Unique region produces special tea: Metabolomic basis of the influence of production region on the quality of Wuyi Rock Tea

Wuyi rock tea is one of the best oolong tea in China, and Yanyun is the key quality component of Wuyi rock tea. It has been well known that Yanyun is closely influenced by production region, but its underlying mechanism is still unclear. In this study, 112 tea plantations were randomly selected from three main tea production regions in Wuyi mountain area, including Zhengyan, Banyan and Zhou tea region. In total, 1120 fresh tea leaf samples and 224 soil samples were collected and analyzed. The phenotype of Yanyun was identified based on the metabolomic analysis through ultra-high performance liquid chromatography-four-stage rod-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The results demonstrated that the metabolites significantly varied among the tea samples from different regions. The correct rate was 94.94% in classifying the production regions using the 1058 detected metabolites, indicating that the metabolite phenotypes analyzed by UPLC-Q-TOF/MS could be used for the discrimination of Yanyun in Wuyi rock tea. Constrained principal component analysis (CPCoA) showed that the production region significantly influenced the tea metabolites, which accounted for 32.9% of the total variations; while analysis of similarities (ANOSIM) demonstrated that the metabolites of tea samples from different plantations within the same region were highly similar (R=0.638>0). CPCoA also significantly separated the soil fertility (i.e., pH, organic matter, alkali-hydrolyzed nitrogen, available phosphorus and available potassium content) by the production region, which fit well with the separation pattern of tea metabolites. These results imply that soil fertility might directly influence Yanyun. In addition, each soil fertility index was significantly associated with particular quality factors, including theanine, caffeine, catechin and five polyphenol monomers (ECG, EGCG, EGC, GC, GCG) as quantified by high performance liquid chromatography (HPLC), which further demonstrated that soil fertility influenced tea quality, and thereby Yanyun. This study provides a scientific basis for elucidating the mechanism underlying production region and Yanyun, and offers a point of reference for best nutrient management in tea plantations for producing high-quality tea.