Cryopreservation of Date Palm (Phoenix dactyli/era) Embryogenic Callus by Encapsulation-Dehydration, Vitrification and Encapsulation-Vitrification

Cryopreservation of date palm (Phoenix dactylifera) embryogenic callus via encapsulation-dehydration, vitrification and encapsulation-vitrification was investigated. High survival (80%) out of the encapsulation- dehydration method was obtained when cryoprserved calli were pretreated with 0.3 sucrose for 2 days followed by 2 h of dehydration. The highest (33.3 or 40%) regrowth was obtained with 0.1 M sucrose after 2 h or 4 h of dehydration; with 0.3 M sucrose after 2 h of dehydration; or with 0.5 M sucrose after 4 h of dehydration. Viability of calli decreased with increasing sucrose concentration and dehydration period. In vitrification, direct exposure of calli to 100% Plant Vitrification Solution 2 (PVS2) decreased the viability of calli. Survival of 80- 93.3% and 40-53.3% regrowth rates were achieved with two- or four- step dehydration, using PVS2 at 25 ̊C for 20 min intervals prior to freezing. Cryoprotection by using 1.0 M sucrose plus 15% Dimethyle Sulfooxide (DMSO) and dehydration using 2.0 M glycerol plus 0.4 M sucrose or 0.5 M sucrose plus 10% DMSO all produced 60 or 66.7% survival rates after freezing. In encapsulation-vitrification, cryopreservation of encapsulated calli after treatment with 100% PVS2 (at 25 ̊C for 5 to 10 min) resulted in 60% survival and there were no differences in regrowth rates (ranging between 20 to 33.3%) in response to PVS2 dehydration period (5 to 90 min.).