Medium alterations improve regrowth of sweet potato (Ipomoea batatas [L.] lam.) shoot tips cryopreserved by vitrification and encapsulation-dehydration.

In vitro grown sweet potato (Ipomoea batatas [L.] Lam.) shoot tips were successfully cryopreserved by both solution based and encapsulation-dehydration vitrification methods. Improved recovery medium enhanced recovery for both vitrification procedures. The effects of sucrose preculture, cryoprotectant preculture and post-warm recovery media on regrowth following LN exposure were investigated. Sucrose preculture was critical for the survival of sweet potato shoot tips cooled to ca. -200 degrees C. Cryoprotectant preculture with 2 M glycerol + 0.4 M sucrose before dehydration with PVS2 gave the highest recovery following LN exposure. The viability of cooled samples following culture on ammonium-free MS medium for 5 days was increased three-fold over those cultured on MS medium. The improvement in recovery by altering post-warming conditions suggests that cryoinjury is not always lethal and can be ameliorated by suitable culture conditions.