Development of event-specific quantitation method for GA21 maize [Zea mays], which is a GM event without CaMV35S promoter

A real-time PCR detection method was developed for event-specific quantitation of Roundup Readysup(R) maize, GA21. The developed PCR method was designed to amplify an artificial junction site between the native maize genome DNA and the recombinant DNA of GA21 maize, which provides only one target sequence per haploid of GA21 genome. Thus, the amplification efficiency of the event-specific target for GA21 became closely similar to the amplification of SSIIb, and the conversion factor (Cf) for the quantitation method was similar to the theoretical value. The developed method demonstrated better performance than the existing construct-specific method that has been used as a Japanese official method. The developed method can easily be combined with the real-time PCR targeting of the CaMV35S promoter, and the multiplexed method should be an effective screening method for GM maize.