Sweetpotato Transformation Mediated by Agrobacterium tumefaciens

Transformed sweetpotato plants were successfully produced from 6 month old embryogenic calli induced from shoot apical meristem using Agrobacterium tumefaciens-mediated transformation method. The plant expression vector used in the study contained GUS gene and NPTII for selection under the control of CaMV35S promoter. Transformed calli and plantlets were selected on G₄₁₈-containing media. In order to determine GUS gene expression, a piece of calli or plantlets were histochemically assayed. Six transgenic plants were confirmed by PCR. By Southern blot analysis, three plants had the same pattern of band mobility, meaning that these three lines were identical. Thus, four independent transgenic plants were identified and a single or two copies of transgenes were integrated into the sweetpotato genome. Using leaf assay, transgenic sweetpotato plants showed resistance to paromomycin, indicating that NPTII gene incorporated in the sweetpotato genome was functionally expressed in sweetpotato plants. Histochemcially GUS positive plants showed resistance to paromomycin, indicating that both genes in T-DNAs were functionally expressed in transgenic sweetpotato without silencing. The transgenic sweetpotato plants appeared to be morphologically normal compared to wild type plant.