CBN-V Video Archives - S7-23
Cryopreservation for Long-term Conservation of Cassava Germplasm

Ng S.Y.G., N.Q. Ng and M.O. Ojo

International Institute of Tropical Agriculture (IITA), Oyo Road, Ibadan, Nigeria s.ng@cgiar.org

        IITA holds a collection of about 2500 accessions of cassava germplasm and related wild species. The collection is maintained in the field: about 25% are duplicated in vitro under reduced growth conditions. Both methods require periodic re-planting or sub-culturing of the conserved germplasm. Cryopreservation may offer a method for long-term conservation. Various factors that affect the survival and recovery rates of cassava shoot apexes after cryopreservation in liquid nitrogen, using vitrification and fast freezing were investigated. These include pre-conditioning of the donor plants, pre-culture of the shoot apexes, and time exposure of apexes to the vitrification solution. Results showed that highest percentage survival and recovery were obtained in shoot apexes treated with a vitrification solution for 30 to 50 minutes before they were plunged into liquid nitrogen. Shoot apexes excised from donor plants growing in 5% sucrose culture medium gave higher survival and recovery rates than shoot apexes from plants growing in 3% sucrose culture medium. A high percentage of plant recovery (60%) was achieved in shoot apexes pre-cultured in 0.4 M sucrose culture medium for 4 days before being processed and stored in liquid nitrogen. Based on these results a protocol has been established for the cryopreservation of cassava shoot apexes at IITA and is being tested on a wide range of genotypes for application in the long-term conservation of cassava germplasm.

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