The inhibitory effects of different types of Brassica seed meals on the virulence of Ralstonia solanacearum

BACKGROUND Understanding the specific inhibitory effects of different Brassica seed meals (BSMs) on soilborne pathogens is important for their application as biocontrol agents for controlling plant disease. In this study, the seed meals of Brassica napus L. (BnSM), Brassica campestris L. (BcSM), and Brassica juncea L. (BjSM), and the combined seed meal of BcSM and BjSM (CSM, 1:1), were selected for investigation. The inhibitory effects of these seed meals on the plant pathogen Ralstonia solanacearum (Smith) and tomato bacterial wilt, were assessed and compared. RESULTS All the BSMs significantly inhibited the growth of R. solanacearum in vitro. Furthermore, the BSMs could effectively suppress R. solanacearum virulence traits, including motility, exopolysaccharide production, dehydrogenase activity, virulence-related gene expression, and colonization in the soil. Among them, BjSM showed the best inhibiting effects, and CSM displayed synergic toxicity against R. solanacearum. In addition, the predominant antibacterial compounds in BcSM and BjSM were identified as the volatile compounds, 3-butenyl isothiocyanate and allyl isothiocyanate, respectively. Finally, pot experiment verified that the control effects of BjSM and CSM on tomato wilt reached more than 90%. CONCLUSION This is the first study to report on the ability of different kinds of BSMs to suppress the virulence of R. solanacearum and biocontrol efficiencies against bacterial wilt in tomato plants. Furtherly, the main antibacterial compounds in the BSMs were identified. The results demonstrated that CSM may possess potential for controlling bacterial wilt caused by R. solanacearum. The results provide a fresh perspective for comprehending the mechanism underlying BSM suppression of pathogens and plant disease.

Automated summary

This study investigated the inhibitory effects of different Brassica seed meals on the pathogen Ralstonia solanacearum and bacterial wilt in tomatoes. It was found that Brassica juncea seed meal exhibited the best inhibiting effects, while the combined seed meal of Brassica campestris and Brassica juncea showed synergic toxicity against R. solanacearum. Additionally, volatile compounds from Brassica campestris and Brassica juncea were identified as the predominant antibacterial compounds. Pot experiments confirmed that Brassica juncea seed meal and the combined seed meal were highly effective in controlling tomato wilt. The study provides insights into the mechanisms of Brassica seed meal suppression of pathogens and plant disease.