Development of an in-house Plasmid Control for Cauliflower Mosaic Virus (CaMV) for the Detection of Genetically Modified (GM) Chinese Rice Lines

Malcolm Burns(a,b), Gavin Nixon(a), Michael Walker(a), Eloise Busby(a)
a) LGC, Queens Road, Teddington, Middlesex, TW11 0LY, UK
b) To whom correspondence should be addressed. E-mail:, Telephone: (+44) (0)208 943 7000,
   Fax: (+44) (0)208 943 2767


On 12th January 2012 Commission Implementing Decision 2011/884/EU was adopted which describes emergency measures regarding unauthorised genetically modified rice in rice products originating from China. All rice consignments imported into the EU from China are subject to testing for the presence of molecular markers and elements often associated with genetic modification. At present there are no genetically modified (GM) rice varieties approved for use in the European Union, and upon detection consignments containing these genetic elements 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. Guidance in support of the Commission Implementing Decision 2011/884/EU provided by the European Union Reference Laboratory (EURL) for GMO’s in food and feed advocates that appropriate follow-on tests be conducted to ensure that the detection of P-35S is not a false positive due to the natural occurrence of CaMV present with the test sample. However, the EURL Guidance does not provide further instruction on what control material can be used to facilitate such a test, creating an analytical void in the correct application of such a test for false positives.

The present study aimed at developing a suitable plasmid control DNA for CaMV. This was analysed alongside appropriate samples that contained P-35S only, using a validated and EU approved real-time PCR assay that could be used as a follow on test for the detection of Chinese GM rice varieties. The assay 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. All other sample templates that contained just P-35S produced no detectable amplification. This illustrates the use of the CaMV plasmid DNA as an appropriate control material in conjunction with EU-approved tests for the detection of false positives arising from the application of the P-35S test for the detection of Chinese GM rice varieties in support of the relevant legislation.


GMOs, Chinese GM rice, Plasmid Control, CaMV

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