Abstract: To explore the longitudinal distribution law of volatile compounds in upper tobacco leaves from Yunnan Province，Tobacco leaves of cultivar Yunyan 100 at grade B2F，collected from Luoping County，Qujing City，Yunnan Province，were used as the research object，and evenly divided into 10 segments（Q1—Q10）along the longitudinal direction of the main vein. Gas chromatography⁃mass spectrometry（GC⁃MS） was employed to determine the contents of volatile compounds.Subsequently，hierarchical cluster analysis was performed for differential grouping of these sections，and orthogonal partial least squares discriminant analysis（OPLS⁃DA）was used to screen for differential aroma⁃active compounds among the groups. The results showed that 145 volatile compounds（predominantly hydrocarbons，alcohols and ketones）were identified in 10 segments. The total content exhibited a trend of increasing first，then decreasing and increasing again along the direction from leaf tip to leaf base（Q1 to Q10）.The total amount of Q7 was the highest（129.66 μg/g）and the total amount of Q9 was the lowest（48.11 μg/g）.Hierarchical clustering divided tobacco leaves into three characteristic sections：upper section（Q1—Q4），middle section（Q5—Q7）and lower section（Q8—Q10）.Based on the OPLS⁃DA model，39 differential volatile compounds（variable importance projection≥1，difference multiple≥2 or difference multiple≤0.5，p<0.05）were further screened.Among them，the number of up⁃regulated compounds in the middle section was significantly higher than that in the upper and lower sections，including solanone，damascenone，dihydroactinidiolide and other key aroma compounds.Sensory evaluation revealed that the middle section of tobacco leaves was significantly superior to the upper and lower segments of tobacco leaves in terms of aroma intensity，aroma quality，aftertaste，and comprehensive score，and this result was consistent with the distribution pattern of volatile compounds.In conclusion，this study clarified the gradient distribution pattern of volatile compounds along the longitudinal axis of tobacco leaves，especially revealed the superiority of the middle section of tobacco leaves in aroma quality，providing a scientific basis for the refined grading of tobacco leaves and the high⁃value utilization of tobacco resources.

Key words: Flue?cured tobacco, Tobacco leaf slicing, Cluster analysis, Orthogonal partial least squares discriminant analysis, Differential volatile compound, Sensory quality

摘要： 为探究云南省上部烟叶中挥发性物质的纵向分布规律，以采自云南省曲靖市罗平县的云烟100 B2F等级烟叶为研究对象，沿烟叶主脉纵向均匀划分为10个区段（Q1—Q10），采用气相色谱-质谱联用技术（GC-MS）测定挥发性物质含量，结合层次聚类分析对区段进行差异分组，并通过正交偏最小二乘判别分析（OPLS-DA）筛选组间差异香味物质。结果表明，在10个区段中共鉴定出145种挥发性物质（以烃类、醇类和酮类为主），其挥发性化合物总量沿叶尖至叶基（Q1—Q10）呈现先升高后降低再升高的变化趋势，Q7总量最高（129.66 μg/g），Q9总量最低（48.11 μg/g）；层次聚类将烟叶划分为上段（Q1—Q4）、中段（Q5—Q7）和下段（Q8—Q10）3个特征区段。于OPLS-DA模型进一步筛选出39种差异挥发性物质（变量重要性投影≥1、差异倍数≥2或差异倍数≤0.5、p<0.05），其中中段上调物质数量明显多于上段和下段，包含茄尼酮、大马士酮、二氢猕猴桃内酯等关键致香物质。通过感官评价发现，中段烟叶在香气量、香气质、余味及综合得分等方面均显著优于上段和下段烟叶，这一结果与挥发性物质的分布规律一致。综上，明确挥发性物质在烟叶纵向分布上的梯度规律，尤其揭示中段烟叶在香气品质上的优势，为烟叶原料高值化利用提供了科学依据。

关键词: 烤烟, 烟叶分切, 聚类分析, 正交偏最小二乘判别分析, 差异挥发性物质, 感官质量