Roundup Ready® soybean event-specific real-time quantitative PCR assay and estimation of the practical detection and quantification limits in GMO analyses

An event-specific real-time PCR method for detection and quantification of genetically modified Roundup Ready soybean with TaqMan chemistry on the LightCycler, targeting the nopaline synthase terminator (3 ') junction between recombinant and host plant DNA is described. We distinguish between three types of detection and quantification limits: the absolute limits (referring to the initial number of template copies in the PCR), the relative limits (referring to the relative percentage of initial template copies of the recombinant sequence to copies of the haploid soybean genome that is detected), and the practical limits (referring to what is applicable in the PCR with the DNA that is being analysed). The absolute detection limit was determined to be a single initial template copy, while the absolute quantification limit was determined to be approximately 30 initial template copies. We discuss the relative and practical limits, and provide guidelines to estimating the practical limits.