Cryopreservation of encapsulated sugarcane apices: Effect of storage temperature and storage duration

Apices sampled on in vitro plantlets of sugarcane were cryopreserved using the encapsulation-dehydration technique, comprising pregrowth for 24 h in l iquid medium with 0.75 M sucrose, desiccation to 20-25% moisture content (f resh weight basis) and rapid immersion in liquid nitrogen. Apices of one va riety were stored for up to one year at -196 degrees C, -70 degrees C or -2 5 degrees C, with or without previous transitory immersion in liquid nitrog en. Whereas the recovery percentage of apices stored at -196 degrees C rema ined high and constant throughout the experiment, recovery of apices conser ved at -70 degrees C and -25 degrees C decreased dramatically within 0.5 da y, and was nil after 10 or 120 days in storage at -25 degrees C and -70 deg rees C, respectively. The recovery percentage of apices of four additional varieties remained stable throughout a 1 year storage period at -196 degree s C. No differences were noted for 6 agronomic traits between plants regene rated from control and cryopreserved apices of two sugarcane varieties.