The contamination of processed vegetable foods with genetically modified tomatoes was investigated by the use of qualitative PCR methods to detect the
cauliflower mosaic virus 35S promoter (P35S) and the kanamycin resistance gene (
NPTII). DNA fragments of P35S and
NPTII were detected in vegetable juice samples, possibly due to contamination with the genomes of
cauliflower mosaic virus infecting juice ingredients of
Brassica species and soil bacteria, respectively. Therefore, to detect the transformation construct sequences of GM tomatoes, primer pairs were designed for qualitative PCR to specifically detect the border region between P35S and
NPTII, and the border region between nopaline synthase gene promoter and
NPTII. No amplification of the targeted sequences was observed using genomic DNA purified from the juice ingredients. The developed qualitative PCR method is considered to be a reliable tool to check contamination of products with GM tomatoes.
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