| Abstract: | Increases in the number of cases of identified genetically modified(GM) rice contamination can be traced back to the first Rapid Alert System for Food and Feed(RASFF) in 2006. In response to the lack of reliable detection methods, Decision 2011/884/EU proposed that new screening methods replace Decision 2008/289/EC, to identify all possible GM rice products originating in China. However, the synergy brands(SYBR) Green real-time PCR assay proposed by Decision 2011/884/EU has been shown to lack conformity with other Taq Man methods currently in use. To evaluate the specificity and repeatability of the methods recommended in Decision 2011/884/EU and Decision 2008/289/EC, we collected 74 rice products originating from six countries or districts. The 74 rice samples were tested using the Decision 2011/884/EU and Decision 2008/289/EC methods. The parallel use of different instruments and reagents were used for testing in parallel, and the results were analyzed statistically. To avoid the limitations of specific laboratories, eight GM organism detection laboratories in China participated in a collaborative trial. In our tests, 24.3%(18/74) of the samples tested were positive with the SYBR Green real-time PCR assay using the Decision 2011/884/EU method, but were negative with the Taq Man real-time PCR assay using the Decision 2011/884/EU and Decision 2008/289/EC methods. Sequencing the PCR-amplified Cry IA(b/c) genes in three samples(6, 30 and 43) showed that the products consisted of primer dimers rather than the targeted sequence. The combined experimental results showed that testing for the nopaline synthase gene(NOS) of Agrobacterium tumefasciens terminator and Cry IA(b/c) produced false-positive results when the Decision 2011/884/EU method was used. Because of the high rate of false-positive results, the Decision 2011/884/EU SYBR Green method to detect GM rice requires improvement. |
