Effects of Ozonation on the Viability of Fusarium Oxysporum Conidia in Hydroponic Nutrient Solutions

ABSTRACT

An ozonation study was conducted for inactivating Fusarium oxysporum, which causes Fusarium wilt, the most serious soil-borne disease in hydroponic cultivation systems. Samples of conidial suspensions of F. oxysporum were treated with ozone gas generated at two ozone gas-phase compositions: oxygen feed and air feed. Oxygen feed ozonation resulted in 0% viability of the pathogen for all ozone dosages tested, including the lowest measurable ozone dosage of 1 mgO₃/L. For air feed ozonation, multiple regression with the Akaike information criterion (AIC) for model selection was used to find the effects of the ozone dosage ${\mathrm{O}}_3$ (mgO₃/L) and the duration of ozonation (time), ${\mathrm{O}}_3$ (min), on the viability (%) of the pathogen at 5 °C and 21 °C. At 5 °C, the viability was found to be linear in ${\mathrm{O}}_3$; at 21 °C, the viability was linear in ${\mathrm{O}}_3$ and quadratic in ${\mathrm{O}}_3$, and the interaction of ${\mathrm{O}}_3$ and ${\mathrm{O}}_3$ was also found to be significant.

The novelty of this study was to use oxygen as feed gas for ozonation for disinfestation of Fusarium oxysporum. This is a significantly different approach from any previously published work on fungal plant pathogen disinfestation. Ozonation with air feed was effective only at high ozone dosages and low temperature (5 °C). The findings of this research clearly show and imply that high-concentration ozone, carried by oxygen feed, is an efficient and sustainable alternative to chemical fungicides in the treatment of Fusarium wilt in hydroponic nutrient solutions because ozone decomposes quickly to oxygen, resulting in an environmentally safe and nontoxic residue.

KEYWORDS:

• Fusarium oxysporum
• hydroponics fungi
• ozone
• soil-borne plant pathogen
• sustainability

Acknowledgments

The authors of this research express sincere thanks to the U.S. Department of State for providing an International Fulbright S&T Award to the first author for carrying out this research at Iowa State University as part of the requirements for a PhD degree in Sustainable Agriculture. Also, we express appreciations and thanks to the U.S. Department of Energy Ames Laboratory at Iowa State University for providing the lab facility to conduct this research. We are very grateful to the reviewers for their constructive comments and suggestions that led to substantial improvements of this paper.

Additional information

Funding

This work was supported by the The Bureau of Educational and Cultural Affairs, US Department of State under the International Fulbright S&T Award to the first author, and this research was conducted at Iowa State University, Ames, IA, USA.