Abstract: Reducing the nicotine content of tobacco leaves to a level below the threshold of addiction is a measure proposed by the World Health Organization to reduce people’s dependence on tobacco,but the nicotine content of existing low⁃nicotine varieties can not meet the preliminary standards proposed by the World Health Organization.This study explored the effect and feasibility of grafting low nicotine varieties with eggplant to reduce nicotine content,the key genes of nicotine synthesis on grafting surface were identified by PCR,and the sources of trace alkaloids in grafted tobacco leaves and their responses to varieties with different nicotine content were analyzed.The results showed that the nicotine content in middle leaves of flue⁃cured tobacco leaves of imported low⁃nicotine variety NC926 and domestic low⁃nicotine variety LAK326(CD⁃01)was 0.251 3% and 0.272 0% respectively. After grafting NC926 with eggplant,the nicotine content in fresh tobacco leaves and middle leaves of flue⁃cured tobacco leaves decreased to 0.039 5% and 0.046 0% respectively.After grafting LAK326 with eggplant,the nicotine content in fresh tobacco leaves and flue⁃cured tobacco leaves decreased to 0.037 0% and 0.039 4% respectively,which was close to or lower than the standard of 0.4 mg/g set by the World Health Organization. By comparing the expression of the key genes NtPMT1,NtPMT2,NtQPT2,NtBBLa,NtA622 of nicotine synthesis on the grafted surface of conventional high nicotine varieties and low nicotine varieties with those on the stem surface of non⁃grafted tobacco,it was found that the key genes of nicotine synthesis in the stem surface of high nicotine and low nicotine varieties were significantly up⁃regulated in different degrees after grafting,indicating that grafting measures could induce the ability of nicotine synthesis in the grafted part.It was speculated that the trace nicotine in grafted tobacco came from stem section.Moreover,varieties with different nicotine synthesis ability had different responses to grafting,and the expression of key genes of nicotine synthesis in low nicotine varieties was lower than that in high nicotine varieties.To sum up,compared with conventional high nicotine varieties grafted with eggplant,the combination of low nicotine varieties and eggplant grafting technology can further reduce the nicotine content of tobacco leaves,and the cured tobacco leaves can be close to or lower than the nicotine content limit standard set by the World Health Organization.

Key words: Tobacco, Nicotine, Low nicotine variety, Grafting of tobacco and eggplant, Grafting surface

摘要： 降低烟叶烟碱含量至低于致瘾阈值水平是世界卫生组织提出的减少人们对烟草依赖性的一项措施，但目前已有低烟碱品种的烟碱含量尚不能达到世界卫生组织提出的初步标准。为此，探索采用低烟碱品种与茄子嫁接降低低烟碱品种烟碱含量的效果和可行性，对嫁接面烟碱合成关键基因进行PCR鉴定，分析了嫁接后烟叶微量生物碱的来源和对不同烟碱含量品种的响应。结果表明，引进的低烟碱品种NC926 和国内低烟碱品种LAK326（CD-01）烤后中部叶烟碱含量分别为0.251 3% 和0.272 0%；NC926与茄子嫁接后成熟期鲜烟叶和烤后烟中部叶烟碱含量分别降至0.039 5%和0.046 0%，LAK326与茄子嫁接后成熟期鲜烟叶和烤后烟中部叶烟碱含量分别降至0.037 0%和0.039 4%，接近或低于世界卫生组织设定的烟碱含量限量标准（0.4 mg/g）。通过比较常规高烟碱品种、低烟碱品种的嫁接烟嫁接面部位和非嫁接烟相应部位茎切面烟碱合成关键基因NtPMT1、NtPMT2、NtQPT2、NtBBLa、NtA622的表达情况，发现高烟碱和低烟碱品种烟茄嫁接后茎切面的烟碱合成关键基因表达量不同程度显著上调，表明嫁接措施可诱导嫁接部位产生烟碱合成能力，推测嫁接烟微量烟碱来自茎切面，且不同烟碱合成能力烤烟品种对嫁接产生不同响应，低烟碱品种烟碱合成关键基因表达量低于高烟碱品种。综上，与常规高烟碱品种与茄子嫁接相比，低烟碱品种与茄子嫁接技术结合可进一步降低烟叶烟碱含量，烤后烟叶可接近或低于世界卫生组织设定的烟碱含量限量标准。

关键词: 烟草, 烟碱, 低烟碱品种, 烟茄嫁接, 嫁接面