Extraction of DNA from choline chloride feed additive (CC) and from derived pre-mixes (PMCC) and screening of CC and PMCC for (a) presence of rice and (b) presence of BT63

Choline Chloride 60% (CC) is a feed additive that is imported in significant quantities from China. In a number of cases GM rice, harbouring the event Bt63, has been found in imported CC batches but not in derived pre-mixes. The Member States were asked to provide positive CC samples and derived pre-mixes to the EU-RL GMFF in order to allow the EU-RL GMFF establishing practical approaches to DNA extraction and the subsequent testing for presence of (a) rice and (b) the Bt63 rice event. This technical note has been derived based on data provided from National Reference Laboratories (NRLs) and experience made by the EU-RL GMFF when re-testing eleven feed additive samples and eight pre-mixes samples (as of 16 May 2014). It was found that the extraction of DNA from the feed additive Choline Chloride (CC) does not normally pose specific problems. It can be carried out following the available protocols or using available standard DNA extraction kits. The extraction of DNA from derived pre-mixes (PMCC) is posing problems because of observed strong inhibition and the presence of DNA from additional sources than those present in the CC. The EU-RL GMFF has tried a number of protocols and extraction kits on PMCC samples. On this basis it is concluded that it is advisable to carefully purify the DNA, to verify the possible presence of inhibition effects and eventually to try to reduce any inhibition observed. Concerning testing the extracted DNA for rice and Bt63 rice event presence, this does not pose a problem in case of the CC while for PMCC rice was not anymore detectable or was detected in trace amounts. A possible explanation could be that much of the extracted DNA is from other plants than rice and hence the concentration of rice DNA is below the LOD of the rice-taxon specific method. The EU-RL GMFF has analysed the available rice (taxon-) specific methods by means of bioinformatics and (partly) in the laboratory and concludes that they all should be suitable for specifically and reliably detecting rice from the Oryza sativa species. The re-testing by the EU-RL GMFF of CC and PMCC samples has in all cases, except one, confirmed the results of the initial tests. EURL