Proteomic analysis of the faba bean-wheat intercropping system in controlling the occurrence of faba bean fusarium wilt due to stress caused by Fusarium oxysporum f. sp. fabae and benzoic acid
Authors: Hu Bijie , Zheng Yiran , Lv Jiaxing , Zhang Jing , Dong Yan 
Published: October 2023

Abstract
Background
In faba bean, continuous cropping severely affects plant growth and increases the incidence of fusarium wilt due to the accumulation of pathogens and autotoxic substances. The intercropping of faba bean and wheat is commonly used to alleviate the occurrence of fusarium wilt in the faba bean.

Objective
To investigate the role of Fusarium oxysporum f. sp. Fabae(FOF) and benzoic acid in the occurrence of faba bean fusarium wilt and unravel the potential mechanism of intercropping in alleviating its occurrence.

Methods
Hydroponic experiment was carried out using monocropping faba bean (M) and intercropping faba bean and wheat (I) patterns under FOF alone stress (M + F, I + F), FOF and benzoic acid double stress (M + F + B, I + F + B). The growth of faba bean seedlings under FOF and benzoic acid dual stresses were analyzed as well as the protein expression profile of monocropping and intercropping faba bean roots.

Result
Under FOF stress, the growth of faba bean seedlings was inhibited, and the inhibitory effect was enhanced under the dual stress of FOF and benzoic acid. However, faba bean-wheat intercropping alleviated the inhibitory effect of FOF and benzoic acid on faba bean growth. In faba bean, the up-regulated protein was involved in different functions, such as redox, hydrogen peroxide decomposition, and metabolic processes under FOF stress (M + F, I + F) compared to the control. Compared with FOF stress (M + F, I + F), under the dual stress of FOF and benzoic acid (M + F + B, I + F + B), the up-regulated protein in faba bean were involved in intracellular redox balance, defense, and maintenance of cell integrity. Compared with monocropping (M, M + F, M + F + B), the up-regulated protein function of intercropping(I, I + F, I + F + B) was mainly involved in the biosynthesis of secondary metabolites, redox balance, biological carbon fixation of photosynthesis, and so on. KEGG enrichment analysis results showed that intercropping increased ethylene and jasmonic acid synthesis and other related pathways to improve resistance against fusarium wilt in the faba bean.

Conclusion
The growth of faba bean was inhibited under FOF stress and the inhibitory effect was enhanced under the dual stress of FOF and benzoic acid, which promoted the occurrence of faba bean fusarium wilt. This might be due to the down-regulation of energy and cytoplasmic matrix proteins under FOF and benzoic acid stress. The faba bean wheat intercropping alleviated the inhibition of FOF and benzoic acid stress by up-regulating the biosynthesis of secondary metabolites, redox homeostasis, photosynthetic carbon fixation, and other related proteins. Besides, it also promoted the biosynthesis of ethylene, and jasmonic acid, improved the resistance of faba bean plants, and alleviated the occurrence of faba bean fusarium wilt. This provides a theoretical basis for the determination of jasmonic acid and ethylene content.