Faba Bean–Wheat Intercropping Can Control the Occurrence of Faba Bean Fusarium Wilt by Alleviating the Inhibitory Effect of Benzoic Acid on Disease Resistance Metabolism and the Expression of Resistance Genes

Background: Continuous cropping leads to the accumulation of autotoxic substances in faba beans, which limits their global production. Intercropping is widely used to alleviate these problems. Aim: This study aims to explore the important role of Fusarium oxysporum f. sp. fabae (FOF) and benzoic acid stress in enhancing the occurrence of faba bean Fusarium wilt and the potential mechanism of faba bean-wheat intercropping to control the occurrence of this disease. Methods: We analyzed the pathogenic mechanism of FOF and benzoic acid and the defense response of faba bean-wheat intercropping against the autotoxicity of benzoic acid under hydroponic conditions that included the pathogen alone and in combination with different concentrations of benzoic acid. Results: The dual stress of FOF and benzoic acid inhibited the activity of defensive enzymes, the synthesis of defensive substances, and the expression of defensive genes in faba bean roots and reduced the disease resistance of faba bean. This shows that benzoic acid plays an important role in helping FOF cause disease. Faba bean-wheat intercropping improves plant resistance by alleviating benzoic acid stress and reducing the incidence and disease index of Fusarium wilt. Conclusion: The dual stress of FOF and benzoic acid promotes the occurrence of faba bean Fusarium wilt by destroying the root defense system of faba bean. Faba bean-wheat intercropping can effectively alleviate the autotoxicity of benzoic acid and control the occurrence of Fusarium wilt by improving the physiological and biochemical resistance of faba beans and the expression of defense genes.