CRYOPRESERVATION OF IN VITRO-GROWN APICAL MERISTEMS OF WASABI (WASABIA-JAPONICA) BY ENCAPSULATION-VITRIFICATION METHOD

Alginate-coatcd apical meristems from in vitro-grown wasabi (Wasabia japonica Matsumura) were successfully cryopreserved following dehydration by vitrification solutions. Excised meristems precultured oil solidified 1/2 MS medium containing 0.3 M sucrose at 20 degrees C for 1 day were trapped into alginate-coated beads containing a mixture of 2 M glycerol plus 0.4 M sucrose. These encapsulated meristems were dehydrated with a highly concentrated vitrification solution (designated PVS2 or PVS3) for about 30 min at 25 degrees C or 70 to 100 min at 0 degrees C prior to a plunge into liquid nitrogen. Successfully encapsulated vitrified meristems resumed growth within 3 days and the average rate of shoot formation amounted to about 95%. The rate of shoot formation of encapsulated vitrified meristems was higher by as much as 30% than the meristems cryopreserved by the encapsulation-dehydration technique. Besides, the recovery growth was much earlier than the latter. The encapsulation-vitrification method is easy to handle and saves greatly the time used for dehydration. Thus, the encapsulation-vitrification method promises for cryopreserving meristems.