Impact of Roundup Ready® Canola on Plant Pathogen and Its Suitability as Animal Feed: A case study in Canada

Abstract

The steady increase in world production of genetically modified (GM) or transgenic crops since their introduction in the 1990s has caused some concerns, regarding the bio-safety on persistence and stability of recombinant DNA from GM crops. A field experiment was established in 2000 at the Agriculture and Agri-Food Canada Lethbridge Research Centre to investigate the long-term environmental impacts of some GM crops approved for production in Canada, including GM canola, corn and potatoes. One of the objectives of this study was to investigate horizontal gene transfer (HGT) from Roundup Ready®(RR ) canola (Brassica napus event RT73) to Sclerotinia sclerotiorum , causal agent of stem blight of canola . The investigations focused on the cp4 5-enolPyrulylshikimate-3 phosphate synthase (cP4 EPSPS gene, which endows RR canola with herbicide tolerance towards glyphosate. PCR and Southern hybridization were used to test sclerotia of S. sclerotiorum produced in diseased stems of RR canola and conventional canola, which were collected from the field in 2004 and 2005, for the presence of the 1363 bp cP4 EPSP transgene and four of its fiagments; three of which were construct-specific and one that was gene- specific . Results of PCR showed that cP4 EPSPS was present in diseased RR canola stems but was absent in sclerotia of S. sclerotiorum formed inside the same stems. These results were further confirmed by Southern blotting and hybridization. The study concludes that there IS no evidence for recombinant DNA transfer of cP4 ERSPS or any of its constituent fragments from RR canola to the pathogen S. sclerotiorum. From our studies with animals we found that feed-ingested DNA fragments do survive the terminal Gastrointestinal (GI) tract, but recombinant DNA in the gut is processed similar to any other endogenous feed-ingested genetic material. Plant DNA from GM feed degrades very rapidly upon its release into the rumen fluid. We did not detect any cP4 EPSPS fragments in the microbial DNA fraction of in vitro ruminal cultures, suggesting that bacterial transformation did not occur. Based on our investigations it was clear that uptake of transgenic DNA fragments by ruminal bacteria 15 precluded or time-limited by rapid degradation of plant DNA upon plant cell lysis. Thus use of GM canola as animal feed is safe and should be encouraged based on the scientific findings.