Abstract:ITS2, matK, and PsbA-trnH molecular markers were used to identify 13 common aromatic plants, including Ocimum basilicum and its relatives, Ocimum americanum, Ocimum gratissimum, Ocimum tenuiflorum and Origanum vulgare, Mentha canadensis, Mentha spicata, Elsholtzia ciliata, Agastache rugosa, Nepeta cataria, Melissa officinalis, Rosmarinus officinalis, and Thymus mongolicus, to provide a more scientific method for rapid and accurate identification of medicinal and edible aromatic plants. The ITS2, matK, and PsbA-trnH sequences of each species were downloaded from GenBank. The sequence alignment, genetic distance calculation, and neighbor-joining (NJ) phylogenetic tree construction were performed using MEGA7.0 software. The parallel neighbor-joining (PNJ) evolutionary tree was also constructed in combination with the secondary structure of ITS2. The results showed that the maximum intraspecific genetic distance of ITS2 was 0, and the minimum interspecific genetic distance was 0.070. The maximum intraspecific genetic distance of matK was 0.000, and the minimum intermediate genetic distance was 0.002. The maximum intraspecific genetic distance of the PsbA-trnH sequence was 0.000, the same as the minimum interspecific genetic distance. Simultaneously, according to the results of the NJ phylogenetic tree, ITS2 and matK barcodes can distinguish all species, with each species forming a distinct clade, clearly separable from other species. PsbA-trnH could distinguish plants at the genus level but failed to distinguish Ocimum basilicum from the closely related species Ocimum americanum. Therefore, the differential effect of the three molecular markers was as follows: ITS2 was the best, matK was the second, and PsbA-trnH was weak. Thus, ITS2 was suggested for the identification of 13 medicinal and edible spice plants in this study, providing a scientific basis for the traceability of spice origins and ensuring safety in food and pharmaceutical applications.
