Plant cell cultures consist of single cells or cell clusters growing as callus or suspension. Such cell cultures may be able to produce secondary metabolites and/or possess embryogenic potential. Therefore, they can be used for very different purposes in research, biotechnological applications, as well as for plant propagation. Cryopreservation is the only practical method to preserve such cultures until they are needed. Different cryopreservation approaches that have been developed for differentiated plant tissues including slow freezing, vitrification, and encapsulation/dehydration have also been applied to plant cell cultures. The controlled rate or slow-freezing approach, however, remains to be the gold standard for cell cultures. In this chapter, a standard slow-freezing cryopreservation procedure in combination with alginate immobilization is presented for long-term preservation of plant cell cultures.
Keywords: Alginate; Callus culture; Controlled rate freezing; Dedifferentiated; Embryogenic; Immobilization; Slow freezing; Suspension culture.