Abstract: In order to explore the effect of potassium application on carbohydrate distribution and alfalfa (Medicago sativa)resistance to thrips,Gannong No. 3 and Gannong No. 9 alfalfa variety were used as the experimental materials,and the dominant insect pest on alfalfa, Odontothrips loti,was selected as research project. The damage index of alfalfa were evaluated,and the carbohydrate content in roots,stems and leaves of alfalfa potted in net house under different potassium application levels were determined. The results showed that,the damage index of alfalfa decreased with potassium application,and the content of soluble sugar and starch in organs increased,while the root-to-shoot ratio of soluble sugar and starch increased. The soluble sugar content in alfalfa leaves reached the highest at 10 days of damage,and the soluble sugar content in the stem reached highest at 15 days of damage. The soluble sugar content in roots and the starch content in organs continued to increase. The leaf-to-stem ratio of soluble sugar reached the highest when damaged by thrips for 10 days,the leaf-stem ratio of starch did not change significantly,and the root to shoot ratio of soluble sugar and starch continued to increase. Potassium application increased the carbohydrate content of alfalfa and regulated the reasonable distribution of soluble sugar and starch in alfalfa organs,thereby enhanced the tolerance of alfalfa to thrips. The resistance performance of Gannong No. 9 was better than that of Gannong No.3 The optimum potassium level for enhancing alfalfa resistance to thrips in this experiment was 0.6 g·(10 kg)^-1 soil.

Key words: Potassium, Odontothrips loti, Alfalfa, Carbohydrate, Distribution, Tolerance to thrips

摘要： 为了探索施钾对苜蓿（Medicago sativa）叶茎根碳水化合物的分配与苜蓿抗蓟马的关系，本试验以紫花苜蓿‘甘农3号’和‘甘农9号’为材料，以牛角花齿蓟马（Odontothrips loti）为研究对象，在网室盆栽条件下，评价不同钾水平下苜蓿的受害程度，并测定了叶茎根中可溶性糖和淀粉含量。结果表明：施钾后，苜蓿的受害指数下降，各器官中的可溶性糖与淀粉含量及其根冠比均升高。随着受害时间的持续，各钾水平下苜蓿叶中可溶性糖含量在受害10 d时最高，茎中可溶性糖含量在受害15 d时最高，根中可溶性糖含量及各器官中淀粉含量均持续增加；可溶性糖的叶茎比在受害10 d时最高，淀粉的叶茎比变化不显著，可溶性糖和淀粉的根冠比均持续升高。施钾提高了苜蓿的碳水化合物含量，并调控其在苜蓿各器官中的合理分配，进而增强了苜蓿对蓟马的耐害性。‘甘农9号’抗性表现较‘甘农3号’好，本试验中最适施钾量为0.6 g·（10 kg）^-1土。

关键词: 钾, 牛角花齿蓟马, 苜蓿, 碳水化合物, 分配, 耐害性