Cryopreservation of in vitro-grown shoot-tips of hop (Humulus lupulus L.) using encapsulation/dehydration

A cryopreservation procedure using encapsulation/dehydration was establishe d for I;hoot-tips obtained from in vitro-grown shoots of hop. After dissect ion, shoot-tips were encapsulated in medium with alginate and 0.5 M sucrose . Optimal conditions consisted of preculture for 2 days in solid medium wit h 0.75 M sucrose, or in increasing sucrose concentrations, desiccation for 4 h with silicagel in a flow cabinet (16% water content) followed by rapid freezing and slow thawing. Shoot recovery after freezing 60 min in liquid n itrogen was around 80%. No phenotypical changes were observed in the recove red plants from cryopreserved shoot-tips growing in the field.