苜蓿是全世界最重要的豆科牧草。病害是影响苜蓿产量、质量的重要因素，特别是在大面积种植时，病害很容易发生。为防治病害，大量化学农药的使用，造成有害物质在植物体内、水中富集，通过物质循环进入人畜体内，严重污染了农产品和环境，危害了人体和畜禽健康。植物源农药以其对病原菌不易产生抗药性、在空气和土壤中易分解、无残留等特性，具有广泛的研究与开发价值和应用前景。植物源农药的物质基础是植物次生代谢产物。然而，有些植物次生代谢物在健康植物中含量很低，而在植物受到病原菌的侵染时会大量增加。这些物质是植物在受到病原物的侵染时作出的生理应激反应而产生的应激物质，会对病原菌起到抵抗作用。本课题旨在对感染褐斑病和白粉病的苜蓿次生代谢物进行系统地研究，探寻苜蓿在抵抗病原菌侵染时产生的具有抑制病原菌生长的应激次生代谢物，发现植物源农药先导化合物，为开发植物源农药奠定物质基础。

Alfalfa (Medicago sativa) is an important forage worldwide. Alfalfa disease is the one of major factors which affects the yield, quality and the sustainable development of Alfalfa，especially in large-scale cultivation. The use of large number of chemical pesticides for the disease prevention and control results in enrichment of harmful substances in plants, water, animal body and human body through the circulation of materials, and pollutions of the agricultural products and the environment. Since pathogen is not easy to produce drug-resistant to botanical pesticides, and botanical pesticides are easily decomposed in the air and soil, botanical pesticides has broad prospect of application. Secondary metabolites are the material basis of botanical pesticides. However, the contents of some plant secondary metabolites are low in healthy plants, but high in the pathogen-infected plants. These secondary metabolites are stress substance that plants produce to resist the infections of pathogens. This project aims at finding the stress-secondary metabolites and lead compounds which can resist the infections of pathogens from Pseudopeziza medicaginis and Leveillula leguminosarum-infected Alfalfa，and establishing the meterial basis for the development of botanical pesticides.