Development of a Duplex Digital PCR Method to Quantify Five Genetically Modified Soybean Events

The presence of genetically modified organisms (GMOs) in food and feed products is regulated in many countries. Various countries have issued labeling threshold levels to supervise GMO commercialization, and efficient detection methods to quantify GMO contents are critical to meet labeling regulations. The aim of this study was to develop event-specific methods to measure the event-specific/lectin gene (Le1) copy number ratio in soybean using droplet digital PCR (ddPCR), which is a recently developed technology that offers high accuracy. Duplex ddPCR methods were developed and optimized using a central composite design for the five most widely authorized GM soybean events, in which the target gene was labeled with one fluorescent reporter and the endogenous gene with another. The methods produced specific results, and the performance complied with international GMO labeling regulations. Further, the duplex ddPCR methods are compatible with chip-based digital PCR platforms and original real-time PCR, but allow higher throughput and are more sensitive in identification and quantification of these five widely authorized genetically modified soybean events.