New laboratory procedure lets scientists monitor for up to four GM events with a single test

Genetically modified (GM) crops have become increasingly common since they were first commercialized in the 1990s. At the same time, consumers around the world have become more concerned with what is in their food. As an exporting country, Canada needs effective methods for detecting and monitoring GM events in important crops such as soybeans and canola as required.

A real-time polymerase chain reaction (PCR) assay is a laboratory procedure widely used to detect and quantify individual GM events. To use a real-time PCR assay to monitor for a particular GM event, a certified reference sample must be used to develop a suitable standard curve for that event. A standard curve is a graph used to measure different concentrations of a GM event. The standard curve is then used to calculate the amount of that GM event present in the test sample. Digital PCR (dPCR) can be used to measure the presence of a GM event in a sample without the use of a reference sample or standard curve. In general, dPCR is performed to detect one GM event at a time. To monitor for more than one GM event in the same sample, the test is performed multiple times.

We decided to investigate whether we could accurately detect and quantify two, three, and four GM events at the same time. Using the QX200 Droplet Digital PCR (ddPCR) system, we attempted to detect and quantify multiple GM events in canola and soybean at three different concentrations: 0.1%, 1%, and 5%.

We were able to obtain successful multiplex ddPCR results at each concentration tested. With optimization of the assays, we were able to detect and quantify four GM events with just one test. The assays we developed in this study can also be used to detect and quantify other GM events more efficiently, reducing the time and resources required for monitoring.