The preservation of pear germplasm, like that of other clonal germplasms, is difficult because it requires conservation of whole plants or their tissues. Among the currently available methods for long-term conservation of clonal germplasm, cryopreservation of shoot tips is the most reliable and cost- and space-effective option. Alginate-coated axillary shoot tips from in vitro−grown pear were conserved successfully in liquid nitrogen (LN) following dehydration. Shoot recovery from cryopreserved shoot tips was improved greatly after 8 weeks of cold acclimation, but recovery decreased slightly after then. The highest regeneration rate was observed when in vitro shoot tips were preincubated in MS (Murashige and Skoog) medium with 0.3 M sucrose for 48 h, and when alginate-coated shoot tips were precultured in MS medium with increasing sucrose concentrations (0.5 M and 0.7 M) for 8 and 16 h, respectively. When the encapsulated beads were dehydrated for up to 7 h [25% water content (fresh weight basis)] under laminar flow, the highest regeneration rate was observed in “BaeYun No. 3” (55.7%) and “Whanggeum” (43.3%) after warming from LN. This technique is useful as a practical procedure to cryopreserve plant material that is sensitive to freezing of the surrounding cryoprotectant medium. Therefore, this technique appears to be promising for the cryopreservation of shoot tips from in vitro−grown plantlets of pear germplasm.

Sweet potato (Ipomoea batatas L.) shoot tips grown in vitro were successfully cryopreserved by encapsulationvitrification. Encapsulated explants are very easily manipulated, due to the relatively large size of the alginate beads, and a large number of samples can be treated simultaneously. In this study, the effects of sucrose preculture, cryoprotectant preculture, and post-warm recovery media on regrowth, following liquid nitrogen (LN) exposure, were investigated to establish an efficient encapsulation-vitrification protocol for sweet potato. Shoot tips of plants grown in vitro were precultured in 0.3 M sucrose for 2 d before encapsulation. Encapsulated shoot tips were pre-incubated in liquid MS (Murashige and Skoog) medium containing 0.5 M sucrose for 16 h, before preculturing in sucrose-enriched medium (0.7 M sucrose) for 8 h. Shoot tips were osmoprotected with 35% plant vitrification solution 3 (PVS3) for 3 h, before being dehydrated with PVS3 for 2 h at 25°C. The encapsulated and dehydrated shoot tips were transferred to 2 mL cryotubes, suspended in 0.5 mL PVS3, and plunged directly into liquid N. High levels of shoot formation were obtained for the cv. Yeulmi (65.7%) and Yeonwhangmi (80.3%). The regrowth rates of cryopreserved samples in Yeulmi (78.9%) and Yeonwhangmi (91.3%), following culture on ammonium-free MS medium for 5 d, were much higher than those cultured on standard MS medium (65.7% and 80.3%, respectively). This encapsulation-vitrification is a promising method for the long-term preservation of sweet potato.