Salicylic acid has allelopathy, but wheat and faba bean intercropping can alleviate faba bean fusarium wilt under salicylic acid stress.

Background: The goals of this study were to evaluate the role of salicylic acid in the continuous cropping obstacle of faba bean ( Vicia faba L.) and explore how intercropping with wheat alleviates these obstacles. We designed a hydroponic pot experiment to study the effects of exogenous salicylic acid on the occurrence of Fusarium wilt, seedling growth, physiological resistance of faba bean and pathogenicity of Fusarium oxysporum f. sp. fabae (FOF). Results: The results showed that salicylic acid significantly increased the incidence and disease index of faba bean, inhibited the growth of seedlings and reduced the physiological resistance of faba bean. An in vitro study of FOF found that salicylic acid increased the ability of the organism to produce fusaric acid, cellulase and pectinase, which increased the susceptibility of faba bean to Fusarium wilt. Interestingly, intercropping with wheat significantly reduced the exudation of salicylic acid from the faba bean root system, which directly reduced the deleterious effects of salicylic acid. Alternatively, intercropping also increased the ability of faba bean to defend itself from the aspect of physiological resistance and indirectly reduced the autotoxicity of salicylic acid. Conclusions: In conclusion, we found that salicylic acid, as an autotoxic substance, deleteriously affected the growth of faba bean, but intercropping with wheat could alleviate its autotoxicity. This finding suggests the existence of an important mechanism in which intercropping alleviates the obstacles in continuous cropping and controls Fusarium wilt.