Abstract: Event-specific detection constitutes a fundamental methodology in the identification and regulatory oversight of genetically modified organisms（GMOs）,providing critical support for the precise quantification of transgenic crops. This study focused on CC-2, a transgenic maize event developed in China, with the objective of establishing a highly specific and sensitive quantitative detection assay using droplet digital PCR (ddPCR). Primers and probes were designed based on the specific insertion sequence of the CC-2 event. Following systematic optimization of amplification conditions, a duplex ddPCR system was successfully developed, enabling the simultaneous detection of the endogenous gene and the CC-2 event-specific sequence. The verification results demonstrate that this method exhibited no cross-amplification in various non-target GM events, confirming the high specificity of the assay; a linear response was achieved covering a range of 20 to 20,000 copies/reaction for CC-2 DNA, with the limits of detection (LOD) and quantification (LOQ) reaching 10 and 20 copies, respectively. In blind testing, the method demonstrated high repeatability and accuracy across samples containing varying concentrations of the event, meeting the national and international standards for quantitative GMO analysis. The ddPCR method developed in this study provides a robust technical foundation for both the commercial propagation and regulatory monitoring of transgenic maize CC-2.

Key words: Transgenic maize, CC-2, Droplet digital PCR, Quantitative detection