Rapid and low-cost identification of common sole (Solea solea) in the field using a fast DNA isolation protocol and loop-mediated isothermal amplification (LAMP)

Seafood is a major food source worldwide, but it is prone to fraudulent activities such as species substitution. DNA barcoding is currently the most used tool to identify processed seafood, but remains expensive, time-consuming, and requires heavy and expensive lab equipment and expert knowledge. Here we compared the Nucleospin® Food kit with a dipstick-based, a paramagnetic bead-based, and an alkaline-based DNA extraction method on tissue of common sole (Solea solea). The alkaline-based method was the most reliable and cheapest, with the lowest hands-on time. A S. solea-specific loop-mediated isothermal amplification (LAMP) assay was designed using the cytochrome b (cytb) gene with a limit of detection (LOD) of 0.1 ng. The alkaline-based DNA extraction and LAMP was validated using ten sole fillets under different preservation conditions (fresh, frozen, and ethanol stored), and ten previously identified sole dishes. A combination of the alkaline-based DNA extraction and the LAMP assay detects common sole in seafood products within an hour in the field, and at a cost of less than half a euro. The method developed in this study is applicable in large-scale audits of sole products. Similar methods may emerge for other seafood species allowing seafood fraud studies in labs short on resources.