CRYOPRESERVATION OF FRUIT-TREE SOMATIC EM BRYOS AND SHOOT TIPS

An improved survival of somatic embryos and shoot tips of fruit trees (coffee, pear, apple and peach) after storage in liquid nitrogen was o btained, using various procedures. Conventional procedures involved pr eculture with sucrose, using enriched preculture media, loading with d imethylsulfoxide, using freeze-induced cell dehydration, cooling in li quid nitrogen and rapid thawing. For coffee, secondary embryogenesis r ecovery depended on sucrose and dimethylsulfoxide concentrations in pr eculture and loading media. High recovery rates of frozen pear and app le shoot tips were obtained after cold hardening of in vitro donor pla nts. In the encapsulation-dehydration procedure, shoot tips were encap sulated in alginate beads, dehydrated under a sterile air flow at room temperature, directly cooled in liquid nitrogen and rewarmed slowly i n air. Shoot recover was dependent on cold hardening of donor in vitro plantlets and preculture in sucrose-enriched medium but was not affec ted by the duration of storage at -196-degrees-C or -70-degrees-C. Thi s procedure was applied to 17 cultivars of apple and pear. Shoot recov ery remained high. The encapsulation-vitrification procedure consisted of loading and osmotic dehydration by exposure of encapsulated organs (shoot tips of apple and peach) to concentrated mixtures of penetrati ng and non- or low-penetrating cryoprotective agents.