Benzoic acid promotes Fusarium wilt incidence by enhancing susceptibility and reducing photosynthesis of faba bean

Continuous faba bean (Vicia faba L.) cropping causes adverse effects, including increased secretion of autotoxic substances (benzoic acid) and incidence of diseases (Fusarium wilt). Fusarium commune infects faba bean seedlings and is treated with different benzoic acid concentrations. Therefore, this investigation analysed the association of benzoic acid with faba bean wilt incidence and the mechanisms involved. Furthermore, seedling growth, tissue structure, Fusarium wilt incidence, cell wall degrading enzymes (CWDEs) activity, lignin levels, and leaf photosynthetic parameters were assessed. The results indicated that fungal infection markedly reduced biomass and photosynthesis in the faba bean. Microscopic analysis showed slightly thickened stems' xylem vessels. Benzoic acid treatment with F. commune infection substantially increased F. commune-mediated CWDEs activity in the faba bean stem and lignin level but reduced photosynthesis and biomass, elevating Fusarium wilt incidence. Furthermore, broken tissues, xylem thickening, and stem cavities were observed. The investigation indicated that benzoic acid treatment and F. commune infection-induced stem lignin might be a resistance response; however, increased pathogenicity and reduced photosynthesis enhanced susceptibility and aggravated Fusarium wilt.