (0°C)duringexposureto plant vitrification solution (PVS2)led to higher survival of shoot tips, compared toexposure at25°C. The survivalpercentageofshoot tips exposed to PVS2forup to 20 min at 0°Cwas83.3%. It was only53.3% when shoot tips were exposed to PVS2 at 25°Cfor5 min.The importance of vitaminC forreducingoxidative stressinshoots tips was demonstrated.The addition of0.28 mM vitamin Cduringcritical steps of the vitrification process resulted in a high survival (96.67%)without LN exposure,compared to 73.3% for shoot tipsnottreated withvitamin C. Moreover,3.3%shoot tips withstoodLN exposurewhen vitamin C was added during the loading step.Thisresult suggests that cryopreservation is possible for this tropical, recalcitrant seededtree species.