Intercropping alleviated the phytotoxic effects of cinnamic acid on the root cell wall structural resistance of faba bean and reduced the occurrence of Fusarium wilt

Abstract

Soilborne Fusarium wilt is a key factor restricting the cultivation of faba bean. Intercropping faba bean and wheat effectively alleviate faba bean Fusarium wilt. This study analyzed the mechanism by which cinnamic acid promotes Fusarium wilt and the mechanism that enables intercropping alleviated Fusarium wilt. Faba beans were inoculated with Fusarium oxysporum f. sp. fabae (FOF), while the controls were not inoculated. Different concentrations of cinnamic acid were added to the inoculated plants to study the occurrence of Fusarium wilt, seedling growth, the activities of cell wall degradation enzyme (CWDESs) produced by FOF in the root, defense enzymes, total phenolics and lignin, levels of expression of the pathogenesis‐related genes (PRs) PR1, PR2, and PR10, and changes in the submicroscopic cell wall structure of the roots under monocropping and intercropping systems. Cinnamic acid increased the activities of CWDEs produced by FOF in the roots, increased the activities of phenylalanine ammonia lyase and polyphenol oxidase and the contents of total phenolics and lignin, and upregulated the levels of expression of PRs in the root, but it decreased the activity of peroxidase. Transmission electron microscopy (TEM) observations identified severe damage and disruption of the root cell walls, and numerous FOF mycelia entered the cytoplasm from the cell wall. The combination of these factors increased the occurrence of Fusarium wilt. The activities of CWDEs produced by FOF in the roots decreased by intercropping wheat with faba bean, which increased the resistance of the root cell walls to infection and decreased the Fusarium wilt.

Promotion of faba bean seedling growth under Fusarium oxysporum f. sp. fabae and cinnamic acid stress in faba bean‐wheat intercropping system and underlying proteomic mechanisms

“…In the present study, a comparison of monocropping and FOF inoculation (M + F) with the M + F + C group showed the upregulation of six proteins in the latter, which were found to be mostly involved in carbohydrate metabolism and energy‐associated and cytoplasmic functions. In our previous study, we found that exogenous cinnamic acid treatment adversely affected structural resistance in the cell walls of faba bean roots (Yang et al, 2022b). These findings suggest that when faba bean was subjected to a single stress (FOF), proteins associated with energy metabolism, antioxidant function, and the catabolism of hydrogen peroxide were upregulated, and faba bean initiated its own defense response to accelerate energy generation to stress resistance.…”

“…Cinnamic acid is known to be an autotoxic phenolic acid. Zheng et al (2022) observed high cinnamic acid concentrations in the rhizosphere soils of faba bean, while Yang et al (2022b) observed that FOF inoculation together with cinnamic acid treatment reduced seedling growth. Here, the M + F + C group showed greater growth inhibition compared with the M + F group.…”

“…observed high cinnamic acid concentrations in the rhizosphere soils of faba bean, whileYang et al (2022b) observed that FOF inoculation together with cinnamic acid treatment reduced seedling growth.…”

“…Niveum (FON), while Ye et al (2004) observed growth inhibition of cucumber leaves by cinnamic acid root exudates. Exogenous addition of cinnamic acid was also found to reduce faba bean growth (Yang et al, 2022b). These findings indicate that cinnamic acid enhances Fusarium oxysporum infection and inhibits crop growth.…”

“…It was also found that intercropping reduced the deleterious effects of 100 mg L −1 cinnamic acid on plant growth and that this concentration was most effective for controlling wilt. Therefore, we chose a cinnamic acid concentration of 100 mg L −1 for our study (Guo et al, 2020a; Yang et al, 2022b). Here, we aimed to identify root proteins in faba bean that were associated with alleviating FOF‐ and cinnamic acid‐induced growth inhibition under faba bean‐wheat intercropping.…”