CRYOPRESERVATION OF SHOOT PRIMORDIA CULTURES OF MELON USING A SLOW PREFREEZING PROCEDURE

Tissue-cultured shoot primordia of melon (Cucumis melo L. cv. prince m elon) were successfully cryopreserved in liquid nitrogen (LN) using a slow prefreezing method. The highest survival and recovery were obtain ed with the following procedure. Three week-old shoot primordia clumps were dissected into pieces of 2-3 mm of diameter and precultured in s tandard medium for 3 days. They were directly soaked in CSP1 cryoprote ctive solution (10%w/v sucrose, 10%w/v dimethylsulfoxide and 5%w/v gly cerol) and incubated at room temperature for 30 min. Samples were ice- inoculated at -8 degrees C and cooled at a rate of between 0.3 and 1 d egrees C min(-1) with a programmable freezer to -30 degrees C for pref reezing. They were then plunged into LN for storage. After rapid thawi ng in 40 degrees C water, the cryoprotective solution was slowly dilut ed 5 fold in a dropwise manner with 3% sucrose and the shoot primordia were transferred onto regeneration medium. Under optimal conditions, more than 80% of cryopreserved shoot primordia were viable and 50 to 8 0% regenerated shoots after one month of reculture. Cryopreserved shoo t primordia could be used both for reproducing a shoot primordia cultu re and for regenerating plants.