The detection of Atlantic cod (Gadus morhua) using loop mediated isothermal amplification in conjunction with a simplified DNA extraction process

Atlantic cod (Gadus morhua) is a commercially important species of white fish, and one of three species legally identifiable as cod in the UK. Mislabelling of G. morhua does occur, as does the substitution of G. morhua for less expensive species. Sensitive molecular tests based on PCR have been developed for this species, but they have limitations, including the need for expensive thermal cycling equipment, and complex DNA extraction procedures. A loop mediated isothermal amplification (LAMP) assay was designed for the G. morhua cytochrome b gene, which was capable of detecting 0.1% w/w G. morhua in a homogenised raw fish mix. The LAMP assay was also able to detect G. morhua DNA when a rapid sample preparation was used, involving heating 100 mg of fish in a 1 ml aliquot of water and testing the supernatant, showing a higher tolerance of amplification inhibitors than a PCR assay. The LAMP assay did not generate a positive result when challenged with a range of non-target species, including Gadus macrocephalus, and Gadus chalcogrammus, indicating a high level of specificity. Direct detection of a positive reaction using propidium iodide was also demonstrated.