In this study, we compare two rapid cryopreservation (-196 °C) procedures, droplet-vitrification and encapsulation-dehydration for rose (Rosa × hybrida L., cultivars 'Ioana', 'Mariana', 'Vulcan'). Significant factors for cryopreservation, such as sucrose concentration during osmoprotection, treatment duration with plant vitrification solution 2 (PVS2) in droplet-vitrification, duration of air desiccation and moisture content of alginate beads in encapsulation-dehydration, were investigated. In addition, the morphogenetic response to in vitro culture and to liquid nitrogen storage and the content in photosynthetic pigments have been assessed. The in vitro cultures were initiated from plant material originating from field collection. The highest regeneration frequencies were obtained for cv. 'Vulcan' in both of the cryopreservation procedures tested, 72% in droplet-vitrification and 65% following encapsulation-dehydration. The morphogenetic response (multiplication index and height of shoots) to liquid nitrogen storage was direct multiple shoot formation per initial shoot tip for all genotypes. The content in chlorophyll a and b was statistically comparable in plant material resulting from cryopreserved and non-cryopreserved shoot tips in all cultivars. The findings expand the information on Rosa's response to in vitro culture conditions and cryopreservation, providing protocols with a high regeneration capacity for the storage of genotypes with high ornamental value.
Keywords: droplet-vitrification; encapsulation-dehydration; genetic resources; long-term storage.