Effects of Different Cultivation Measures on the Plant Type Tier Interaction Ratio and Sensory Quality of Yunyan 87 in High-altitude Tobacco-growing Areas

Purpose This paper aimed to investigate the plant type tier interaction ratio (TIR) ratios at different growth stages of Yunyan 87 under various cultivation measures in the high-altitude tobacco-growing area of Yanyuan, Sichuan, and its effects on the sensory quality of flue-cured tobacco leaves, so as to provide a theoretical basis for targeted cultivation and quality improvement of high-quality tobacco leaves in high-altitude tobacco-growing areas.

Methods A three-factor three-level orthogonal experimental design was employed, and three factors were nitrogen application rate (90, 105, 120 kg/hm²), planting density (12 810, 13 980, 15 375 plants/hm²), and number of retained leaves (18, 20, 22 leaves). Plant type parameters of Yunyan 87 were measured at budding stage, buttoning stage, and harvest stage, respectively. Combining sensory quality evaluation indicators for post-curing C3F grade tobacco leaves, mathematical models were constructed using nonlinear regression, single-factor effect analysis, and two-factor interaction effect analysis.

Results 1) From budding stage to harvest stage, the ratio of leaf layer height (LLH) to leaf layer width (LLW) in the 60-90 cm layer LLH/LLW_(30-60) decreased by 10.7%, while the TIR_{(60-90)/(0-30)} increased by 22.4%. Increasing planting density reduced the TIR_{(60-90)/(30-60)} at harvest stage by 4.3%; increasing nitrogen application rate increased the TIR_{(30-60)/(0-30)} at budding stage by 1.9%; and increasing the number of retained leaves decreased the TIR_{(60-90)/(0-30)} at harvest stage by 9.4%. 2) Among the three cultivation measures, nitrogen application rate was identified as the primary factor affecting the total sensory quality score of C3F grade tobacco. 3) Based on the single-factor analysis conducted with the multivariate regression model during the buttoning stage (R² = 0.929-1.000), the results showed that the total sensory evaluation score of C3F tobacco leaves was primarily positively regulated by the upper-to-middle ratio at buttoning stage. The two-factor interaction analysis indicated that the interaction between lower-middle ratio (X₁) and height-width ratio (X₃) at budding stage enhanced the aroma quality score and the overall sensory quality score of C3F tobacco leaves, with maximum values reaching 8.99 and 99.98, respectively.

Conclusion The sensory quality of Yunyan 87 in high-altitude tobacco-growing areas is dynamically regulated by plant-type TIR. The sensory quality of C3F grade tobacco leaves is primarily influenced by nitrogen application rate and the upper-to-middle ratio of plant type at buttoning stage. Based on the analysis of the two-factor interaction effect, it is found that budding stage is the critical regulatory phase for aroma intensity formation, buttoning stage is the main influencing period for aroma quality formation, and harvest stage is the final stage for determining the overall sensory quality score.