Cryopreservation of in vitro sugar beet (Beta vulgaris L.) shoot tips by avitrification technique

Sugar beet shoot tips from cold-acclimated plants were successfully cryopre served using a vitrification technique. Dissected shoot tips were precultur ed for 1 day at 5 degreesC on solidified DGJ0 medium with 0.3 M sucrose. Af ter loading for 20 min with a mixture of 2 M glycerol and 0.4 M sucrose (20 degreesC), shoot tips were dehydrated with PVS2 (0 degreesC) for 20 min pr ior to immersion in liquid nitrogen. Both cold acclimation and loading enha nced the dehydration tolerance of shoot tips to PVS2. After thawing, shoot tips were deloaded for 15 min in liquid DGJO medium with 1.2 M sucrose (20 degreesC). The optimal exposure time to both loading solution and PVS? depe nded on the in vitro morphology of the clone. With tetraploid clones a high er sucrose concentration during cold acclimation and preculture further enh anced survival after cryopreservation. Survival rates ranged between 60% an d 100% depending on the clone. Since only 10-50% of the surviving shoot tip s developed into non-hyperhydric shoots, regrowth was optimized.