Abstract: In order to identify the effects of different water loss treatments on starch metabolism in postharvest tobacco leaves, taking  Qinyan 96 as the material  this experiment set up three water loss treatments of normal treatment (CK), water loss 10% (T1) and water loss 20% (T2) to study the baking characteristics of postharvest tobacco leaves and the dynamic changes in the enzyme activity and gene expression related to starch metabolism. The results showed that: Compared with normal treatment, water loss treatment shortened the yellowing time of tobacco leaves, and the time of browning was affected. Under water loss treatment, amylose degradation of postharvest tobacco leaves was mainly concentrated in the early stage (0～18 h) while the degradation of amylopectin mainly concentrated in the late stage (after 18 h), and the total starch content of tobacco leaves decreased after water treatment. Because of the decline of DBE enzyme activity and SBE enzyme activity with the increase of postharvest time, and the corresponding enzyme genes expression level decreased (except SBE), therefore, the synthesis of postharvest tobacco starch was inhibited. However, the activity of amylase increased with the prolongation of postharvest time, the corresponding enzyme genes expression level increased, which promoted the increase of total sugar and reducing sugar content in postharvest tobacco leaves. In summary, water loss treatment improved the baking characteristics of tobacco leaves, the degradation ability of starch was enhanced and increased sugar content in postharvest tobacco, and 10% water loss treatment had the best effect. The degradation of postharvest tobacco amylose was mainly concentrated in the early postharvest (0～18 h), and amylopectin was mainly concentrated in the later stage(18～36 h).

Key words: flue-cured tobacco, baking characteristics, starch, sugar, enzyme activity, gene expression

摘要： 为明确不同失水处理对采后烟叶淀粉代谢的影响，本试验以烤烟品种秦烟96为材料，设置正常水分（CK）、失水10%（T1）和失水20%（T2）三个处理，对采后烟叶烘烤特性和淀粉代谢相关酶活性及基因表达的动态变化进行研究。结果表明，与CK相比，失水处理缩短了烟叶变黄时间，影响烟叶变褐时间。采后烟叶直链淀粉降解主要集中在失水处理前期(0～18 h)，而支链淀粉降解主要集中在失水处理后期(18 h后)，失水处理后烟叶淀粉总含量降低。由于淀粉去分支酶（DBE）活性和淀粉分支酶（SBE）活性随采后时间的延长呈逐渐下降趋势，且相应酶基因表达量降低（SBE除外），因此抑制了采后烟叶淀粉的合成；而淀粉分解酶活性随采后时间的延长呈逐渐上升趋势，且相应酶基因表达量升高，促进了采后烟叶总糖、还原糖含量增加。综上所述，失水处理改善烟叶烘烤特性，增强采后烟叶淀粉降解能力，促进采后烟叶糖含量的增加，以失水10%处理效果最优。烟叶在采后前期（0～18 h）以降解直链淀粉为主，后期（18～36 h）以降解支链淀粉为主。

关键词: 烤烟, 烘烤特性, 淀粉, 糖, 酶活性, 基因表达