Long-Term Storage of Fraser Photinia Shoot Tips via Conventional and Droplet Vitrification Techniques

Abstract

Conventional vitrification and droplet vitrification techniques were tested for cryopreservation of shoot tips of in vitro grown fraser photinia. Relatively higher regrowth percentages were obtained in cryopreserved shoot tips with droplet vitrification technique. The optimised droplet vitrification technique consists of excision of shoot tips from cold-hardened shoots (8 weeks at 4 degrees C), preculture in MS semi-solid medium containing 0.5 M sucrose (3 days at 25 degrees C), osmoprotection with loading solution (30 min at 25 degrees C), dehydration in a small amount of PVS2 droplet (120 min at 0 degrees C), followed by rapid cooling in liquid nitrogen on aluminium foil strips for at least 1 h. Then cryopreserved samples were rapidly warmed by direct dipping of the aluminium foil strips into unloading solution containing 1.2 M sucrose and then shoot tips were transferred directly to Quoirin and Lepoivre (QL) culture medium containing 1 mg L-1 BA. The optimised droplet vitrification protocol improved the mean regrowth percentages of fraser photinia to 27.3% from 12.5% obtained with previously reported encapsulation-dehydration protocol.