Agronomic Practices Research On Decreasing Tobacco-specific Nitrosamines Of Burley Tobacco By Regulating Its Precursors

With the development of society and economy,the safety of tobacco and tobacco products has been paid much more attention.Tobacco-specific N-nitrosamines(TSNAs)are carcinogenic,especially N-nitrosonornicotine(NNN)and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK)have been classified as Group I carcinogens(the highest designation)by International Agency for Research on Cancer due to its high toxicity.Burley tobacco is an important raw material for blended cigarettes,but its higher TSNAs content has limited its sustainable use.Reducing TSNAs contents and maintained the quality of burley tobacco is a difficult problem for tobacco industry.The objective of the present study was to to find a stable and reliable technique to reduce the burley tobacco TSNA and maintain the original style of burley tobacco on the basis of reduction of TSNA s precursors by changing the agronomic measures in the field.This study investigated the effects of BSM,BSM coupled with other agronomic measures and harvesting method(pre-withering time)on TSNAs content and quality of burley tobacco.The main findings were as follows:1.Effects of bsm on TSNAs content and quality of burley tobacco.BSM is a signal molecule that could regulate tobacco mechanical damage developed in the laboratory-based insect-to-tobacco interaction research,which has been shown to affect the synthesis and transport of alkaloid and nitrate content after tobacco topping.To study the effects of BSM application on TSNAs content and quality of burley tobacco.Field experiments were conducted in 2014 and 2015 at Dazhou,Sichuan Province,China.The results showed that total TSNAs,NNN and NNK contents were reduced by 10.40 ~ 24.75%,by 9.01~24.23% and 11.43~26.86%,respectively.At the same time,the application of BSM could effectively reduce the alkaloid,nitrate and nitrite contents in air-cured tobacco leaves.In this experiment,the application of BSM had no negative effects on the quality of burley tobacco,the aroma is more pure,undersirable smell was reduced.Therefore,the application of BSM in burley tobacco production was able to maintain the characteristics of burley tobacco while reducing TSNAs,and enhancing the industrial availability of burley tobacco.2.Effects of nitrogen application rate,topping time and BSM on TSNAs content and quality of burley tobaccoTo reveal the influence of different cultivation measures to TSNAs content in air-curd burley tobacco and its quality,according to the actual situation of burley tobacco production areas in sichuan dazhou,the orthogonal experiment was conducted to investigated the effects of nitrogen application rate,topping time and BSM doses on TSNAs contents and quality of burley tobacco.The results showed that:(1)Nitrogen application rate was the main factor affecting the change of TSNAs content in burley tobacco,and the difference of four individual TSNAs and total TSNAs contents in the middle and upper leaves was also significant.TSNAs and its precursors increased with the increase of nitrogen application rate.Therefore,the control of nitrogen application rate in Dazhou tobacco zone is not only the need to reduce TSNAs contents,but also the need to improve the quality of tobacco leaves.(2)The effects of topping time on the four individual TSNAs and total TSNAs contents in the middle and upper leaves of burley tobacco were significantly different.At the same time,the contents of four individual TSNAs and its precursors were lower.Therefore,it is also an important measure to reduce TSNAs contents and improve the safety of tobacco leaves.(3)After the application of BSM,the contents of TSNAs and its precursors in air-cured burley tobacco leaves were lower.(4)Comprehensive consideration,the combination of the application rate of 210 kg·hm-2 + topping at budding stage + smearing 0.3 μmol·L-1 BSM in Dazhou area could effectively reduce TSNAs content,while the conventional chemical composition is coordinated,and the proportion of the middle-high class leaf was high.It is particularly important that this combination not only maintains and but also improves the sensory quality of burley tobacco.3.Effects of variety,nitrogen application rate and BSM on TSNAs content and quality of burley tobacco.The experiment was conducted in Jianshi,Enshi,Hubei,China.According to the actual situation of Enshi burley tobacco planting area,the orthogonal experiment was conducted to investigated the effects of nitrogen application rate,varieties and BSM dose on TSNAs content and quality of burley tobacco.The results showed that:(1)The varieties were the main factors affecting the content of NNN,nicotine and nicotine in burley tobacco,and contents of NNN and the total TSNAs in the middle tobacco leaves of Eyan1 LC and Eyan3 LC were significantly lower than those in the TN90.These suggested that selection and remove the “low conversion” variety could reduce the TSNAs content and improve the safety of tobacco.(2)The effects of nitrogen application rate on the contents of on four individual TSNAs and total TSNAs contents in middle and upper tobacco leaves were significantly different.Therefore,the appropriate management of nitrogen fertilization,according to the local practice,is an effective measure to reduce TSNA levels.(3)After the application of BSM,the contents of NNN and total TSNAs in air-cured burley tobacco leaves were lower.(4)Therefore in Hubei Burley tobacco areas,the application of low nicotine conversion varieties to reduce TSNA contents in the production of burley tobacco is important.The appropriate management of nitrogen fertilization and combined with the application of BSM were able to reduce TSNA contents and improve the safety of tobacco leaves.4.Effects of harvesting method(pre-withering time)on TSNAs content and quality of burley tobaccoExperiment was conducted to investigate the effects of different pre-withering time on TSNAs content and quality of burley tobacco.The results showed that:(1)In Enshi burley tobacco planting area,TSNAs content was increased with the increase of pre-wilting time(3 to 7d).(2)The appearance quality,smoking quality and conventional chemical components of burley tobacco was gradually become worse with the increase of pre-withering time.