Recovery and longevity of cryopreserved dormant apple buds

Clonally propagated crops, unlike seed-propagated crops, require intense and costly maintenance, generally in ex situ field gene banks. Consequently, large germplasm collections of tree species especially, are difficult to conserve in a well-replicated fashion and are vulnerable to damage from environmental stresses. Accordingly, long-term storage in liquid nitrogen presents a viable conservation alternative. To assess effectiveness of one approach to cryopreservation, dormant buds from 64 apple (Malus x domestica Borkh. and other Malus spp.) accessions were collected and preserved in liquid nitrogen using a dormant-vegetative-bud method. Buds were retrieved from liquid nitrogen storage, rehydrated, and grafted onto rootstocks to determine survival. Mean recovery was 76% for 40 cold-hardy accessions, 66% for 20 moderately cold-hardy accessions, and 24 % for four cold-tender accessions (range: 16% to 100 %). Only four accessions had less than or equal to 25% recovery while 54 accessions had less than or equal to 50% recovery and 35 accessions had less than or equal to 75% recovery. No significant decline in recovery of these accessions by bud grafting occurred after 4 years of liquid nitrogen storage.