小麦蚕豆间作调控蚕豆枯萎病抗性的生理与分子机制

Fusarium wilt of faba bean is one of the most widespread and destructive soil-borne fungal diseases because of continuous monocropping, which has severely reduced yield, quality and limited faba bean production. Nowadays it is difficult to control the disease by conventional chemical control strategies in field production. Intercropping systems have a long history in crop production in China, and have widely accepted as a sustainable practice due to its yield advantage and disease suppression. Recently years, the mechanisms by which intercropping control crop soil-borne diseases were mainly focused on the inhibition effects of rhizosphere microbial diversity and root exudates on pathogen, little information is known about resistance changes of host crops in intercropping system, especially no literatures have confirmed the change of host crop resistance under autotoxic substances and pathogen stress in intercropping system. Our previous studies have demonstrated that pathogen growth were promoted by autotoxic substances of phenolic acid secreted by the root of faba bean, thus promoting occurrence of Fusarium wilt, whereas the Fusarium wilt was suppressed when wheat intercropped with faba bean. Further studies indicated that autotoxic substances could increase the pathogenicity of pathogen and reduce the disease resistance of host crops. In order to elucidate the interspecific interaction mechanism of agro-biodiversity managing crop diseases, based on the studying of crop diseases managed and increasing production in the wheat and faba bean intercropping system, the objectives of this study are to find out that if the resistance of faba bean could be enhanced by wheat and faba bean intercropping under autotoxic substances and pathogen stress, using proteomics analysis and physiology methods, to reveal the mechanisms of wheat and faba bean intercropping control faba bean Fusarium wilt on the level of physiology and molecule. The results of this study will help to establish the theory foundation for using biodiversity as means to increase crop yield, improve disease control and achieve agricultural sustainable development. The results also provide an experiment evidences for developing an ecologically sound strategies, economical and effective approach to control the soil-borne disease caused by crop continuous cultivation.

蚕豆连作导致土传枯萎病普遍发生，严重制约了我国的蚕豆生产，目前生产中尚无有效的化学防治措施。合理间作不仅能显著增加作物产量，而且是控制土传病害的有效措施。长期以来，间作控制土传病害的研究主要集中在根际微生物和根系分泌物对病原菌的抑制方面，对间作系统寄主作物抗病性的关注较少，尤其是连作自毒物质和病原菌协同作用下作物抗病性的变化及其对土传病害发生影响及作用机制尚缺乏系统研究。我们的前期研究表明，蚕豆根系分泌的自毒物质能促进病原菌生长，加剧枯萎病发生，而小麦蚕豆间作控制了蚕豆枯萎病发生。最近研究显示，自毒物质通过增强病原菌的致病力并降低作物的抗病性。因此，本项目拟以小麦蚕豆间作体系为研究对象，通过水培、土培试验和蛋白质组学技术，研究自毒物质和病原菌胁迫下间作调控蚕豆枯萎病抗性的机理，揭示间作控制土传病害的生理与分子机制，为应用生物多样性持续控制作物病害，提高产量，实现农业可持续发展提供理论依据。

高投入和高产出、高产品种大面积单一连作为特点的集约化种植已成为我国重要的农业生产模式，这一模式的不断推广与发展造成作物土传病害在我国的蔓延和流行。多年来，研究者从病原菌的稀释效应、根系物理阻隔抑制病原菌传播方面开展了系统研究，但有关自毒物质和病原菌胁迫下间作对寄主作物抗病性的影响及作用机理的研究还未系统报道。本项目通过水培、田间试验、病原菌接种和自毒物质外源添加等手段，研究自毒物质对尖孢镰刀菌产酶和产毒的影响，从蚕豆组织结构抗性、生理生化抗性和蛋白质差异表达角度阐明间作提高蚕豆枯萎病抗性的生理与分子机制。研究表明，自毒物质（肉桂酸和苯甲酸）能促进镰刀菌产酶（果胶酶、纤维素酶、蛋白酶和淀粉酶）及产毒（枯萎酸，FA），且具有浓度效应。自毒物质（苯甲酸和肉桂酸）和尖孢镰刀菌协同增加蚕豆FA含量，蚕豆根、茎中细胞壁降解酶（CWDEs）活性提高，根系和茎中木质素含量增加。蚕豆根系过氧化程度（H2O2、O2-和MDA）含量增加，抗氧化酶（SOD、PAL和PPO）活性降低，抗性物质（总酚、类黄酮和可溶性糖）和营养元素（N、P、K、Mn）含量减少，光合作用减弱（净光合速率、蒸腾速率、气孔导度，胞间CO2）。蚕豆根系超微结构观察表明：酚酸和尖孢镰刀菌协同干扰了根系细胞功能，且主要细胞器随处理浓度增加而消解，而间作有效抑制CWDEs活性，使蚕豆根茎细胞壁更加完整，促进根茎木质素的分泌，减少根茎中胼胝质的沉积。间作提高抗氧化酶活性、抗性物质和营养元素含量，降低蚕豆根系过氧化程度。间作上调表达能量、细胞完整性、抗病和细胞氧化还原平衡功能的蛋白，增加蚕豆能量供应，及时清除自由基，进一步合成茉莉酸和乙烯促进蚕豆根系中抗坏血酸－谷胱甘肽循环，激活蚕豆抗病系统实现持续抗病。本研究结果可为进一步深入揭示应用间作缓解作物土传病害高发，提高作物产量，实现农业可持续发展提供科学依据。