| The leafy vegetable sweetpotato,with many vine branches and many topping times,is mainly picked at its shoot tips.It is deeply favored by consumers and industrialized owners for its richness in much nutrients and natural antioxidant active substances such as polyphenols,total flavonoids,and chlorogenic acid with various physiological health functions such as anti-aging,anti-cancer and for its eating crispy,tender,sweety,and for its high output.This thesis took 10 varieties of leaf-vegetable sweetpotato from the national joint identification test in Chongqing from 2018 to 2019 as the research object.On the basis of measuring the agronomic traits,the three functional substances(polyphenols,total flavonoids and chlorogenic acid)in each part of shoot tips were determined during harvesting period.In order to lay a theoretical foundation for the selection and breeding of the yield and quality of leafy vegetable sweetpotato varieties in the future,present paper further analyzed their yield composition characteristics of shoot tips and their relationship with agronomic traits,the correlation among the three functional substances of shoot tips as well as the differences between parts and varieties,the stability during topping period.The chlorogenic acid content and its ABTS free radical scavenging ability and the changes of the three key enzyme genes relative to express quantity were also studied.The main research results are as follows:1.Variance analysis showed that the yield composition,fresh mass of each part,21 agronomic traits,and the contents of the three functional substances(polyphenols,total flavonoids and chlorogenic acid)in the shoot tips among 10 varieties of leaf-vegetable sweetpotato are all significantly affected by environmental factors and genetic types,in which traits associated with petiole mainly were influenced by genotype,while the rest of the characters and functional substance content were mainly affected by environmental factors in topping period.2.The analysis of 21 agronomic traits of shoot tip showed that the petiole length was closely related to the spatial configuration of foliage and the overall growth of shoot tip,and it was an important organ that influences shoot tip yield.By using plus or minus sign,subordinate function analysis method and principal component analysis,21 agronomic traits of shoot tip were analyzed and showed that 10 varieties of leaf-vegetable sweetpotato had different agronomic traits characteristics.Present study put forward for the first time that leaf-vegetable sweetpotato would be divided into five types,which are the foliage-type(Guishucai 14-7,Fucai 13-14),the petiole-type(Qiancaishu NO.2,Fushu 7-6),the stem-type(Xiangcaishu NO.3,Fucaishu 25),the branch-ype(EC15,Haida7798),and the crossing-type(Guangcaishu NO.7,Shulu NO.2).Besides,The petioletype of leaf-vegetable sweetpotato had a relatively high vine yield,while the leaf-type of leaf-vegetable sweetpotato had a relatively low vine yield.3.By analyzing the three functional substances in each part and the whole shoot tips of 10 varieties of leafy vegetable sweetpotato during 12 harvesting periods of two years,it were found that the variation coefficients of the contents of the polyphenol,total flavonoid and chlorogenic in foliage and the whole shoot tips were nearly the same.The contents of the three active substances in foliage,stem,and petiole and their proportion in the contributions to the overall shoot tip content was foliage > stem > petiole.The contents of the three active substances in shoot tip were significantly higher than those in stem and petiole,and foliage was the significant organ in influencing the functional substance content of stem tip.The contents of three functional substances in the whole shoot tip and foliage parts were significantly positively correlated with the dry matter contents in foliage and petiole,this revealed that besides foliage,petiole was also an important part that affected the content of functional substances in shoot tip.Moreover,it were also found that the contents of polyphenol,total flavonoid and chlorogenic acid in three parts and in shoot tip,were significantly positively correlated with each other.This indicated that when the contents of total flavonoids and chlorogenic acid were high,the content of polyphenols was correspondingly high.Among 10 leafy type varieties,the content of functional components of Fucaishu 25,Guangcaishu NO.7,Shulv NO.2,Haida 7798 and Qiancaishu NO.2 of each parts were relatively high,and those of Guangcaishu NO.7,Guicaishu 14-7,Haida 7798 and Qian Caishu NO.2 of each parts of shoot tips or of shoot tip were relatively stable in harvest period.4.The correlation between the content of chlorogenic acid in foliage and the EC50 value of antioxidant activity indicated that the content of chlorogenic acid and the EC50 value generally show a significant or extremely significant negative correlation,that were to say,the higher the content of chlorogenic acid,the lower the EC50 value,and the stronger its ability of antioxidant activity.The relative expression of the three key genes of Ib PAL,Ib C3 H and Ib HCT in the synthesis pathway of chlorogenic acid showed that the relative expression changes in different harvest periods and different varieties were inconsistent,and the correlation with the content of chlorogenic acid was some showing positive correlation and some showing negative correlation,which indicates that the accumulation of chlorogenic acid in shoot tips is not limited to the synthetic pathway,but also related to its transportation between different parts of the sweetpotato.Conclusion: Petiole was an important component that affects the difference in the vine yield of shoot tip among varieties.Leafy vegetable sweetpotato varieties would be divided into five types,which were foliage-type,petiole-type,stem-type,branch-type and crossing-type,and meanwhile,the yield of petiole-type was relatively higher while that of stem-type varieties was relatively lower.Then,the foliage and petiole and their dry matter content were important parts and factors that affect the contents of polyphenols,total flavonoids and chlorogenic acid in the whole and different parts of the shoot tip,and there was a significant positive correlation with the content of functional substances(this article is represented by chlorogenic acid)and its ABTS radical scavenging ability.Last,among the 10 varieties,Qiancaishu NO.2,a petiole-type variety,was a comprehensive variety for its high vine yield,high content of functional substances and relatively stable in harvesting period. |
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