It's what's inside that counts: DNA-barcoding of porcini (Boletus sp., Basidiomycota) commercial products reveals product mislabelling

Abstract

In the edible mushroom market, porcini (Boletus edulis Bull., and related species) are a very economically valuable product, with 20–100 tons of these mushrooms being sold each year worldwide. However, products sold as “Boletus edulis” are often a mix of different species, some of them of less value than “Boletus edulis” but sold at the same price. DNA-Barcoding is a powerful tool that can help uncover this kind of fraud in a rapid and accurate way.In this study, we combine visual inspection with DNA barcoding and phylogenetic analyses to assess the quality and provide accurate identifications of nine different dehydrated porcini commercial products destined for human consumption. DNA was extracted and the internal transcribed spacer (ITS) region, the fungal DNA barcode, was amplified and sequenced from a total of 108 samples (twelve per product) and five reference Boletus sp. sporocarps from the UVigo-FUNGI fungarium. Five products contained mushrooms in various states of decay, worm infestation and pathogen contamination, which would not be suitable for sale as fresh sporocarps following the current legislation. B. edulis was only found in three of the nine products, being B. reticulatus the most abundant species. Two Asian species of porcini, B. bainiugan and B. meiweiniuganjun, were also found in one product during the phylogenetic analyses. Three non-porcini Boletaceae were found, but only one (Imleria badia) could be identified to species level. Lastly, four samples were identified as the fungal pathogen Hypomyces chlorinigenus, indicating decay of the sporocarps.Overall, our results show that DNA-barcoding is a powerful tool for the identification of mislabelling and fraud in porcini products in a rapid and accurate way.