Development of a gene transfer system will enable rapid introduction of agronomically useful genes into elite cultivars of sweet potato. We compared microprojectile bombardment and Agrobacterium cocultivation approaches to introduce foreign genes into the genome of two sweet potato cultivars. Chimeric marker genes (gusA and kan) were successfully introduced into cvs. Jewel and TIS-70357 using both approaches. However, transgenic plants were generated in vitro using only the Agrobacterium approach. Callus and root isolates with stable expression of gusA gene were obtained using the microprojectile method. Expression of the screenable marker gusA gene was detected by histochemical assays. Integration of the introduced gene into the genome of sweet potato was confirmed by polymerase chain reaction (PCR) amplification of the kan gene and Southern blot analyses. Transgenic sweet potato plants from two cultivars are being raised and studied for quantitative expression and localization of the introduced genes. These results show that foreign genes can be successfully introduced and expressed in sweet potato. Current efforts are directed at optimizing several variables to increase the transformation efficiencies and to generate transgenic cultivars with foreign genes of agricultural importance.
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