Authentication of Chinese prickly ash by ITS2 sequencing and the influence of environmental factors on pericarp quality traits

Chinese prickly ash is widely cultivated as a medicinal and edible plant. The pericarps are extensively used because of their unique flavour and various biological compounds, such as volatile oils, flavonoids, polyphenols, and acid amide. Due to higher financial gain, incongruence in the vernacular names, and similarity in morphology among some species or cultivars, adulteration and associated fraudulent practices may occur in trading these substances. The location, soil conditions, and management actions influence the growth of these plants. Thus, authentication and quality difference evaluations of pericarps from different cultivation regions of Chinese prickly ash are required. First, the ITS2 sequence, a DNA barcode with the advantages of universality, small intraspecific variation, high interspecific divergence, and a small fragment length, was applied to authenticate Chinese prickly ash pericarps collected from 72 plantations. Then, the main quality traits (colour, thousand pericarp weight, numb taste intensity, and volatile oil content) of Chinese prickly ash pericarps among different species were compared. Moreover, the influence of environmental factors on these quality traits of Chinese prickly ash was reported. The results identified confounding in pericarp species in the main cultivation regions (more than two species with red colour). The colour, size, volatile oil content, and ITS2 sequence of pericarps were significantly different among species. Fifty-eight polymorphic sites and two indel sites were identified in the alignment that could differentiate these species using ITS2. In addition, colour distinguished Zanthoxylum armatum from all other species, and size distinguished Z. bungeanum from Z. piperitum (since they both were red), but these two traits which authenticate Chinese prickly ash could have errors due to the similarity of the size and colour among the Chinese prickly ash species. The main quality trait differences and these traits influence among different species were significant, especially between Z. armatum and Z. bungeanum. Latitude of the cultivation region was a key influence factor on the main quality traits of both Z. bungeanum and Z. armatum. In addition, soil pH had a positive effect on the main quality traits of Z. bungeanum, and altitude had a positive effect on taste intensity and a negative effect on the b* of pericarps. Overall, the main quality traits of Chinese prickly ash combined with the molecular method provided useful information to authenticate pericarps of Chinese prickly ash.