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Government Chemist works to improve GM Rice testing

10 Jun 2013
The Government Chemist Programme, in LGC, has authored a paper[1] outlining the first available control material to help labs check for false positives when policing imports for genetically modified (GM) rice in food products originating from China.
European law requires laboratory tests for all imported rice consignments and there are currently no GM rice varieties approved for use in the EU but reportedly over 25 varieties that may be a source of contamination .
Dr Malcolm Burns, one of the authors of the paper, said, “Testing for unauthorised GM rice is a complex undertaking and we need to be able to provide assurance that we can prove contamination is present beyond reasonable doubt. This is important not only for consumer confidence but also for the courts, regulators and food businesses. A false positive would mean destroying perfectly good rice. The control material we have developed means that for the first time labs can easily check that their work to avoid false positives is on a sound basis.”
An elaborate process is in place to assess the safety of GM food in the EU and give consumers choice over what they eat. All rice consignments imported into the EU from China are tested for the presence of specific molecular markers associated with genetic modification and when detected consignments must be re-dispatched to the country of origin or destroyed.
The P-35S promoter sequence, derived from Cauliflower Mosaic Virus (CaMV), is one of the genetic elements routinely screened for to infer the presence of GM rice. But this sequence is also present in naturally occurring Cauliflower Mosaic Virus, which can infect plants (such as cauliflower and turnip) affecting plant growth, though it is important to point out that it is harmless to humans.
Thus, to ensure that finding the P-35S promoter sequence implies that a consignment is contaminated with unauthorised GM rice, laboratories need to check that it is not a false positive from naturally occurring Cauliflower Mosaic Virus. Until now there was no straightforward way of verifying that the tests for the natural virus worked properly in the lab, but in this paper Dr Malcolm Burns and colleagues have reported a suitable control material. A specific DNA sequence from CaMV has been synthesised and inserted into a standard plasmid to provide a suitable control and tested using a validated and EU approved real-time PCR assay. The team was successful in amplifying the DNA target in the CaMV plasmid control with a limit of detection of approximately four copies of the plasmid target.
The full paper is now freely available (open access) from the Journal of the Association of Public Analysts (JAPA) here.

[1] Malcolm Burns, Gavin Nixon, Michael Walker, Eloise Busby, 2013, Development of an in-house plasmid control for Cauliflower Mosaic Virus (CaMV) for the detection of genetically modified (GM) Chinese rice lines, J. Assoc. Public Analysts (JAPA), 41, 45- 52.