Effect of Odontothrips loti damage on MDA content and defensive enzyme activity in alfalfa plants | 牛角花齿蓟马为害对紫花苜蓿MDA含量及防御酶活性的影响

صينى. 为了明确紫花苜蓿对牛角花齿蓟马为害的抗性机理，测定了不同牛角花齿蓟马虫口密度下抗、感蓟马苜蓿无性系R-1、I-1的丙二醛（MDA）含量及防御性酶POD、PPO和PAL活性的变化。结果表明：受牛角花齿蓟马为害后，R-1、I-1无性系的MDA含量均上升，为害第5天时，MDA含量的增加量均与虫口密度呈显著的正相关，且I-1无性系MDA含量的增加量显著高于R-1无性系。R-1无性系的POD、PPO和PAL活性在低虫口密度（1、3头/枝条）下均呈上升趋势，在高虫口密度（5、7头/枝条）下均呈先上升后下降的趋势；I-1无性系的POD和PPO活性均呈先上升后下降的趋势，低虫口密度下PAL活性在为害后期上升，高虫口密度下PAL活性先上升后下降。说明POD、PPO和PAL活性的升高可能是紫花苜蓿对牛角花齿蓟马诱导抗性的一种表现，但R-1无性系对牛角花齿蓟马的抗性高于I-1无性系，在牛角花齿蓟马为害后期其体内POD、PPO和PAL活性仍处于较高水平，所以I-1无性系膜脂过氧化程度也较R-1无性系高，表现为感蓟马。

إنجليزي. MDA content and defensive enzymes (POD, PPO, PAL) activity of resistant and susceptible alfalfa clones R-1 and I-1 growing under different thrips densities were tested to explore resistance mechanism of alfalfa plants to thrips damage. The results indicated that MDA contents for both the 2 clones increased. Significantly positive correlation was found between MDA increment and thrips density on the 5th day of damage. MDA increment in I-1 was significantly higher than that of R-1. For R-1 clone, POD, PPO and PAL activity increased under low thrips densities (1, 3 per branch), while under high densities (5, 7 per branch), they increased firstly and then decreased; POD and PPO activity for I-1 increased firstly and then decreased, while for PAL activity, it presented an increased tendency at the late stage of damage under low thrips densities, and under high densities they increased firstly and then decreased, indicating that the increase in activities for POD, PPO and PAL might be a kind of induced resistance of alfalfa to thrips damage. The activities of the 3 enzymes in R-1 were higher than those in I-1, and similarly, I-1 was with more lipid peroxidation and shown as thrips susceptible.