a1 Tissue Culture and Cryopreservation Unit, National Bureau of Plant Genetic Resources (NBPGR), Pusa Campus, New Delhi, 110012, India
The cryopreservation of embryonic axes of two wild and endangered species, Citrus macroptera Mont. and C. latipes Tanaka, was attempted using air desiccation–freezing, vitrification and encapsulation–dehydration. Successful cryopreservation was achieved in both the species using these three methods. However, the two species responded differently to: the rate of drying and the degree of tolerance to desiccation following air desiccation–freezing; the response to loading duration following vitrification; and to the sucrose concentration during pre-culture following encapsulation–dehydration. C. macroptera was more tolerant to desiccation and freezing than C. latipes with recovery rates of, respectively, 87% and 64%. Recovery from encapsulation–dehydration was 62% for C. macroptera and 45% for C. latipes. In both species, the vitrification protocol gave a significant improvement in recovery rates: 92% and 77% for C. macroptera and C. latipes, respectively. The air desiccation–freezing protocol being a simple and practical technique is recommended for the cryopreservation of these two species.
(Received October 31 2005)
(Accepted March 31 2006)