A PCR method to detect different Bt gene expression cassettes in transgenic Bt cotton.

The Bt gene expression cassettes of two GM cotton(Gossypium hirsutum L.) varieties were sequenced and analyzed.Differences were found between these two cotton varieties in both the Bt gene and the junction region of Bt gene/terminators except the junction region of CaMV 35S promoter/Bt gene.In order to distinguish the two different Bt gene expression cassettes, three specif-ic primers, MG-P1, MG-P2 and MG-P3, were designed and the duplex PCR detection method was established based on the differ-ences.Results showed that among 40 transgenic cotton samples tested by this duplex PCR method, 38 samples were identified to have single Bt gene expression cassette structure, and two samples were identified to have both the Bt gene expression cassettes structures.