Suppression of tomato bacterial wilt by anaerobic soil disinfestation and associations with production of antagonistic compounds

Background Anaerobic soil disinfestation (ASD) has been proven to be an effective and environmentally friendly method for controlling soil-borne plant diseases. Mechanisms of ASD-mediated pathogen suppression are not fully elucidated but appear to depend on the carbon (C) sources used and involve a combination of abiotic and biotic factors. This study sought to assess the impacts of ASD with different C sources on soil chemical properties, microbial activity, and antagonistic compounds, and identify the major factor(s) driving suppression of tomato bacterial wilt caused by Ralstonia solanacearum. Methods A pot experiment was conducted containing five treatments, i.e., untreated control (CK), anaerobic treatment without C source (ASD-CK), anaerobic treatment with rice bran (ASD-R), wheat bran (ASD-W) and peanut bran (ASD-P). Results All the ASD treatments significantly reduced disease incidence by 83-100% and simultaneously promoted tomato growth, while anaerobic treatments with C sources achieved a better effect than anaerobic treatment alone. This could be associated with the improved soil chemical (lowered Eh, NO3-, SO42- and elevated pH) and biological (elevated dehydrogenase and urease activities) properties and elevated production of antagonistic compounds (Fe2+, Mn2+, citric acid, succinic acid, and ammonia) by anaerobic treatments with C sources. Redundancy analysis further indicated that the elevated ammonia (11.1%, P = 0.002), Mn2+ (5.3%, P = 0.002), citric acid (1.8%, P = 0.046) and urease activity (1.0%, P = 0.036) were the major factors driving disease suppression, which all achieved the highest value in ASD-P. Conclusions In summary, the incorporation of organic materials that improve antagonistic compounds (especially ammonia) production could induce higher inhibition effect against tomato bacterial wilt during the ASD process.