Species identification of culinary spices with two-locus DNA barcoding

Culinary spices are widely used as both condiments and food. However, some cheaper species with similar morphological characteristics are utilized as substitutes or additives, causing issues with quality control and product safety. This study aimed to develop a DNA barcoding method for the species identification of culinary spices. We evaluated the ability of five barcodes (ITS2, rbcL, trnL (UAA), trnL (P6 Loop), and psbA-trnH) to detect 19 culinary spices. The reliability of barcodes for distinguishing species was assessed using PCR amplification and sequencing, genetic distance, barcoding gap, neighbor-joining phylogenetic tree, and BLAST analyses. When the five barcodes were used independently, the 19 types of culinary spices and three common crop-based adulterants could not be definitively identified simultaneously. The ITS2 region, followed by the psbA-trnH, trnL (UAA), and rbcL regions, had intra- (0.0099) and inter- (0.8955) specific divergences, a barcoding gap, and an 86.7% species resolution rate. The combination of ITS2 and psbA-trnH barcodes improved the species identification ability (95.5%). Except for the Cambodian cardamom, all the tested culinary spices were successfully identified using the ITS2 + psbA-trnH barcode group. Utilizing the ITS2 + psbA-trnH barcode, we tested the authenticity of 30 commercial products. The recovery rate of DNA barcodes from culinary spice products was 100.0%, with 93.3% of the tested products being authentic, and 6.7% indicating adulteration with Oryza sativa. Our findings provide an effective tool for culinary spice identification that is easy, accurate, and quick. This method can be used to standardize labels on commercial culinary spices.

Automated summary

This study aimed to develop a DNA barcoding method for the species identification of culinary spices. Five barcodes were evaluated to detect 19 culinary spices, but they could not definitively identify all the species. The combination of ITS2 and psbA-trnH barcodes improved the identification ability, successfully identifying all tested spices except for Cambodian cardamom. The method can be used to standardize labels on commercial culinary spices.