Cytochrome oxidase-I sequence based studies of commercially available Pangasius hypophthalmus in Italy

Pangasius hypophthalmus is one of the fish consumed in the Italian diet. It is farmed and imported from Mekong delta region of Vietnam. Among several types of Pangasius, Tra (Pangasius hypophthalmus) is permitted for sales by the European Union. Since these fish species are often allegedly substituted with other morphologically similar fish due to commercial benefits, authentication of the products in the international markets become often necessary to prevent fraud and safety issues. In addition, this fish is imported as fillets without skin and bone, thus leaving the consumer's at the risk of buying a substandard nutritional food. In this article we present the molecular approach we developed to identify Pangasius hypophthalmus from other closely related species based on cytochrome oxidase-I (COI) mitochondrial barcoding gene and further described the variants in the studied population genetic of this species. Fifty-one samples of Pangasius hypophthalmus fillets labelled as Pangasio were obtained from various markets around Milan and their COI mitochondrial barcoding gene was sequenced and studied in our bioinformatics pipeline. All samples were successfully amplified and Basic Local Alignment Search Tool results of the amplified region confirmed that all sequences analysed belonged to Pangasius hypophthalmus. Based on the variations in their barcoding region single nucleotide polymorphisms were identified and delineative statistics was calculated on the sequences. Although Pangasius hypophthalmus is considered as a monophyly, seven polymorphisms were identified. The neighbour-joining tree and the Median-joining network of haplotypes showed for all the identified haplotypes a unique cluster, with the exception of one sample.