Cryopreservation of sour orange (Citrus aurantium L.) shoot tips

The objective of this study was to establish a cryopreservation protocol for sour orange (Citrus aurantium L.). Cryopreservation was carried out via encapsulation-dehydration, vitrification, and encapsulation-vitrification on shoot tips excised from in vitro cultures. Results indicated that a maximum of 83% survival and 47% regrowth of encapsulated-dehydrated and cryopreserved shoot tips was obtained with 0.5 M sucrose in the preculture medium and further dehydration for 6 It to attain 18% moisture content. Dehydration of encapsulated shoot tips with silica gel for 2 h resulted in 93% survival but only 37% regrowth of cryopreserved shoot tips. After preculturing with 0.5 M sucrose, 80% of the vitrified cryopreserved shoots survived when 2 M sucrose plus 10% dimethyl sulfoxide (DMSO) was used as a cryoprotectant for 20min at 25degreesC. Survival and regrowth of vitrified cryopreserved shoot tips were 67% and 43%, respectively, when 0.4 M sucrose plus 2 M glycerol was used as a loading solution followed by application of 100% plant vitrification solution (PVS2) for 20min. Increased duration of exposure to the loading solution up to 60min increased survival (83%) and regrowth (47%) of cryopreserved shoot tips. With encapsulation -vitrification, dehydration with 100% PVS2 for 2 or 3 h at 0degreesC resulted in 50 or 57% survival and 30 or 40% regrowth, respectively, of cryopreserved shoot tips.