Cryopreservation of in vitro cultured shoot tips of strawberry

Shoot tips of in vitro cultured strawberry were successfully cryopreserved. Excised shoot tips were pre-cultured for 12 days on solid MS medium with 2% dimethylsulfoxide. They were firstly treated with a less toxic solution which contained 20% glycerol and OAM sucrose (pH 6.0) at room temperature for 20 min, and then pre-treated in PVS4 which contained 35% glycerol and 20% ethylene glycol in the liquid MS medium containing 0.6M sucrose (pH6.0) at 4 degrees C for 50 min before being immersed in liquid nitrogen. After 1 min warming at 40 degrees C, shoot tips were rinsed with liquid MS medium containing 1.2M sucrose for 30 min, and transferred onto MS medium supplemented with BA 0.4mg/L, NAA 0.05mg/L and GA 0.15 mg/L. The survival rate reached 82.1%, and regrowth of shoot tips was 61.3%. This is the first report of the cryopreservation of strawberry using a one-step vitrification procedure.