Comparison of droplet-vitrification and D-cryoplate for cryopreservation of date palm (Phoenix dactylifera L.) polyembryonic masses

Abstract

In this work we tested the efficiency of two techniques, droplet-vitrification (DV) and dehydration (D) cryo-plate, for cryopreservation of polyembryonic masses (PEMs) of two date palm varieties, Sokary and Sultany. With DV, recovery of non-precultured, cryopreserved PEMs was nil without treatment with the PVS2 vitrification solution, which contained 3.3M glycerol+2.4M ethylene glycol+0.4M sucrose+1.9M dimethylsulfoxide. Following PVS2 treatments between 15 and 120min, it was comprised between 90.9–98.6% and 85.6–88.0% for varieties Sokary and Sultany, respectively. Sucrose preculture (3 days, 0.5M) led to 21.1% recovery of cryopreserved PEMs of variety Sokary only without PVS2 treatment, and slightly reduced recovery in all other experimental conditions with both varieties, compared with non-cryopreserved PEMs. Regrowth intensity of cryopreserved PEMs was generally lower with variety Sultany compared to variety Sokary. With the D cryo-plate technique, no recovery of cryopreserved PEMs was achieved without sucrose preculture. Sucrose preculture (3 days, 0.5M) had a positive effect on recovery of cryopreserved PEMs. For variety Sokary, the highest recovery (92.0–95.8%) was achieved for desiccation periods between 60 and 120min. Recovery was between 67.0 and 74.6% after desiccation periods of 90–120min for variety Sultany. With the D cryo-plate technique, regrowth intensity of cryopreserved PEMs was higher with variety Sokary compared to variety Sultany.