CRYOPRESERVATION BY ENCAPSULATION-DEHYDRATION OF IN VITRO GROWN SHOOT BUDS OF ROSA 'NEW DAWN'

In the present study, preliminary experiments toward developing a protocol of cryopreservation of shoot meristems of park rose (Rosa) ‘New Dawn’ in liquid nitrogen by the encapsulation-dehydration were conducted. Shoot apical and axillary meristems of about 1-2 mm were collected from plants propagated in vitro on Quoirin et al. (1977) medium, with 5 µM BA, 0.3 µM GA₃, 0.5 µM NAA and 0.06 M sucrose. Some explants for cryopreservation were pretreatment on the medium containing a higher sucrose (0.25 M) or 2.5 g dm^-3 activated charcoal for 2 weeks. After encapsulation the plant material was precultured by a quick method (shoot tips in beads were placed in liquid medium containing 0.75 M sucrose for 18 h) or by a gradual method (beads were transferred to solutions with increasing sucrose concentrations from 0.3 to 1 M daily for consecutive 7 days), then desiccated and transferred to liquid nitrogen (LN₂). The survival of plant tissue after freezing in LN₂ depended on the plant material: apical meristems regenerated some shoots and mostly callus but axillary meristems regenerated only callus. When rose shoots were cultivated on medium with activated charcoal before encapsulation, 20% of frozen explants developed shoots. Removing the shoot tips from the alginate beads after rewarming did not influence regeneration of the cryopreserved explants.