Cryopreservation of sweet potato (Ipomoea batatas [L.] Lam.) shoot tips by vitrification.

Vitrification is a technically simple method for cryopreserving plant germplasm, requiring only the application of suitable cryoprotectants and rapid cooling rates. Sweetpotato (Ipomoea batatas [L.] Lam.) shoot tips obtained from in vitro plants survived liquid nitrogen (-196°C) exposure following a vitrification-inducing pretreatment. Shoot tips were treated in a stepwise manner with a vitrification solution containing 30% glycerol, 15% ethylene glycol and 15% dimethylsulfoxide in growth medium. Incubation of shoot tips for 1 to 2 h in low concentrations of the vitrification solution enhanced survival. Most surviving shoot tips developed callus, and a variable percentage subsequently formed shoots. Survival was not achieved using two-step cooling procedures. The percentage of shoot tips surviving vitrification and those subsequently forming a shoot varied widely among replications.