CBN-V Video Archives - S7-31
Transgenic Cassava Plants Containing a Defective Interfering (DI) Particle have Elevated Resistance to African Cassava Mosaic Disease

Taylor N.J., M.V. Masona, F. Ogbe, C.M. Fauquet

International Laboratory for Tropical Agricultural Biotechnology (ILTAB), Danforth Plant Science Center, 975 Warson Road, St Louis, MO 63132 iltab@danforthcenter.org

        Heterozygosity and inbreeding depression complicate conventional breeding in cassava (Manihot esculenta) and make genetic engineering an attractive technology for integrating beneficial traits directly into elite germplasm. A major goal has been to employ transgenic technologies to increase resistance to African cassava mosaic disease, the single most important biotic constraint to cassava production in sub-Saharan Africa. Friable embyrogenic callus of cv. TMS 60444 was genetically transformed by co-bombardment with the nptII selectable marker and a dimer of the defective interfering (DI) particle from a Kenyan strain of African cassava mosaic virus (ACMV). Forty transgenic callus lines were recovered from which nineteen plant lines were regenerated, fifteen of which were PCR positive for presence of the DI sequence. All plants were established in the greenhouse. DI transgenic plants were challenged by particle bombardment with infectious clones of ACMV and East African cassava mosaic virus. Evidence will be presented that the DI fragment is mobalised in the presence of viral DNA and that this is correlated to delayed symptom apparition and enhanced resistance to geminivirus infection in the transgenic lines. The most promising plant lines are now being prepared for field trail in West and East Africa. The logisitics and prospects for deploying this technology in Africa will be discussed.

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