Biological soil disinfestation prevented the development of Fusarium vanleeuwenii root rot on lisianthus plants on ethanol-irrigated soil in Okinawa, Japan

Introduction- Biological soil disinfestation (BSD) is becoming popular outside Okinawa, Japan and is often conducted by using low concentrations of ethanol to irrigate the soil. Okinawa has a subtropical climate, and its soil is unique and different from that of other regions of Japan. The effect of BSD on farms in Okinawa remains unclear due to a lack of research conducted in the area. Materials and methods- This study investigated the effect of BSD using low concentrations of ethanol on Jahgaru soil in Okinawa on the change in the oxidation/reduction potential (ORP), pH, and bud cells of the pathogen isolated from Fusarium root rot. Results and discussion- The pathogen of Fusarium root rot was identified as Fusarium vanleeuwenii based on multigene sequence analyses. The oxidation/reduction potential (ORP) values decreased in Jahgaru soil irrigated with 0.5% and 1.0% ethanol solutions, reaching below zero in 5 days. The pH values of the Jahgaru soil irrigated with 0.5% and 1.0% ethanol solutions for 14 days were significantly lower than in the soil irrigated with groundwater. Additionally, F vanleeuwenii bud cells in Jahgaru soil irrigated with 0.5% and 1.0% ethanol solutions perished within 7 days. Fungicidal activity had already started when the ORP values were not below zero and the pH value had not decreased within the 4 days after BSD started. Thus, fungicidal substances are possibly generated even in an aerobic environment. In the field, the occurrence of Fusarium root rot decreased after BSD treatment in soil irrigated with 0.5% ethanol solution compared with the previous year. Additionally, the Fusarium number 0-30 cm deep in the field significantly decreased after BSD treatment. Conclusion- Therefore, BSD treatment on Jahgaru soil irrigated with 0.5% ethanol solution is effective for preventing Fusarium root rot of lisianthus caused by F vanleeuwenii in the field.