In vitro Conservation and Cryopreservation of Nandina domestica, an Outdoor Ornamental Shrub

Abstract

The study focused on an economically-important ornamental outdoor shrub, Nandina domestica, with the aims to (i) optimize an effective in vitro conservation method, and (h) develop a cryopreservation protocol for shoot tips by the PVS2 vitrification and dropletvitrification techniques. For in vitro conservation of shoot cultures, the tested parameters were sucrose content in the storage medium (30, 45, 60 g/L) and storage temperature (4 degrees C or 8 degrees C). Cryopreservation was performed by applying the PVS2 vitrification solution, in 2-ml cryovials or in drops over aluminum foil strips, for 15, 30, 60 or 90 mm at 0 degrees C, followed by the direct immersion in liquid nitrogen of shoot tips. Results showed that N. domestica can be conserved successfully for 6 months at both the temperatures tested, especially when of shoot tipe 60 g/L sucrose is used in the storage medium. However, conservation at 4 degrees C showed to be more appropriate, as hyperhydricity was observed in post-conservation of shoots coming from storage at 8 degrees C. As for cryopreservation, a daily gradual increase of sucrose concentration (from 0.25 to 1.0 M) produced better protection to the samples that were stored in liquid nitrogen. Indeed, with this sucrose treatment method, a 30-min PVS2 incubation time was enough to produce, 60 days after thawing, the best recovery (47% and 50%) of shoot tips, cryopreserved with PVS2 vitrification and droplet-vitrification, respectively.