Ozone treatments activate defence responses against Meloidogyne incognita and Tomato spotted wilt virus in tomato.

Background: Ozonated water (O wat) soil drench and/or foliar spray applications were evaluated for their potential to control the root-knot nematode Meloidogyne incognita (RKN) and the airborne pathogen Tomato spotted wilt virus (TSWV) in tomato. We investigated how O wat modulates the salicylic acid/jasmonic acid/ethylene (SA/JA/ET) signalling network in the host, locally and systemically, to induce resistance to nematode and virus.

Results: The application as soil drench was effective in reducing the number of galls and egg masses, but did not reduce the incidence and severity of TSWV infection. Conversely, O wat applied by foliar spray decreased TSWV disease incidence and severity (-20%), but was not able to control M. incognita infection. SA-related genes were generally upregulated in both locally treated and systemically reached tissues, showing a positive action of the O wat treatment on SA signalling. Neither O wat application method significantly altered JA-related gene expression in either direction. ET-related genes were differentially regulated by root or leaf treatments, indicating that O wat may have different effects on ET-mediated signalling in different organs. JA/ET/SA related pathways were differentially modulated by O wat in the presence of either RKN or TSWV.

Conclusion: O wat had a higher efficacy when applied directly to organs challenged by the pathogens, although it was potentially able to stimulate defence responses through the activation of SA signalling. Owing to its safety and effectiveness in controlling nematode and virus infections, O wat can be considered as a possible alternative tool for sustainable disease management practices. © 2019 Society of Chemical Industry.