Monitoring the prevalence of genetically modified soybeans in tofu in Chengdu, China using real-time and conventional PCR

Abstract

Owing to the variability in theCP4-EPSPS sequence between the 1st and 2nd generation of genetically modified (GM) herb-tolerant soybean, existing PCR methods were not able to detect the CP4-EPSPS gene in the 2nd generation. Here, we developed a novel real-time PCR method for the detection of the CP4-EPSPS gene. In total, 101 tofu products from family workshops or vendors in 17 local farmers’ markets in Chengdu, China, were collected and analyzed, for the first time, for the presence of GM organisms (GMOs) using real-time and conventional PCR methods The real-time PCR method established here showed a high specificity and a sensitivity of 5 copies. Among the 101 tofu samples, 68 (67%) tested positive for the CP4-EPSPS gene, or at least 1 of 6 transformation events, suggesting that a large number of GM components present in tofu products in the Chengdu markets. However, none of the GM-positive samples was labeled as containing GMOs, as required by labeling regulations in China. Because of the relaxed control of the local administrative department, the GM soybeans imported for consumption are very possibly being illegally dispersed. Therefore, there may be an ecological risk to the species diversity of cultivated soybeans in local environments.