The development of transgenic events can be limited by many factors. These include expression levels, insert stability and inheritance, and the identification of simple insertion events. All of the factors can be related to the copy number of the transgene. Traditionally, copy number has been determined by laborious blotting techniques. We have developed an alternative approach that utilizes the fluorogenic 5' nuclease (TaqMan) assay to quantitatively determine transgene copy level in plants. Using this assay, hundreds of samples can be analyzed per day in contrast to the low throughput encountered with traditional methods. To develop the TaqMan copy number assay, we chose to utilize our highly efficient Agrobacterium-mediated transformation system of maize. This transformation procedure generates predominantly low copy number insertion events, which simplified assay development. We have also successful applied this assay to other crops and transformation systems.

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International safety assessments and independent publications conclude that stacking genetically modified (GM) traits (events) through conventional breeding poses no greater risk to food or feed safety than stacking multiple non-GM traits by conventional breeding. Stacked trait products are not substantially different from their conventional comparator or their GM parent plants. Additional safety assessment of a stacked trait product produced by conventional breeding should not be required unless there is a plausible and testable hypothesis for interaction of the traits. However, the different approaches employed for the regulation of stacked trait products between countries results in asynchronous approvals, increasing the potential for trade flow disruptions, and adds to the regulatory burden for product developers. Considering their proven safety and benefit over the past 20+ years, regulatory authorities in some countries do not regulate stacked trait products, while others have simplified the approval process based on experience and sound science, reducing or eliminating the need for additional regulatory oversight. Countries that choose to regulate stacked trait products should consider integrating the more than 20 years of safety assessment experience, history of safe use, and global regulatory experience, in their approach to reduce redundancy, simplify regulations, and minimize the likelihood for trade disruption. doi: 10.21423/jrs-v09i1goodwin