Abstract: To determine the suitable nitrogen（N） application rate and clarify the nitrogen response characteristics of the new flue‐cured tobacco line YM2020，a field experiment was conducted in the tobacco‐growing area of Lushi，Western Henan，in 2024.Using the widely cultivated variety Yunyan 87 as the control，three N levels were established：low（N1，75.0 kg/ha），medium（N2，90. 0 kg/ha），and high（N3，105. 0 kg/ha）.The effects on agronomic traits，key nitrogen metabolism enzyme activities，field resistance to major diseases，economic characteristics，chemical composition，and sensory quality of cured leaves were systematically evaluated. The results revealed a fundamental difference in nitrogen‐response patterns between YM2020 and Yunyan 87. YM2020 showed the best overall performance under the N2 level.Its key agronomic traits，plant height（169.0 cm），stem circumference（13.5 cm），and leaf area（2 103.4 cm^²），were significantly better than those under the N1 and N3 treatments.The activities of nitrate reductase（NR），glutamine synthetase（GS），and glutamate synthase（GOGAT）reached peak values under N2，increasing by 32.1%—40.5% compared with the N1 level. The field incidence of brown spot（8.0%）was significantly lower than that under N3（40.0%）and under all nitrogen treatments of Yunyan 87（30.0%—50.0%）.Economic traits were outstanding，with the highest yield（3 105.0 kg/ha），output value（95 261.4 Yuan/ha），and proportion of high‐grade leaves（51.77%）.The chemical composition of cured leaves was well‐balanced，with the sugar‐to‐alkaloid ratio（9. 47）and potassium‐to‐chloride ratio（5.35）falling within the optimum ranges for high‐quality tobacco. Sensory evaluation scores were the highest（63.1 points），with notable scores for aroma quantity（6.3）and aftertaste（6.2）.In contrast，Yunyan 87 performed best under the N1 level. Increasing nitrogen application（N2/N3）suppressed the activities of key nitrogen‐metabolizing enzymes，aggravated brown spot incidence，and significantly reduced economic performance（e.g.，output value under N3 decreased by 29.1% compared with N1）and sensory quality. In conclusion，YM2020 is a medium‐nitrogen‐efficient line with strong nitrogen‐assimilation capacity that effectively translates into high‐quality leaf production.A nitrogen application rate of 90.0 kg/ha is recommended for YM2020 in the western Henan tobacco‐growing region. Yunyan 87，which has a lower nitrogen‐tolerance threshold，should be maintained under low‐nitrogen management（75.0 kg/ha）.

Key words: Flue‐cured tobacco, YM2020, Nitrogen application rate, Agronomic traits, Yield, Quality, Nitrogen‐metabolizing enzymes

摘要： 为明确烤烟新品系YM2020的适宜施氮量并揭示其氮响应特性，以主栽品种云烟87为对照，于2024年在豫西卢氏烟区设置低（N1，75.0 kg/hm^²）、中（N2，90.0 kg/hm^²）、高（N3，105.0 kg/hm^²）3个施氮水平，系统研究其对YM2020农艺性状、氮代谢关键酶活性、田间主要病害抗性、经济性状、烤后烟叶化学成分及感官质量的影响。结果表明，YM2020与云烟87对施氮量的响应模式存在显著差异。YM2020在N2水平下综合表现最优，其株高（169.0 cm）、茎围（13.5 cm）、叶面积（2 103.4 cm^²）等关键农艺性状显著优于N1和N3水平；硝酸还原酶（NR）、谷氨酰胺合成酶（GS）和谷氨酸合酶（GOGAT）活性达峰值，较N1水平提高32.1%~40.5%；田间赤星病发病率（8.0%）显著低于N3 水平（40.0%）和云烟87 各施氮处理（30.0%~50.0%）；经济性状表现突出，产量（3 105.0 kg/hm^²）、产值（95 261.4 元/hm^²）、上等烟比例（51.77%）均为最高；烤后烟叶化学成分协调，糖碱比（9.47）、钾氯比（5.35）均处于优质烟适宜区间；感官评吸总分（63.1分）领先，香气量（6.3分）和余味（6.2分）得分突出。云烟87则在N1水平表现最佳，增施氮肥（N2、N3）导致氮代谢关键酶活性受抑、赤星病加重、经济性状（如N3产值较N1下降29.1%）和感官品质显著下降。综上，YM2020属中氮高效型品系，其氮同化能力强且能有效转化形成优质烟叶，推荐其在豫西烟区的施氮量为90.0 kg/hm²；云烟87氮耐受阈值较低，宜维持低氮（75.0 kg/hm^²）水平管理。

关键词: 烤烟, YM2020, 施氮量, 农艺性状, 产量, 品质, 氮代谢酶