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Difference of Curing Characteristics of Upper Leaves With Different Maturity in Different Flue-cured Tobacco Varieties
WU Shengjiang, MO Jingjing, LOU Yuanfei, TU Yonggao, ZHAO Huina, ZHAN Jun, WEI Kesu, ZHAO Degang
In order to investigate curing characteristics of upper tobacco leaves, the difference of water loss rate, yellowing and browning characteristics, chlorophyll relative content (SPAD), color values, polyphenol oxidase (PPO) activity and chemical composition content of the different maturity leaves of K326, Bi’na1, Zunyan6, Guiyan1, Guiyan4 and Honghuadajinyuan (Hongda) were studied during curing or during drawer testing. The results showed that Bi’na1 had smaller water loss rates while Hongda and Guiyan1 had larger water loss rates; Bi’na1 and K326 had shorter yellowing time while Hongda had a longer yellowing time during curing and drawer testing. The average PPO activity of Bi’na1 was less than 0.4 U and that of Guiyan1 was larger than 0.5 U during curing. As for chlorophyll relative content, Hongda had larger SPAD values, then were Zunyan6 and Guiyan1, and the last were Bi’na1, Guiyan4 and K326 during drawer testing. Hongda and Zunyan6 showed a relatively poor color values, and Guiyan1 showed a more serious browning. However, Bi’na1 had a lighter browning during drawer testing. Moreover, flue-cured tobacco leaves of Bi’na1, Guiyan4 and Zunyan6 had a relatively suitable chemical composition content. Following progressive improvement of tobacco leaves maturity levels, the yellowing time of fresh tobacco leaves was shortened and the activity of PPO increased during curing, the total content plant alkaloid and nitrogen decreased, and the content of water-soluble total sugar and reducing sugar increased. In addition, the yellowing time and browning time of tobacco leaves were shortened, the SPAD value was reduced, and the color showed better before the leaf became browning with the improvement of tobacco leaf maturity levels during drawer testing. Variety and maturity not only affected the leaf phenotype, but also had a significant impact on its intrinsic physiology. The curing characteristics of different flue-cured tobacco varieties were not only closely related to the chemical composition, but also the genotypes. As for drawer testing, SPAD value could be used as a phenotypic indicator for judging the easy curing portential, and the color parameters could be used as a phenotypic indicator for judging the easy and endurable curing portential. Taken together, K326, Bi’na1, Guiyan1 and Guiyan4 had a better easy curing portential, then was Zunyan6, and Hongda showed the worst performance. In addition, Bi’na1 had a better endurable curing portential, then were K326, Guiyan4, Hongda and Zunyan6, and Guiyan1 showed the worst performance. According to the difference of curing characteristics of different flue-cured tobacco varieties, we have put forward some specific measures for different tobacco varieties curing, which lay the theoretical foundation for different flue-cured tobacco varieties curing and the improvement of upper tobacco quality.
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