CRYOPRESERVATION OF CITRUS APICES USING THE ENCAPSULATION-DEHYDRATIONTECHNIQUE

Cryopreservation of apices sampled on in vitro plantlets of Poncirus t rifoliata (L.) Raf. was achieved using the encapsulation-dehydration t echnique. The highest survival rates after cryopreservation (up to 50 %) were obtained when encapsulated apices were pregrown for 3 d either directly in liquid medium containing 0.5M sucrose or in media with pr ogressively increasing sucrose concentration from 0.3 to 0.75M, desicc ated to 20-25% moisture content and frozen slowly (0.5 degrees C.min(- 1)) from +20 degrees C to -40 degrees C before immersion in liquid nit rogen. Recovery of whole plantlets from cryopreserved apices took plac e directly, without transitory callus formation.