Cryopreservation by encapsulation-dehydration for long-term storage of some important germplasm: seed of lily [Lilium ledebourii (Baker) Bioss.], embryonic axe of persian lilac (Melia azedarach L.), and tea (Camellia sinensis L.)

Cryopreservation of germplasm in liquid nitrogen (LN) is a perfect method for the long-term conservation of plant genetic resources. Lily [Lilium ledebourii (Baker) Bioss.], Persian lilac (Melia azedarach L.), and tea (Camellia sinensis L.) were evaluated for long-term storage in liquid nitrogen (LN) at -196oC. Encapsulation within alginate beads was shown to be beneficial in all studied species. Embryonic axes of M. azedarach L. and C. sinensis L. and seeds of L. ledebourii (Baker) Bioss. were encapsulated in MS medium supplemented with 3% Na-alginate, 100 mM CaCl2 and 0.75 M sucrose and desiccated for 1 h under the laminar air flow. Embryonic axes and seeds were plunged into LN and held for at least 1 h. Following cryopreservation, embryonic axes and seeds were cultured on solid Murashige and Skoog (MS) medium. In M. azedarach L., survival rate after freezing was zero, for non-pretreated and non-encapsulated embryonic axes, also nil for pretreated and non-encapsulated embryonic axes, and 42% for pretreated and encapsulated embryonic axes. In C. sinensis L., non-encapsulated embryonic axes, even those pretreated with sucrose and dehydration, did not survive at all. However, pretreated and encapsulated embryonic axes may offer a better resistance after exposure to LN. In L. ledebourii (Baker) Bioss., control seeds did not survive after LN treatment. The rate of viability in non-encapsulated seeds pretreated with sucrose and dehydration was 75%. The rate of viability in pretreated, encapsulated seeds was 50%. In general, application of sucrose, dehydration and encapsulation can be suitable to increase tolerance of tissues to very low temperature (-196oC) and be used as improved technique of cryopreservation in an extent number of species.