Reliable Production of Transgenic Cassava Plants Mediated by Agrobacterium tumefaciens

Transformed cassava plants were successfully produced from friable embryogenic calli derived from leaf lobes by Agrobacterium tumefaciens-mediated transformation. We used A. tumefaciens strain LBA4404 containing pCAMmPHY which contained a binary vector with genes for β-glucuronidase (GUS) as a reporter and neomycin phosphotransferaseII (NPTII) for selection. Transformed calli and plantlets were selected on medium containing 20 or 30 mg l⁻¹ geneticin, respectively. At each selection step, GUS activity in transformants resistant to geneticin was histochemically assayed. Southern blot analysis showed that seven independent transgenic plants were identified and one to four copies of the transgenes was integrated into the cassava genome. RT-PCR confirmed GUS expression in the transgenic cassava. A leaf bleach assay by application of paromomycin showed that the NPTII gene was functionally expressed in the transgenic cassava plants.