Abstract: Experiments were conducted about tissue culture systems and cryopreservation on papaya ( Carica papaya L.) . The cluster buds were subcultured on the proliferation medium containing 0.5 mg/ L BA , 0.1 mg/ L
NAA and 1.0 mg/ L GA3. The procedure of cryopreservation was studied using the shoot tips as materials. In vitro, the shoot tips of papaya about 3-5 cm in length were precultured for 3 days at 25 ℃on MS medium supplemented
with 5 %DMSO. Shoot tips about 1.5-2.5 mm in length with one or two leaf primordiumwere loaded in a solution containing 60 % PVS2 for 40-50 min at room temperature. The shoot2tips were sufficiently dehydrated with a highly concentrated vitrification solution (PVS2) for 40 min at 0 ℃. After changing the solution with fresh PVS2 , the shoots were immersed into liquid nitrogen directly and conservated for 24 hour. After rapidly thawing in a water
bath at 40 ℃, the shoot tips were washed twice with 1.2 mol/ L sucrose solution and transferred on the same MS medium as the previous one. Survival rates of shoot tips was 53.7 % , and regrowth rate reached 52.6 %. Almost
all the shoot tips formed roots on hormone2free solidified MS medium and were successfully transferred to soil in pots. The plantlets could normally root and survive after transplantion.

Key words: Papaya (Carica papaya L.), Shoot-tips, Cryopreservation, Vitrification