Cryopreservation of Winter-dormant Apple Buds IV: Critical Temperature Variation that Can Compromise Survival

Precise temperature control in several key areas during cryopreservation of dormant, winter apple buds is critical for maximal survival.To consider the effects of pre-harvest temperature, the duration of incubation at -30°C and variation in rewarming rate on survival.Dormant winter buds of Malus x domestica cultivars were harvested with two different acclimation histories and cryopreserved with variation in incubation time at -30°C. Recovery from LN using slow, intermediate and rapid rewarming was investigated as well as preservation after prolonged storage at -4°C.The effects on survival of preharvest temperature regime and an altered -30°C incubation regime are cultivar dependent and an increase in rewarming rate has a strong negative effect on recovery.Post-thaw survival of the winter-dormant buds can be compromised by increased temperature over a period as short as 5 days prior to bud harvest. Varying incubation times at -30°C produce variable, cultivar dependent, survival and moderate increases in rewarming rates can also radically reduce survival.