Cryopreservation of kiwi shoot tips.

In this study, the effect of various factors, including the physiological state of mother-plants and parameters of the encapsulation-dehydration protocol (cryoprotective treatment, freezing protocol) on the regrowth of shoot tips of kiwi in vitro plantlets was studied. The optimal protocol established was the following: shoot tips were sampled on mother-plants after a one month cold-acclimation period at 5 degrees C. For preculture, which was performed at 5 degrees C, encapsulated shoot tips were transferred at 24-hour intervals on solid media with increasing sucrose concentrations, from 0.5 to 1.0M. Beads were then desiccated to 26% moisture content (fresh weight basis), prefrozen from 0 degrees C to -40 degrees C at 0.2 degrees C/min and immersed rapidly in liquid nitrogen. No differences were noted between in vitro plantlets produced from cryopreserved and control shoot tips as regards leaf color, average height, multiplication rate and peroxidase zymogram pattern. Apices of 3 kiwi accessions were frozen using the above protocol with regrowth percentages ranging between 22 and 56%.