Cinnamic, myristic and fumaric acids in tobacco root exudates induce the infection of plants by Ralstonia solanacearum

Aim The secretion of allelochemicals from plant roots plays a key role in soil sickness and soil-borne disease. The goal of this study was to investigate the role of allelopathic chemicals in Ralstonia solanacearum-infected tobacco roots. Methods The organic acids investigated in the present study are major components of tobacco root exudates. Through a swarming assay, we assessed the chemotaxis and colonization of R. solanacearum in response to organic acids. Results Fumaric acid was detected, and the results showed that this acid could serve as a semiochemical for attracting R. solanacearum and inducing the formation of biofilms of this species. The results also revealed that cinnamic and myristic acids play significant roles on swarming motility and chemotaxis. In addition, cinnamic, myristic and fumaric acids could enhance the expression of chemotaxis- and motility-related genes in R. solanacearum cultured in minimal medium. Furthermore, these three acids promote R. solanacearum colonization and accelerate disease progression in tobacco. Conclusion Cinnamic, myristic and fumaric acids could serve as semiochemical attractants to induce the colonization and infection of R. solanacearum. The results of the present study enhance our understanding of the ecological effects of plant root exudates in plantmicrobe interactions and help to reveal the relationship between tobacco bacterial wilt and the autotoxins and allelochemicals that accumulate from root exudates.