粘质沙雷氏菌引起褐飞虱回避行为的化学机制研究

Pathogenic microorganisms are important components of natural control and biological control of insect pests. Interspecies chemical communication plays an important role in insect-plant-parasitoid tritrophic interactions, but little is known about the chemical communication between insect and pathogen interactions. In previous studies, we isolated and identified a novel entomopathogenic Serratia marcescens strain S-JS1 from diseased Nilaparvata lugens from rice paddy fields, and found that the S. marcescens strain S-JS1 can induce N. lugens avoidance behavior. Therefore, methods will be applied in this program, such as SPME (solid phase micro-extraction), GC-MS (gas chromatography-mass spectrometry), GC-EAD (GC-electroantennogram detection), EAG (electroantennography) and EPG (electrical penetration graph). Analysis and identification of volatile semiochemicals composition and content in S. marcescens, S. marcescens-induced rice and N. lugens, whether these chemicals create a significant avoidance behavior in N. lugens will be determined, the active ingredients will be identified based on the characteristics of insect avoidance behavior. Pot and field plot experiments to verify the actual effectiveness of them on repelling N. lugens. Then by combining a series of chemical, electrophysiological and behavioral analyses, we intend to elucidate the chemical mechanism of entomopathogenic S. marcescens induced avoidance behavior in N. lugens. The results of this project are important not only for expanding theoretical basis of chemical communication among entomopathogen, insect and plant, but also providing practical basis for the effective biological control of N. lugens.

病原微生物是害虫自然控制和生物防治的重要组成部分。虽然种间化学信息联系在昆虫-植物-寄生蜂三级营养系统中起重要作用，但有关昆虫-病原微生物间的化学信息联系还知之甚少。在前期研究中，项目组从稻田感病褐飞虱中分离获得粘质沙雷氏菌Serratia marcescens S-JS1新株系，并发现该病菌能导致褐飞虱回避行为反应。为此，我们拟采用SPME、GC-EAD、GC-MS、EAG和EPG等技术，分析鉴定粘质沙雷氏菌及其诱导水稻和褐飞虱产生的挥发性信息化合物组分与含量，测定褐飞虱对其的回避行为反应，明确对褐飞虱具驱避作用的高活性信息化合物成分，盆栽和小区实验验证其驱避褐飞虱的有效性，阐明昆虫致病细菌粘质沙雷氏菌引起褐飞虱回避行为的化学机制。研究结果不仅丰富昆虫病原微生物-昆虫-植物间化学信息联系的理论基础，而且可为褐飞虱的有效生物防治提供实践依据。

病原微生物是害虫自然控制和生物防治的重要组成部分。在长期的协同进化中，昆虫具备了识别昆虫病原微生物的能力，进而做出相应的防御行为反应，然而有关致病菌引起寄主昆虫行为反应的内在机制所知甚少。褐飞虱属半翅目飞虱科，是我国和许多亚洲国家当前水稻上的首要害虫。因此，本文以褐飞虱为对象，在获得其致病菌粘质沙雷氏菌Serratia marcescens S-JS1的基础上，采用SPME、溶剂浸提、GC-MS、Y型嗅觉仪等技术，研究了粘质沙雷氏菌介导的褐飞虱的行为反应，进行了相应化合物分析，探索了粘质沙雷氏菌的应用。结果表明，粘质沙雷氏菌S-JS1对褐飞虱若虫和成虫均具有杀虫活性；粘质沙雷氏菌、菌处理水稻和感菌褐飞虱均可引起的褐飞虱若虫和雌雄成虫趋避行为反应；菌提取物对褐飞虱具有杀虫活性，处理后24h，LC50为0.45mg/ml；处理后48h， LC50为0.38mg/ml；褐飞虱3龄若虫和雌雄成虫均对浓度为0.5mg/ml的菌提取物处理的水稻具有趋避行为；菌处理水稻后，挥发物长叶烯量增加；褐飞虱感菌后，挥发物的数量减少；褐飞虱3龄若虫对感菌褐飞虱提取物具有趋避行为反应。粘质沙雷氏菌分别与螺虫乙酯、噻虫嗪混用，对褐飞虱3龄若虫的致死率，有叠加和协同增效作用，未发现拮抗作用。菌药混用时褐飞虱的死亡率显著高于单用粘质沙雷氏菌和相同浓度的杀虫剂。在109cfu/ml粘质沙雷氏菌与20mg/L螺虫乙酯混用时，对褐飞虱的致死率为80.5%，表现出增效作用。菌药混用既可提高粘质沙雷氏菌的防效，也可减少杀虫剂的使用。因此，本研究结果不仅丰富昆虫病原微生物-昆虫-植物间化学信息联系的理论基础，而且可为褐飞虱的生物防治提供实践依据。