Cryopreservation of Fagus crenata seeds: estimation of optimum moisture content for maintenance of seed viability by Bayesian modeling

Fagus crenata Blume is an important forestry tree species that plays a key biological role in natural forests. Because F. crenata forests are declining under global warming, the conservation of seed resources is necessary to maintain sustainable regeneration. We examined the capability of seed cryopreservation to achieve semi-permanent preservation of the F. crenata genetic resource. Seeds at 7%-26% moisture content (MC) exhibited greater than 64% viability, with developing radicles growing at 22 degrees C in 16 h photoperiods following chilling at 2 degrees C for 2 months. These seeds were then stored cryogenically at -170 degrees C for 6 months; cryopreservation at 26% MC reduced seed viability to 12%, whereas dry seeds (7%-14% MC) maintained viability and were comparable with seeds that had neither been dried nor cryopreserved. Drying seeds to 6% MC reduced viability to 47%; following cryopreservation, the viability of these seeds with such a low MC was 36%. Using a Bayesian model, we then determined that the optimal range of MC for the cryopreservation of F. crenata seeds was 9%-12%. We conclude that cryopreservation is feasible for the long-term storage of F. crenata seeds, drying of the seeds to the range of optimal MC retains high viability during cryogenic storage.