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.

• JungYoon Yi(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)
• GiAn Lee(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)
• YoungYi Lee(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)
• JaeGyun Gwag(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)
• EunHo Son(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)
• HongJae Park(National Agrobiodiversity Center, NAAS, RDA, Suwon 16613, Korea)