Abstract
One of the most destructive tomato diseases is Fusarium wilt, caused by Fusarium oxysporum f. spp. lycopersici (FOL), which leads to substantial losses in tomato production in Saudi Arabia. Under organic farming conditions, disease management based on chemical treatment is restricted. Therefore, environmentally friendly alternative control strategies are needed. In this study, we investigated the effectiveness of the use of a native rhizobacteria integrated with organic compost to manage FOL. Twenty rhizobacterial strains were isolated from the rhizosphere of commercial tomato fields. Molecular identification of the 16S rRNA gene showed that the strains belonged to five genera, namely: Bacillus, Pseudomonas, Stenotrophomonas, Enterobacter, and Achromobacter. Screening of antagonistic activity using dual cultures and culture-filtrate assays identified Bacillus subtilis strain KSU-110 as having the highest activity against FOL. Treating tomato plants with this antagonistic strain either alone or in combination with compost resulted in the reduction of the wilt disease under both greenhouse and field conditions. The combination of KSU-110 with organic compost significantly (P < 0.05) reduced the FOL population in the tomato rhizosphere and improved plant growth. Moreover, systemic resistance was enhanced in tomato plants through the induction of defense-related enzymes, including peroxidase and polyphenol oxidase. Taken together, the results of this study suggest that the combination of the native rhizosphere strain KSU-110 and organic compost has the potential to control tomato wilt under organic farming conditions in Saudi Arabia. (C) 2020 Friends Science Publishers