Antibacterial Activity of Ferulic Acid Ester against Ralstonia solanacearum and Its Synergy with Essential Oils

Ralstonia solanacearumis one of the ten most harmful plant bacteria worldwide, and traditional agrochemicals are not very effective in controlling this pathogen. Moreover, excessive pesticides always bring organic residues and resistant strains, which cause the unsustainability of the environment. In this paper, ferulic acid and essential oils are used as antibacterial materials. These compounds are natural substances with low toxicity and environmental safety. Through the structural optimization and the analysis of binary combined bacteriostatic efficiency, the MIC values of chlorobutyl ferulate (2e) and peppermint essential oil (EO1) were 0.64 mg/mL and 2.02 mg/mL, respectively, and the MIC value of2e-EO1(mass ratio 1:1.5) was 0.40 mg/mL. The growth rate of bacteria treated with2e-EO1was inhibited, the OD590nmvalue of cell membrane decreased by 57.83%, and the expression levels ofhrpB,pehC,pilT,polA,aceE,egl, andphcAwere downregulated to 18.81%, 30.50%, 14.00%, 44.90%, 86.79%, 23.90%, and 27.56%, respectively. The results showed that2e-EO1had a synergistic inhibitory effect againstR. solanacearum. It significantly affected the formation of the bacterial cell membrane and the expression of pathogenic genes. Consequently,2e-EO1provides the potential to become a green pesticide and can promote the sustainability of the agricultural ecological environment.Keywords:Ralstonia solanacearum;ferulic acid;essential oil;antibacterial activity;synergistic effect;pathogenic gene