Abstract: Objective: To develop a real-time polymerase chain reaction (real-time PCR) method for the detection of Lepidocybium flavobrunneum- and Ruvettus pretiosus-derived components. Methods: The mitochondrial cytochrome C oxidase subunit I (COI) gene sequences of 18 cod species including L. flavobrunneum, R. pretiosus and Gadus morhua and other species commonly used as adulterants were aligned with one another, and L. flavobrunneum- and R. pretiosus-specific primers and probes were designed and used to establish a real-time PCR method for the detection of the two fishes. The specificity, absolute sensitivity and relative sensitivity of the PCR method were assessed. In order to evaluate the practicability, 50 commercial products labeled as cod were tested by this method. Results: This method showed high specificity, with absolute sensitivity of 0.002 and 0.000 2 ng/μL for L. flavobrunneum and R. pretiosus, respectively, and relative sensitivity of 0.01% for both so that it could be applied to detect actual samples. The two fishes were separately detected in one of the 50 samples, consistent with sequence alignment. Conclusion: The proposed method in this study displayed good specificity and sensitivity towards the detection of L. flavobrunneum- and R. pretiosus-derived components, and could provide technical support for the detection of adulterated aquatic products to protect consumer rights.

Key words: Lepidocybium flavobrunneum; Ruvettus pretiosus; oilfish; real-time polymerase chain reaction; COI gene