Multifunctional rhizosphere bacteria for sustainable management of tomato foot rot caused by Rhizoctonia solani: Integrated in vitro and greenhouse evaluation

Tomato foot rot caused by Rhizoctonia solani Kühn is a destructive soil-borne disease causing severe seedling mortality and yield losses. This study evaluated multifunctional rhizobacteria for sustainable management of tomato foot rot through pathogen characterization, in vitro screening, and greenhouse validation. The pathogen isolated from infected stem tissue was identified as R. solani MRLJ1 (AG-3) based on morphological characteristics, ITS rDNA sequencing (GenBank accession PX487865), and AG-3-specific PCR. Twenty-eight rhizobacterial isolates were screened for plant growth-promoting and biocontrol traits, including indole-3-acetic acid (IAA; 0.08–13.92 µg mL −1 ), siderophore production (6.24–93.58%), ammonia production (6.68–18.68 µg mL −1 ), phosphate solubilization (2.13–5.26), nitrogen-fixation-associated growth, hydrogen cyanide production, and lytic enzyme activities. Dual-culture assays revealed substantial variation in antagonistic activity (13.79–56.25%), with P2.B and M5 showing the highest inhibition of R. solani (56.25% and 53.44%, respectively), accompanied by pronounced hyphal abnormalities. Molecular identification confirmed P2.B as Bacillus subtilis MRLJ4 and M5 as Bacillus albus MRLJ5. Greenhouse evaluation demonstrated marked improvements in tomato growth and disease suppression following bacterial treatment. P2.B reduced disease severity from 91.33% in the pathogen control to 26.67%, corresponding to approximately 70.8% disease reduction, while M5 reduced disease severity to 40.00% (56.2% reduction). A bacteria-only experiment further demonstrated the intrinsic growth-promoting capacity of both isolates in the absence of R. solani . Overall, P2.B and M5 emerged as promising multifunctional candidates for sustainable biological management of tomato foot rot.