## 5 Conclusions  
In this study, the SBSE method and GC-O/MS technique were used to evaluate the aroma components of Lingtou Dancong oolong tea made from plants grown at different altitudes. A total of 59 common aroma compounds were identified and quantified. The PCA and OPLS-DA confirmed differences in the aroma quality of tea from different altitudes. The categories of aroma compounds in teas from different altitudes were the same, but the contents and proportions were different. These differences, together with the thresholds of each aroma compound, affected the final aroma profile of the various teas. Using OAV (the information of threshold was referred to the literatures [5; 6; 12; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41]) and FD analyses, the eight odor compounds making the largest contributions to aroma were screened, and most of them had honey and floral fragrances. Among them, hotrienol, (\(E\))-\(\beta\)-damascenone, and _cis_-citral were the most noteworthy contributors to aroma (Figure 4B). All of them have a honey fragrance, and together they may confer the honey fragrance of Lingtou Dancong oolong tea. Their presence and contents may be related to the variety and/or the subsequent processing methods, but further analyses are required to explore these ideas in more detail. The contents of linalool (a key component of floral fragrance) and hotrienol (a key component of honey fragrance) varied with altitude. Its higher content at higher altitude was consistent with higher contents of its precursor, GPP, as well as higher transcript levels of _CsLISs_ in the fresh leaves (Figure 6). The results of this study shed light on the aroma compounds that contribute to the fragrance of Lingtou Dancong oolong tea. Our results will be useful for devising strategies to control the contents of various aroma compounds in tea during cultivation and processing. Figure 6: Aroma characteristics of Lingtou Dancong oolong tea and the effect of altitude on it. GPP, geranyl diphosphate; _LIS_, _linalool synthase_. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/metabo12111063/s1](https://www.mdpi.com/article/10.3390/metabo12111063/s1)]([https://www.mdpi.com/article/10.3390/metabo12111063/s1](https://www.mdpi.com/article/10.3390/metabo12111063/s1)), Figure S1: OPLS-DA model validation; Figure S2: Expression level of _CsLISs_ in fresh leaves and wounded leaves of Lingtou Dancong grown at different altitudes; Table S1: Threshold information; Table S2: The primers used for quantitative real time PCR (qRT-PCR) in the study; Table S3: Detailed information of Lingtou Dancong tea product at high altitude; Table S4: Detailed information of Lingtou Dancong tea product at medium altitude; Table S5: Detailed information of Lingtou Dancong tea product at low altitude. **Author Contributions:** Data curation, M.W. and L.Z. ; methodology, M.W. ; writing original draft, M.W. and J.L. ; investigation, M.W., J.L., C.L., J.Q., J.Y., X.Z. and Y.J. ; resources, J.L., X.L. and J.T. ; formal analysis, J.L., C.L., J.Q., J.Y., X.Z. and Y.J. ; conceived and designed, supporting the project, [PERSON] and L.Z. ; revising the manuscript, M.W. and L.Z. All authors have read and agreed to the published version of the manuscript.