Provenance of Mytilus food products in Europe using SNP genetic markers

Mussels of the Mytilus genus or blue mussels are cultured extensively worldwide. According to FAO statistics in 2019, the main cultured species in order of annual production are M. chilensis, M. edulis and M. galloprovincialis. Due to their morphological similarity, blue mussels may be incorrectly assigned to the species leading to the occurrence of inconsistencies in the food labeling. Molecular markers in mono-locus or multi-locus approaches have often been used for species identification.This paper aimed to assess the information about the species and geographical origin labelled on mussel products available in European stores and markets in 2011-2015 using a multi-locus approach based on Single Nucleotide Polymorphisms (SNPs). A total of 491 Mytilus spp. individuals from 21 food samples purchased mainly in Italy, Spain, Poland and Germany, were genotyped using a 54 SNP panel. Most of the declared in-formation on the labels of food products was consistent with the results obtained with genetic tools (85%). However in-complete information, such as missing commercial designation, scientific name, or geographic origin was found in 11 samples. Also, incorrect information about the species origin of a few samples of fresh mussels imported from other countries to the Mediterranean was observed in fishmongers' shops. The results consistently revealed a division of the European food samples into two species: M. edulis and M. galloprovincialis (Atlantic and Mediterranean forms). The presence of M. trossulus in the food samples was not observed. Our results confirm that traditionally used single molecular diagnostic markers can provide only preliminary information on the taxonomic status of Northern hemisphere mussels included in food products. A multi-locus approach based on a set of multiple SNPs is needed for correct label assessment. The results demonstrate that a reduced panel of 34 SNP loci can be widely used to confirm the geographical origin and the identity of Mytilus taxa in food samples, verify data on food labels, and monitor the mussel trade in Europe.

Automated summary

This study assessed the species and geographical origin information labeled on mussel products available in European stores and markets using a genetic approach. The results showed that most of the information on the food labels was consistent with the genetic tools, but incomplete and incorrect information was also found. The study confirmed that a multi-locus approach based on multiple SNPs is needed for accurate species identification, and a reduced panel of 34 SNP loci can be widely used for this purpose.