The paper describes one of the studies to address the need of researchers, private companies, and Philippine government regulatory units, for protocols to detect transgenes inserted into genetically modified crops. PCR-based detection of a native corn gene and transgenes inserted into three kinds of genetically modified (GM) corn (Zea mays L.), including Yieldgard® MON810, Roundup Ready® GA21, and Roundup Ready® NK603, was achieved using primers that amplify fragments of zein (native corn gene), CamV 35S (cauliflower mosaic virus promoter), cry1Ab (gene for the insecticidal protein, Cry1Ab, derived from Bacillus thuringiensis), OTP/mepsps (gene for optimized chloroplast transit peptide and the modified plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase, respectively), r-act pro (the rice actin promoter), and nos (nopaline synthase transcriptional termination element from Agrobacterium tumefaciens). Fragments of three genes zein (329-bp), CamV 35S promoter (220-bp), and the cry1Ab (194- bp) were detected by multiplex PCR from GM corn Yieldgard® MON810. Multiplex PCR amplified a fragment of the OTP/mepsps gene (270-bp), in addition to the fragments of the zein gene (329-bp) and the nos terminator (151-bp) in the GM corn Roundup Ready® GA21. In the Roundup Ready® NK603 GM corn, multiplex PCR detected fragments of zein (329-bp), camV 35S promoter (220-bp) and nos terminator gene (151-bp).
The study showed that a fragment of the rice actin promoter (408-bp) which could not be amplified in multiplex PCR, was detected in single PCR using DNA template from both Roundup Ready® GA21 and Roundup Ready® NK603. Multiplex PCR could detect the presence of target gene fragments in DNA extracted from seed samples containing as low as 0.1% (0.1g GM/99.9g non-GM IPBVar1) or 1.0% (1.0g GM/99g non-GM IPBVar1) GM corn seeds.