In vitro conservation of Passiflora suberosa L.: slow growth and cryopreservation.

Passiflora suberosa is a tropical species used as an ornamental, in popular medicine and in improvement programs. The goal of this study was the development of in vitro conservation strategies for this species, including medium-term storage through slow growth, and long-term storage through cryopreservation using vitrification-based techniques. Plants were maintained under slow growth conditions on half strength MSM or one quarter strength MSM medium for 12 months without decrease in regrowth ability. The efficiency of vitrification and encapsulation-vitrification protocols was compared in order to determine the optimal conditions for successful cryopreservation. Several parameters were evaluated, including pregrowth on medium with high sucrose concentrations, type of vitrification solution (PVS2 and PVS3), exposure time to vitrification solutions, and recovery conditions. The highest recovery was obtained with the encapsulation-vitrification protocol after a pretreatment with 0.3 M sucrose and post-cryopreservation incubation in the dark for 30 days on MSM medium supplemented with 0.44 micromole BA.