Rainbow trout (Oncorhynchus mykiss) identification in processed fish products using loop‐mediated isothermal amplification and polymerase chain reaction assays

Abstract BACKGROUND Financial loss and health risk caused by the substitution of rainbow trout for other salmonid species have become a common issue around the world. The situation could be further exacerbated in China by the ‘abused’ common name of San Wen Yu (the corresponding Chinese ideogram 三文鱼 ) for salmonids, considering the absence of a standardized naming system for seafood species. To prevent such episodes, the present study aimed to develop novel loop‐mediated isothermal amplification (LAMP) and polymerase chain reaction (PCR) assays targeting the mitochondrial cytochrome b gene for rapid identification of rainbow trout in processed fish products. RESULTS Rainbow trout‐specific primers (LAMP and PCR) were designed, and the specificity against 23 different fish species was confirmed. The minimum amount of detectable DNA for LAMP assay reached 500 pg, up to 10‐fold less than for PCR assay. In addition to agarose gel electrophoresis, naked‐eye inspection of the LAMP‐positive samples using SYBR Green I under daylight or ultraviolet light was also validated. Finally, commercial San Wen Yu products made from rainbow trout could be accurately identified using the newly developed LAMP and PCR assays, further cross‐confirmed by mini DNA barcoding and neighbor‐joining dendrograms. CONCLUSIONS The LAMP and PCR assays established in the study allow a fast and accurate identification of rainbow trout in processed fish products. © 2020 Society of Chemical Industry