UK researchers develop control material to improve GM rice testing

A team of researchers from the UK’s Government Chemist Programme, in LGC, have developed a new control material to help laboratories identify false positives when monitoring imports for genetically modified (GM) rice in food products originating from China.

The report on the control material has been published in a paper in the Journal of the Association of Public Analysts (JAPA).

Genetically modified foods are those produced using genetically modified organisms (GMOs) and specifically genetically modified crops.

GMOs have had specific changes implemented into their DNA by genetic engineering techniques where an organism is treated to radiation or chemicals to create a non-specific but stable change.

Under European law, laboratory tests are required for all imported rice products imported from China.

There are no GM rice varieties approved for use in the EU; however, there are reportedly more than 25 varieties that may be a source of contamination.

A process is in place to identify the safety of GM food in the EU and all the rice consignments imported into the EU from China are screened for the presence of specific molecular markers that are associated with genetic modification.

If GMOs are detected, the consignments are destroyed or re-dispatched to their country of origin.

The P-35S promoter sequence, which is derived from Cauliflower Mosaic Virus (CaMV), is one of the genetic elements screened in order to infer the presence of GM rice.

The sequence is also found in naturally occurring CaMV, which can can infect plants such as cauliflower and turnip and affect plant growth, but poses no risk to humans.

As a result, the presence of the P-35S promoter sequence means that a consignment is contaminated with unauthorised GM rice, and laboratories must ensure that it is not a false positive from naturally occurring CaMV.

According to researchers, to date, there has not been a straightforward way of verifying that the tests for the natural virus worked properly in the lab, but the new control material can help labs identify false positives when monitoring imports for genetically modified (GM) rice.

For the study, the researchers synthesised a specific DNA sequence from CaMV and inserted it into a standard plasmid to provide a suitable control, and then tested using a validated and EU approved PCR assay.

The team was successful in amplifying the DNA target in the CaMV plasmid control, while detecting approximately four copies of the plasmid target.

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."

Burns added: "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."

The study, which is aimed at developing a suitable plasmid control DNA for CaMV, was funded by the National Measurement Office.

LGC, headquartered in Teddington, London, is a science-based company and is involved in the laboratory services, measurement standards, reference materials and proficiency testing marketplaces.

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Image: The new method involves synthesising a specific DNA sequence from CaMV and inserting it into a standard plasmid to provide a suitable control for rice testing. Photo: Courtesy of Kate Hayter.