[Microbial and physiological mechanisms for alleviating fusarium wilt of faba bean in intercropping system.]

A field trial was conducted to investigate effects of wheat and faba bean intercropping on incidence and index of fusarium wilt, amount of Fusarium oxysporum of faba bean, oxidase activity and membrane peroxidation of faba bean roots. Functional diversity of microbial community in rhizosphere soil of faba bean was analyzed by using Biolog microbial analysis system, contents of pheno-lic acids in faba bean rhizosphere soil were determined with high performance liquid chromatography (HPLC). Results showed that in comparison with that of monocropped faba bean, wheat and faba bean intercropping tended to reduce the incidence and disease index of faba bean. The fusarium wilt was significantly decreased by 15.8% and 22.8% during the peak infection and late infection stages, and the average well color development (AWCD value) was promoted obviously. The Shannon diversity (H) and richness (S) increased by 4.4% and 19.4% during the peak infection stage and 5.3% and 37.1% during the late infection stage, respectively. Principal component analysis demonstrated that intercropping significantly changed the rhizospheric microbial community composition. The amount of F. oxysporum in rhizosphere soil of intercropped faba bean was significantly decreased by 53.8% and 33.1%, respectively, during the peak infection and late infection stages, and contents of 4-hydroxy benzoic acid, vanillic acid, syringic acid, ferulic acid, benzoic acid and cinnamic acid also significantly decreased, peroxidase (POD), catalases (CAT) activities in roots of intercropped faba bean increased significantly by 20.0% and 31.3%, respectively during the peak infection stage and 38.5% and 66.7% respectively during the late infection stage, and the malondialdehyd (MDA) content decreased significantly by 36.3% and 46.3%, respectively during peak infection stage and late infection stage. It was concluded that wheat with faba bean intercropping could significantly promote the soil microbial activity and diversity, reduce the accumulation of phenolic allelochemicals and the amount of F. oxysporum in rhizosphere soil, increase the activities of CAT and POD, reduce MDA content in roots, and thus promote the resistance of faba bean to F. oxysporum infection.