Silicon Controls Bacterial Wilt Disease in Tomato Plants and Inhibits the Virulence-Related Gene Expression of Ralstonia solanacearum

Silicon (Si) has a multifunctional role in improving plant growth and enhancing plant disease resistance, but its mechanisms are not fully understood. In this study, we investigated the impacts of silicon application on the control of bacterial wilt and elucidated the molecular mechanisms using transcriptome sequencing. Compared to non-Si treatment, Si application (0.5–2 mM) significantly reduces tomato bacterial wilt index by 46.31–72.23%. However, Si does not influence the growth of R. solanacearum. Si application negatively influences R. solanacearum exopolysaccharide (EPS) synthesis and biofilm formation. Transcriptome analysis showed that Si treatment significantly downregulates the expression of virulence genes’ transcriptional regulator (xpsR), EPS synthesis-related genes (epsD and tek), and type III effectors (HrpB2, SpaO, and EscR) in R. solanacearum. In addition, Si remarkably upregulates the expression of twitch motor-related genes (pilE2, pilE, fimT, and PilX). These findings suggest that silicon-suppressed tomato wilt incidence may be due to the regulation of the virulence-related genes of R. solanacearum by Si. Our research adds new knowledge to the application of Si in the field of disease control.