Effects of Transplanting Time and Topping Period on Carbon Metabolism and Related Gene Expression in Upper Leaves of Flue-Cured Tobacco

Zhang Yu; Qian Xuesong; Wu Xueqiao; Li Zhineng; Gao Junyi; Li Pengzhi; Xiong Jing; Gao Huanye

doi:10.14083/j.issn.1001-4942.2025.12.006

Abstract：To explore the optimal transplanting time and topping period combination for Yunyan 87 flue-cured tobacco in the Heishi tobacco area of Weining,and to further improve the quality of upper tobacco leav-es,this experiment used a two-factor randomized block design with transplanting time and topping period as factors.Three transplanting times(April 10,April 20,April 30)and three topping periods(budding,early flowering,full flowering)were set,forming a total of nine combination treatments(T1 to T9),and their inter-action effects on content of carbon metabolites,key enzyme activities,and related gene expression in upper leaves of flue-cured tobacco were studied.The results showed that under different transplanting times,topping at early flowering was the most favorable period for promoting the accumulation of carbon metabolites(total sugar,reducing sugar and starch)in upper leaves with the treatment of topping in early flowering period and transplanting on April 30(T8)showing the best.The activity of invertase(INV)in upper leaves was higher in the treatments of topping in budding period and transplanting on April 10(T1)and topping in early flower-ing period and transplanting on April 20(T5).The sucrose synthase(SS)activity was higher in the treat-ments of T7(topping in budding period and transplanting on April 30)and T8.The relative expression of the INV gene NtINV was higher in T5 and T9(topping in full flowering period and transplanting on April 30)treatments.The relative expression of the SS gene NtSS was higher in the treatments of T6(topping in full flowering period and transplanting on April 20)and T9.The contents of total sugar,reducing sugar and starch in cured upper leaves were higher in T3(topping in full flowering period and transplanting on April 10)and T8 treatments,and the chemical composition coordination performed better,which were beneficial for impro-ving tobacco leaf quality.The results of correlation analysis showed that the total sugar content in fresh tobacco leaves was significantly positively correlated with the starch content of cured tobacco leaves,and the reducing sugar content of fresh tobacco leaves was extremely significantly positively correlated with the starch content of cured tobacco leaves.In summary,it could be concluded that transplanting on April 30 combined with topping in early flowering periodwas the most beneficial for the carbon metabolism activity and quality improvement of upper tobacco leaves in the Heishi tobacco area of Weining.