In order to investigate the changes of secondary metabolites content of alfalfa induced by thrips Odontothrips loti damaging, two alfalfa strains, one resistant to thrips (R-1) and the other susceptible to thrips (I-1) , were chosen to measure the phenols and lignin contents of alfalfa leaves under infestation with thrips at different densities (0, 1, 3, 5, 7 thrips x branch(-1), and 0 thrip x branch(-1) as control). After infestation 7 days, the polyphenols, tannin and condensed tannin contents increased in both leaves of R-l and I-i with the increasing thrips density, the simple phenols content had no significant difference, while the lignin content increased significantly compared with the control. After infestation 14 days, the polyphenols, tannin, condensed tannin and lignin contents in both leaves of R-1 and I-1 increased obviously with the increasing thrips density, while the simple phenols content had no significant difference. The lignin content increased significantly, and was significantly higher under 7 thrips x branch(-1) than under the control. After infestation 21 days, the polyphenols, tannin, and lignin contents in both leaves of R-1 and I-1 increased obviously with the increasing thrips density, and were the highest under 7 thrips x branch(-1). Simple phenols content of I-1 strain was increased significantly, but that of R-1 strain had no significant change. The condensed tannin content in both leaves of R-1 and I-1 was not obvious compared with the control. Phenols and lignin contents in R-1 and I-1 leaves increased obviously after thrips infestation, and the polyphenols, tannin and lignin contents increased faster in R-1 strain than in I-1 strain. Thrips infestation had inductive effects on phenols and lignin contents of alfalfa, which could be used to evaluate the resistance of alfalfa.

为了探索营养元素分配利用与苜蓿抗蓟马的关系,本研究以抗蓟马苜蓿R-1和感蓟马苜蓿I-1为材料,测定了牛角花齿蓟马Odontothrips loti不同虫口压力下苜蓿根、茎、叶中N,P,K和Ca含量的变化.结果表明,随着虫口密度的增大:(1)R-1和I-1茎中N含量均显著升高,叶中N含量均显著下降(P＜0.05)；R-1根中N含量降低,I-1根中N含量先降低后升高.(2)R-1茎中P含量先升高后降低,I-1茎中变化不显著；R-1叶中P含量在低虫口压力下持续升高,7头/枝条密度时下降,I-1叶中的P含量显著下降；R-1和I-1根的P含量均显著高于对照(P＜0.05).(3)R-1和I-1茎、叶中K含量均呈先增加后降低的趋势；R-1和I-1根中K含量显著下降(P＜0.05).(4)R-1茎、叶中的Ca含量均显著升高(P＜0.05),I-1茎中Ca含量先降低后升高,叶中Ca含量在7头/枝条时显著低于对照,其他密度下与对照差异不显著；R-1根中Ca含量与对照差异不显著,I-1根中的Ca含量均显著下降.抗感蓟马苜蓿体内不同营养元素含量在蓟马为害后变化不同,R-1的受害指数极显著低于I-1 (P＜0.01),R-1表现出更好的抗虫性.

The soluble protein and MDA in different alfalfa varieties(with different levels of resistance to thrips) damaged by Odontothrips loti were determined.The results showed that soluble protein content decreased at 3 leaf stage and increased at 6 leaf stage.In 3 and 6 leaf stages,the soluble protein contents of resistant alfalfa were significantly higher than that of susceptible varieties(P0.05).The contents of MDA increased significantly in 3 and 6 leaf stages(P0.05),but accumulations of MDA in susceptible alfalfa were significantly higher than that of resistant varieties(P0.05).These might be related to the membrane lipid peroxidation suspending,or the defensive chemical metabolites stimulating the enzymes in alfalfa,and which might enhance the resistance of alfalfa to thrips.