Yj. Wu et al., Cryopreservation of apple shoot tips: Importance of cryopreservation technique and of conditioning of donor plants, CRYO-LETT, 20(2), 1999, pp. 121-130
In this gaper, the efficiency of three techniques (two-step freezing, vitri
fication, encapsulation-dehydration) for freezing irt vitro shoot tips was
compared and the effect of conditioning of mother-plants was investigated.
Cold-hardening mother plants for 3 weeks at 5 degrees C improved regrowth r
ate and pattern of shoot tips whatever the cryopreservation technique emplo
yed. Increasing the time during which mother-plants were maintained on stan
dard medium without subculture before sampling of apices decreased the wate
r content of shoot tips from about 85-88% to 63-66% (fresh weight basis) an
d increased regrowth rate and pattern whatever the cryopreservation techniq
ue employed. The best results (up to 86% regrowth after cryopreservation wi
thout any callusing) were obtained with the encapsulation-dehydration techn
ique. Using apices sampled on mother-plants which had not been subcultured
for 26 weeks allowed to reduce the duration of the sucrose pregrowth treatm
ent of encapsulated apices, thus simplifying the protocol. This simplified
encapsulation-dehydration protocol was successfully applied to II out of th
e 12 cultivars tested.