| Flavor type of flue-cured tobacco is one of the important characters of Chinese-style cigarette.It is an essential basis for quality evaluation and industrial utilization of flue-cured tobacco.The mechanism of flavor type formation of flue-cured tobacco was a hotspot to study on the high quality character formation of flue-cured tobacco.As reported,the same cultivar of flue-cured tobacco showed different flavor characteristics in different ecological regions.A study on the material basis and the eco-physiological mechanism of different flavor type formation of flue-cured tobacco is of great significance of realizing sustainable development of flue-cured tobacco industry.The flue-cured tobacco cultivar K326 that own the better growth vigour in the field and fine process properties,which praised by the industrial enterprises.It also exhibits different flavor characteristics in different ecological regions,providing a valuable experimental material for our exploration on the influence of different ecological environment to the quality of flue-cured tobacco.In this study,K326 was used as the research object.We analyzed what was the mechanism that regulated the flavor type formation of flue-cured tobacco,and clarified the effects of different ecological environment factors on the differences of quality characteristic of flue-cured tobacco.The aim is to explore the ecological regulation mechanism of flavor type formation of flue-cured tobacco K326 affected by the ecological environment.It has an important significance to guide the flue-cured tobacco production as well as to improve the quality and industrial availability of tobacco.The results were as below.1.The main quality characteristics of flue-cured tobacco K326 and the ecological environmental difference among three ecoregions(Taining county of Fujian province,Xiangyun country of Yunan province and Yiyang country of Henan province)were analyzed.The results showed that flue-cured tobacco K326 plants in Taining and Xiangyun ecoregions were relatively larger,and plants in Yiyang ecoregion were small.The contents of chlorophyll and its degradation product of neophytadiene,carotenoids and its degradation products(crocein aldehyde,β-rings citral,β-dihydrogen damascenone,β-damascenone,dihydroactinidiolide,etc.),the total carotenoid degradation products,total sugar and reducing sugar in flue-cured tobacco from Taining and Xiangyun ecoregions were higher than that in Yiyang ecoregion.The contents of carotenoid degradation products(solanone,megastigmatrienone1,megastigmatrienone 2 and megastigmatrienone 4),phenylalanine degradation products(benzaldehyde and phenylacetaldehyde),total phenylalanine degradation products,total alkali and chlorine in flue-cured tobacco from Yiyang ecoregion were higher than that in Taining and Xiangyun ecoregions.The contents of chlorophyll,crocein aldehyde,β-rings citral,dihydroactinidiolide in flue-cured tobacco from Taining ecoregion were higher than that in Xiangyun ecoregion,but the contents of total alkali and β-damascenone were less than those in Xiangyun ecoregion.The sensory evaluation showed flue-cured tobacco were delicate flavor types in Taining and Xiangyun ecoregions,and was strong flavor type in Yiyang ecoregion.Obviously,there were differences in the appearance,the contents of the routine chemical components and the aroma substances,as well as the flavor type of the flue-cured tobacco K326 in different ecological regions.Further analysis of the ecological environmental conditions in different ecoregions showed that the average temperature in Taining and Xiangyun ecoregions was lower than that in Yiyang ecoregion,while the rainfall and intensity of UV-B radiation were more than those in Yiyang ecoregion.Sunshine hours in Xiangyun were the most,followed in Yiyang,while Taining ecoregion has the least sunshine hours.The rainfall in Taining ecoregion was more than that in Xiangyun ecoregion,while with a lower intensity of UV-B radiation.It revealed that there were obvious differences in the climatic conditions in different ecological regions.The analysis results of rhizosphere micro-ecology of flue-cured tobacco showed that the soil of Taining and Xiangyun ecoregions was weak acid(pH5.02 and pH5.28,respectively).The contents of soil organic matter,nitrogen and potassium were higher than those in Yiyang ecoregion.Among them,the contents of soil organic matter and nitrogen were higher in Taining,while the content of soil potassium was higher in Xiangyun.The soil of Yiyang ecoregion was alkalescence with a pH value of 7.49.The cultivable microbial quantity of rhizosphere soil,was relatively higher in Taining and Xiangyun ecoregions.Microbial functional diversity analysis suggested that the rhizospheric soils in Taining and Xiangyun ecoregions were the most conducive to the growth of the microorganisms with carboxylic acids,copolymers,sugar and amino acids as substrate;the rhizospheric soil in Yiyang ecoregion was the most conducive to the growth of the microorganisms with amine and phenolic acids as substrate.Therefore,there were differences in average temperature,rainfall,sunshine hours,UV-B radiation,soil nutrients,soil pH,cultivable microbial quantity and microbial functional diversity of rhizosphere soil in distinct ecoregions.2.The rhizospheric soils of flue-cured tobacco were collected from Taining,Xiangyun,and Yiyang ecoregions,respectively.Then performed in Taining ecoregion to explore the effect of different soils on flavor type formation of flue-cured tobacco K326 under the same climate condition.The results showed that the change trend of agronomic characters of flue-cured tobacco,the content of chlorophyll,carotenoids and carotenoid degradation products(crocein aldehydes,β-damascenone,megastigmatrienone1,megastigmatrienone 2,megastigmatrienone 3,megastigmatrienone 4,etc.),phenylalanine degradation products(benzaldehyde and phenylacetaldehyde),total quantity,total sugar and reducing sugar in flue-cured tobacco under different soils of treatments were all similar to their corresponding ecoregions.However,the change trend of content of total alkali,solanone,neophytadiene,β-damascenone,dihydroactinidiolide,etc.,under different soils of treatments were contrary to their corresponding ecoregions.Analysis of metabolomics showed that a total of 65 differential metabolites were identified,which mainly involved in glycolysis and sugar metabolism,shikimic acid metabolism,amino acid metabolism,fatty acid metabolism,alkaloid metabolism and terpenoid metabolism.The levels of carbohydrates,amino acids,most shikimic acid metabolism in flue-cured tobacco were higher under soils of Taining and Xiangyun