Helen M. Booker and Eric G. Lamb
University of Saskatchewan, Canada
Detection and quantification of the prevalence of genetically modified (GM) organism contamination in seed exports is a critical element of regulatory compliance. While the procedures to reliably detect high levels of GM contamination are well understood, no comparable statistical approaches are available for the quantification of levels of GM prevalence below the established detection rate of standard tests. Presented is a simple statistical approach based on simulation modeling for the quantification of low levels of GM contamination. The approach can be modified to match any sampling regime and can account for rates of false positive and negative assay results. The application of this method is demonstrated using the low level of contamination in Canadian commercial flax stocks by the GM flax variety “Triffid.” We show that rates of GM contamination in commercial flax stocks ranged between one (1) GM seed per million and one (1) seed per hundred thousand. A simulation model was used to determine whether the observed rates of positive tests are within the range expected from false positive rates of the test. We showed that for the majority of categories of grain or seed, the very low level of GM prevalence still remains outside that which is to be expected based on false positives returned or by chance alone. These results indicate a pervasive low-level presence of GM construct in the Canadian commercial flax system.
Key words: CDC Triffid, flax (Linum usitatissimum), GMO, seed purity analysis, seed testing, statistical methods, transgenic seeds.