Optimization of geographical traceability models for tobacco: an investigation into the effects of region, harvest year, and variety on stable isotope and multi-elemental profiling

Geographical traceability of tobacco, a crop of substantial economic importance and industrial value, is essential for authenticating origin, ensuring quality, and supporting regulatory compliance. The fingerprint signatures of stable isotopes and mineral elements in tobacco are to a great extent the interannual climate variability, agricultural practices (e.g., fertilization and irrigation), and varietal differences, thereby increasing the complexity and uncertainty in geographical origin identification. To date, tobacco research has been largely restricted to geographical differences, while the influences of inter-year and cultivar differences have not been systematically investigated. In total, 523 tobacco samples were collected from three distinct production regions across China between 2020 and 2022, encompassing three varieties specifically from Yunnan Province. Stable isotope signatures (δ 13 C, δ 15 N, δ 2 H) and mineral element profiles differed significantly among regions, and regional variation exceeded inter-year variation. In contrast, δ 2 H values and the concentrations of K, Ni, Ga, Sb, Ba, Y, Sm, Dy, Er, Pb, and Sr did not differ significantly across cultivars. We identified ten key variables (Sr, Pr, Na, Ga, Sm, Sn, Ba, Li, Dy and Cs) that reliably discriminate tobacco origins, independent of cultivar or year. Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) models achieved prediction accuracies of 98.6%–99.4% for the training set and 85.8%–93.6% for the test set. These findings demonstrate that origin, harvest year, and variety significantly impact the stable-isotope and elemental composition of tobacco, and that regional differences exceed the inter-year differences. This indicates that the verification method used in this study offers a powerful tool for verifying authenticity-of-origin labels on tobacco products.