Gelled droplet vitrification improves recovery of cryopreserved potato germplasm.

The droplet vitrification method was improved for maneuverability by embedding shoot tips in gelled droplets before osmoprotection. This newly modified cryopreserving method -gelled droplet vitrification - was compared with other PVS2-based cryopreservation methods using potato shoot tips. Survival rates of each cryogenic procedure held at 25 degree C were about 40 percent by cryotube-vitrification procedures (vitrification and encapsulation vitrification methods) and about 70 percent by PVS2-droplet procedures (droplet vitrification and gelled droplet vitrification methods). Much higher cooling rates of PVS2-droplet procedures than cryotube- vitrification procedures increased their survival rates. The gelled droplet vitrification method was applied to shoot tips of 26 potato cultivars and six wild potatoes. After a little modifications of the conditions for preculture, osmoprotection and dehydration, all cultivars and wild potatoes produced high enough survival rates to be of value to genebanks and all surviving shoot tips developed normal shoots within 3 weeks.