Cryopreservation of Cold-tender Apple Germplasm

Unlike cold-hardy apple germplasm, dormant vegetative buds from cold-tender accessions require stabilization of meristematic tissue to protect against injury during desiccation and cryopreservation. Dormant buds of six apple cultivars [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Cox's Orange Pippin', `Einshemer', `Golden Delicious', `Jonagold', `K-14', and `Mutsu'] collected at specific intervals in 1993, 1994, and 1995 at Geneva, N.Y., were stabilized by encapsulation in 5% alginate, treated with step-wise imbibition of 0.5 to 1.0 m sucrose and 0.2 m raffinose solution, and desiccated with forced air at 0 °C. Sugar-alginate stabilization reduced injury during desiccation, increased cold-hardiness of the six cold-tender cultivars frozen to -30 °C, and improved recovery following cryopreservation of buds collected before optimal cold acclimation was attained. Sucrose tissue levels did not increase following stabilization treatment, but levels of glucose and fructose, and of an unknown disaccharide increased. This procedure used nontoxic cryoprotectants, and has potential to expand the scope of dormant bud cryopreservation to include cold-tender apple germplasm.