Cinnamic Acid Increased the Incidence of Fusarium Wilt by Increasing the Pathogenicity of Fusarium oxysporum and Reducing the Physiological and Biochemical Resistance of Faba Bean, Which Was Alleviated by Intercropping With Wheat

BACKGROUND

Continuous cropping has resulted in the accumulation of self-toxic substances in faba beans which has restricted their global production. Intercropping is widely used to alleviate these problems.

AIMS

To explore the role of cinnamic acid stress in faba bean physiology and disease resistance, and the potential mitigating effects of intercropping the faba bean with wheat.

METHODS

Faba bean seedlings were grown with or without wheat in both field and hydroponic conditions in the presence of different cinnamic acid concentrations and Fusarium oxysporum (FOF), the occurrence of. Fusarium-mediated wilt and oxidative stress, as well as plant growth indices and the anti-pathogen defense system were analyzed.

RESULTS

Cinnamic acid significantly increased Fusarium pathogenicity, inhibited the activity of defense enzymes and reduced the ability of plants to resist pathogens, indicating the importance of cinnamic acid in the promotion of Fusarium wilt resulting in reduced seedling growth. Intercropping with wheat improved plant resistance by alleviating cinnamic acid-induced stress, which promoted crop growth and decreased the incidence and disease index of Fusarium wilt.

CONCLUSION

Cinnamic acid promotes Fusarium wilt by stimulating pathogen enzyme production and destroying the defense capability of faba bean roots. Intercropping reduces Fusarium wilt by alleviating the damage caused by cinnamic acid to the defense system of the faba bean root system.

[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.