营养期与繁殖期紫花苜蓿营养代谢变化及其对苜蓿斑蚜适合度的影响

Nutritional metabolic changes in Medicago sativa during vegetative and reproductive stages and their effects on the fitness of spotted alfalfa aphid Therioaphis trifolii

中文关键词:紫花苜蓿  苜蓿斑蚜  生育期  生命表  营养物质  基因表达  生态调控

keywords:Medicago sativa  Therioaphis trifolii  developmental stage  life table  nutrient  gene expression  ecological regulation

中文摘要:为探究寄主植物生育期调控苜蓿斑蚜Therioaphis trifolii种群适合度的内在机制，该研究系统比较紫花苜蓿Medicago sativa营养生长期与繁殖期的营养差异及其对苜蓿斑蚜种群增长、体内营养物质及代谢基因表达的影响。结果表明：与营养生长期相比，繁殖期紫花苜蓿中粗蛋白含量、可溶性糖含量和粗脂肪含量显著降低，而结构性抗性物质中性洗涤纤维、酸性洗涤纤维含量和抗性物质总皂苷含量显著升高。与取食营养生长期紫花苜蓿的苜蓿斑蚜相比，取食繁殖期紫花苜蓿的苜蓿斑蚜种群的内禀增长率、净增殖率和周限增长率均显著降低，若虫发育历期显著延长，成虫存活率峰值降低，体内总蛋白、总脂肪、糖原和海藻糖的含量均显著降低，且海藻糖酶基因、脂肪酸合成酶基因及氨基酸转运蛋白基因的相对表达量显著降低。表明繁殖期紫花苜蓿通过营养匮乏与抗性增强双重胁迫，在分子、生理及种群水平上抑制苜蓿斑蚜的适合度。生产中常规的频繁刈割会使紫花苜蓿长期处于营养生长期，反而有助于蚜虫繁殖。

Abstract:To explore the mechanisms underlying the regulaiton of the fitness of the spotted alfalfa aphid Therioaphis trifolii, in host plant developmental stage, the nutritional differences between the vegetative-and reproductive-stage, alfalfa Medicago sativa and their effects on aphid population growth, body nutrient contents, and the expression of metabolic genes were systematically compared. The results indicated that, compared with the vegetative stage, reproductive-stage alfalfa exhibited significantly reduced contents of crude protein, soluble sugar, and crude fat, but significantly higher contents of neutral detergent fiber, acid detergent fiber, and total saponin. Compared with aphids feeding on vegetable-stage alfalfa, aphids feeding on reproductive-stage alfalfa showed significantly lower intrinsic rate of increase, net reproductive rate, and finite rate of increase, significantly prolonged nymphal developmental duration, and a reduced peak adult survival rate. In addition, the contents of total protein, total fat, glycogen, and trehalose, in aphids were significantly decreased, and the relative expression levels of trehalase, fatty acid synthase, and amino acid transporter genes were significantly downregulated. These findings indicate that the reproductive-stage alfalfa suppresses the fitness of T. trifolii, at the molecular, physiological, and population levels through the combined effects of nutritional deficiency and enhanced resistance. Frequent mowing in alfalfa production maintains plants in the vegetative stage for extended period and may consequently promote aphid population growth.