Rhizosphere reactive oxygen species as a protective barrier suppress Fusarium oxysporum invasion in tomato

Abstract

As the threat posed by soil-borne pathogenic fungi is increasingly severe, developing green pest control technologies is essential for sustainable agriculture. Here we investigated the formation of rhizosphere reactive oxygen species in tomato under the infection by the fungi Fusarium oxysporum f. sp. lycopersici, and evaluated their effects on Fusarium activity. Results show that, following Fusarium infection, tomato enhanced the production of hydrogen peroxide, H₂O₂, and hydroxyl radical, ^•OH , in the rhizosphere, up to 603.23 and 0.63 µmol kg^− 1 at 10- and 20-days post-inoculation, respectively. Random forest analysis, sterilization experiments, and in vitro microbial incubation experiments demonstrated that, under infection, microbial factors contributed more strongly to rhizosphere oxygen species production than the measured abiotic factors, including Fe(II) and water-soluble phenols. ROS quenching and H₂O₂ addition experiments suggested that H₂O₂ exhibited stronger suppressive effects on Fusarium than ^•OH, which decreased Fusarium abundance by 42.11−60.54%. Scanning electron microscopy, propidium iodide staining, and extracellular conductivity measurements further revealed that rhizosphere H₂O₂ suppressed Fusarium growth mainly by damaging hyphal membranes and causing ion leakage. These findings reveal a widespread but previously unrecognized inhibitory effect of rhizosphere reactive oxygen species on Fusarium, which may represent a promising strategy for green pest control.