Cryopreservation of redwood (Sequoia sempervirens) in vitro buds using vitrification-based techniques

In this study, the efficiency of three vitrification-based cryopreservation techniques, i.e. vitrification, encapsulation-vitrification and droplet-vitrification were compared for cryopreserving Sequoia sempervirens apical and basal buds sampled from in vitro shoot cultures. The effect of cold-hardening of mother-plants and of bud culture medium and sucrose preculture was also investigated. Culture of apical and basal buds sampled from cold-hardened mother-plants on Quoirin and Lepoivre medium with activated charcoal had a positive effect on regrowth. Only droplet-vitrification ensured survival and regrowth after cryopreservation. After cryopreservation, regeneration of apical buds was possible for PVS2 exposure durations between 90 and 180 min but it remained low, with a maximum of 18 percent after 135 min treatment. With basal buds, regeneration after cryopreservation was possible over a larger range of PVS2 treatment durations, between 30 and 180 min. The highest regeneration percentage was slightly higher (22 percent) than that measured with apical buds, and was also achieved after 135 min PVS2 exposure.