Biocontrol Potential of Rhizobacteria Against <i>Passalora fulva</i> and <i>Tuta absoluta</i>: A Sustainable Approach for Tomato Protection

Plant growth-promoting rhizobacteria (PGPR) offer a sustainable strategy for enhancing crop productivity and suppressing phytopathogens. In this study, seven bacterial isolates obtained from the rhizosphere of healthy tomato plants were evaluated for their antagonistic activity against the fungal pathogen <i>Passalora fulva</i>, the leaf miner <i>Tuta absoluta</i>, and their effects on tomato growth. In vitro dual-culture assays revealed that isolates IQR1, IQR2, IQR3, and IQR5 significantly inhibited <i>P. fulva</i> mycelial growth, with inhibition rates exceeding 35%. Volatile organic compounds (VOCs) produced by the bacterial isolates exhibited considerable antifungal activity, with IQR5, IQR1, and IQR2 achieving over 84% inhibition. Molecular identification based on 16S rDNA sequencing indicated that these isolates belong to distinct taxa: <i>Leucobacter aridicolis</i> (ON799334.1) (genus <i>Leucobacter</i>), <i>Paenochrobactrum</i> sp. (JF804769.1) (genus <i>Paenochrobactrum</i>), an uncultured bacterium (JQ337400.1) (genus <i>Psychrobacter</i>), and marine bacterium AK6_052 (KF816539.1) (genus <i>Brevundimonas</i>). Under greenhouse conditions, isolates IQR3, IQR5, and IQR1 reduced disease incidence of <i>P. fulva</i> to 20–26%. The same isolates also promoted plant growth, enhancing stem height and collar diameter. In addition, IQR5 significantly reduced <i>T. absoluta</i> larval density and foliar damage, with the number of larvae per leaflet decreasing to 1.42, compared to 3.20 in the control. These findings highlight the potentials of these rhizobacterial strains—particularly IQR5—as effective biocontrol agents and biofertilizers for integrated pest and disease management in tomato cultivation.