Effects of Different Remained Leaves Amount on Metabolites of Fresh Leaves and Chemical Components of Flue-cured Tobacco

Purpose To explore the effects of different topping and remained leaves amount on the metabolites of fresh leaves and chemical components of flue-cured tobacco in field cultivation, and to screen the appropriate remained leaves amount for Baise tobacco area in Guangxi, providing a certain reference for improving the quality of tobacco leaves.

Methods Using Yunyan 116 as the experimental material, three treatments with different remained leaves amount of per plant were set: 16 (DL1), 18 (DL2), and 20 (DL3). Ultra-high performance liquid chromatography-mass spectrometry based untargeted metabolomics technology was employed to explore the effects of different remained leaves amount on the metabolites in fresh leaves of tobacco at maturity and chemical quality of flue-cured tobacco leaves.

Results Metabolomics analysis showed that there were 55 differential metabolites in DL1 vs DL2 and DL3 vs DL2 groups. Among them, the contents of amino acids (L-tryptophan, phenylalanine), esters (ethyl myristate) and alcohols (farnesol) in DL2 treatment were the highest, which contributed importantly to the aroma of tobacco leaves; the content of N-oxide nicotine, the direct conversion product of nicotine in DL1 treatment, was the highest; the contents of amino acids and alkaloids in DL3 treatment was less, indicating that the accumulation level of metabolites in leaves was lower. In flue-cured tobacco leaves, the contents of total sugar and reducing sugar, and sugar-nicotine ratio in DL2 treatment were significantly higher than those in other treatments; the content of reducing sugar in DL3 treatment was the lowest; and the content of nicotine in DL1 treatment was the highest, which was consistent with the metabolomics analysis results. On the whole, the coordination of chemical components of tobacco leaves treated with DL2 was the best.

Conclusion In Guangxi Baise tobacco area, per plant of Yunyan 116 topping and leaving 18 leaves is conducive to the accumulation of more metabolites that can improve the quality roasted tobacco leaves, such as L-tryptophan, phenylalanine, ethyl myristate, and farnesol, and at the same time, it can also make the chemical components of flue-cured tobacco leaves more coordinated, which is one of the cultivation measures to improve the quality of tobacco leaves.