Development of a cryopreservation procedure for peanut (Arachis hypogaea L.) embryonic axes and its application to local Turkish germplasm

Effective one-step freezing procedures, based on either vitrification or dehydration of embryonic axes, were optimized for the cryopreservation of Arachis hypogaea subsp. hypogaea L., cv. Virginia, and then tested with three Turkish cultivars belonging to the same subspecies. The best vitrification protocol included preloading of embryonic axes with 2 M glycerol and 0.4 M sucrose for 30 min, followed by treatment with PVS2 for 2 hr at 250C and by direct immersion in liquid nitrogen. The best dehydration protocol involved a 2.5-hr desiccation in the sterile air current of a laminar flow cabinet, which reduced the initial moisture content of 'Virginia' embryonic axes from 25% to 8.5%, prior to ultra-rapid freezing. With these procedures, maximums of 80% and 100% germinability of 'Virginia' embryonic axes were achieved, respectively. Considerable callus proliferation and poor root development were observed at the base of germinating embryos treated with PVS2. Following cryopreservation, a growth regulator-free MS medium was shown to be the most effective in stimulating embryonic axes germination and seedling development. Both the protocols optimized for the cv. Virginia were excellent also when applied to the cryopreservation of Turkish germplasm, resulting in germination percentages of 53-87% (vitrification procedure), and 75-92% (dehydration procedure). The dehydration/one-step freezing procedure confirmed its superiority in terms of quality of the developing seedlings.