treatments.Sensory evaluation results showed flue-cured tobacco under soils of Taining and Xiangyun treatments were delicate flavor types,and the delicate flavor type of tobacco under soil of Yiyang treatment was not prominent but still dominated by partial delicate flavor type.Visibly,soil may not be the key factor to decide flavor type formation of flue-cured tobacco.It’s speculated that climate may be the main ecological factor affecting flavor type formation of flued-cured tobacco.3.This study investigated the physiological and ecological effects of different climate conditions(Taining climate,Xiangyun climate and Yiyang climate)under the same soil(plant nutrition soil)on flavor type formation of flue-cured tobacco K326,and explored the influence on physiological and biochemical properties of flue-cured tobacco,combined with different temperatures,different water and UV-B radiation and other climatic factors controlling experiment.The changes of trend of indicators,including agronomic characters,contents of pigments(chlorophyll and carotenoids),carotenoid and its relevant degradation products,phenylalanine degradation products and routine chemical components,etc.,in flue-cured tobacco under different climate treatments were all similar to their corresponding ecoregions.Meanwhile,the study found that although there are some differences in flue-cured tobacco between Taining climate and Xiangyun climate treatments,on the whole,they were similar to each index.Analysis of metabolomics showed that a total of 66 differential metabolites were identified,which mainly involved in glycolysis and sugar metabolism,TCA cycle,shikimic acid metabolism,amino acid metabolism,fatty acid metabolism,alkaloid metabolism and terpenoid metabolism.The levels of carbohydrates,amino acids,alkaloid and most shikimic acid metabolism were higher in flue-cured tobacco under Yiyang climatic condition than that in Taining climate and Xiangyun climate.Contents of metabolites were similar under Taining climate and Xiangyun climate.Correlation analysis between differential metabolites and climate factors found that the temperature and UV-B radiation have varying degrees of impact on metabolite of glucose metabolism,shikimic acid metabolism and alkaloid metabolism,and plastid pigments.They had significant positive correlation with temperature,and negatively correlated with the dose of UV-B radiation.This indicated that the content difference of flue-eured tobacco metabolites in the same soil condition may be caused by the difference of temperature and UV-B radiation.The results of the sensory evaluation showed that the flue-cured tobacco were delicate flavor types under Taining climate and Xiangyun climate treatments,and was strong flavor type under Yiyang climate treatment.The above results showed that the climatic conditions may be the key factor deciding the flavor type formation of flue-cured tobacco.4.According to the comparative analysis of flue-cured tobacco between in the different soils with the same climatic condition and in the different climatic conditions with the same soil treatments,flavor types of flue-cured tobacco under Taining and Xiangyun climatic treatments were the delicate flavor,which indicated that the two climatic conditions have the climatic characteristics of delicate flavor type production.Furthermore,the delicate flavor type was also found in the flue-cured tobacco under Taining soil and Xiangyun soil treatments,indicating that the two soil conditions have the soil characteristics of delicate flavor type production.The further comprehensive analysis on the soil and climate factors demonstrated that when ecological conditions could satisfy the following conditions of the soil aspects:weak acid soil with pH5.02 or pH5.28,higher contents of soil organic matter,nitrogen and potassium;the climate aspects:more rainfall,especially in the mature period,the average growth temperature at about 20 ℃,the appropriate doses of UV-B radiation,it could be conducive to form delicate flavor type.Nevertheless,when ecological conditions could match the following conditions of the soil aspects:alkaline soils with pH 7.5,low contents of soil organic matter,nitrogen and potassium;the climate aspects:less rainfall,the average growth temperature at about 25 ℃,it could be helpful to form strong flavor type of flue-cured tobacco.Flue-cured tobacco from Taining and Xiangyun ecoregions were both delicate flavor type,but there was still a difference between them.In addition to the antecedent precipitation and temperature differences,the different UV-B radiation does may be one main reason to produce the difference.In summary,this study indicated that the differenct contents of routine chemical components and aroma substances in flue-cured tobacco caused by different ecological environment,thereby affecting different flavor type formation of flue-cured tobacco.As the ecological environment is one complex of several factors,the different factor may have a different influence on flavor type formation of flue-cured tobacco.The study had a further discussion on the regulation mechanism of the ecological environment on the production of flavor type of flue-cured tobacco K326.The results showed that flue-cured tobacco were all delicate flavor type under different ecological soils treatments(Taining soil,Xiangyun soil,Yiyang soil)in the same climate condition.Although the delicate flavor type of flue-cured tobacco under Yiyang soil treatment was not prominent,it was partial delicate flavor type.Combined with the change of metabolites,we could conclude that different soils have different impacts on the contents of metabolites in flue-cured tobacco.However,compared with the result of metabolomics of flue-cured tobacco under different climatic conditions,the content difference of metabolites was relatively small,which may not achieve the influence degree of changing the flavor type of flue-cured tobacco.The results of experiment with different climate treatments in the same soil showed that flavor types of flue-cured tobacco were similar to their corresponding ecoregions,indicating that the climatic condition was the key ecological factor affecting flavor type of flue-cured tobacco among the ecological environment factors.The research revealed the physiological and ecological mechanism of different flavor type of flue-cured tobacco K326 under different conditions.These results will provid theoretical basis and technical support for better highlighting flavor type of the flue-cured tobacco K326 through the rational distribution of crops and different cultivation techniques. |
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