In this study, we investigated the effects of volatile organic compounds (VOCs) produced by endophytic bacteria belonging to the Bacillus genus on the virulence traits of Ralstonia solanacearum R32, the causal agent of potato bacterial wilt disease. The results of gas chromatography-mass spectrometry analysis showed that strains B. safensis Har267, B. pumilus Fer469, B. zhangzhouensis Kh690, B. aerius Kh867, and B. wiedmannii Ah945 able to produce 10, 4, 18, 6, and 12 VOCs with high quality, respectively. All endophytic bacteria produced VOCs that significantly reduced wilting symptoms in planta, inhibited the cell population of R. solanacearum R32 in vitro, and reduced the cell population both in the shoots and roots of inoculated plants at different levels. The VOCs significantly reduced the attachment of R. solanacearum R32cells to root tissues of potato plants, as well as chemotaxis motility towards root extract. Our results revealed that VOCs could reduce swarming-, swimming-, twitching motility, and biofilm formation by R. solanacearum R32 which are important for pathogenicity. Scanning electron microscopy analysis revealed various morphological abnormalities in the R. solanacearum R32 cells exposed to the VOCs produced by B. safensis Har267 and B. aerius Kh867 strains. Results presented in this study showed that the VOCs produced by endophytic bacteria investigated can reduce bacterial wilt disease. Investigation of the mechanisms of biocontrol activities increases our knowledge to design better methods to control bacterial pathogens.
