Abstract: A procedure had been studied on cryopreservation of citrus shoot2tips in vitro by vitrification. Shoot-tips of citrus about 10 mm were precultured for 3 days in MT medium supplemented with 5 % DMSO. The excised shoot2tips , 2 - 2. 5 mm in length , were loaded with 60 % PVS2 for 20 - 30 min at room temperature , and were exposed to PVS2 at 0 ℃for 50 - 60 min. Followed by changing the solution with fresh PVS2 , the shoot2tips were immersed into LN directly , and kept for 24 h. After rapid thawing in a water bath at 40 ℃, the shoot2tips were washed with 1. 2 mol/ L sucrose solution for twice and transferred onto MT medium supplemented with BA 1. 0 mg/ L. The cultures were kept in dark for one week prior to exposure to the light . Survival rate of shoot2tips of Poncirus trifoliata was 100 % by TTC examination , and regeneration rate reached to 90 %. The plantlets rooted normally and survived after transplantion. No morphological difference between the regenerated
plantlets and the control was observed.

Key words: Citrus, Shoot-tips, Cryopreservation, Vitrification