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

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