Vol. 9, Special Issue 9, Part O (2025)

Biological control using beneficial microorganisms, particularly Bacillus subtilis, offers an eco-friendly strategy for managing soil-borne plant pathogens. The present study evaluated five B. subtilis isolates (BS1-BS5) against major soil pathogens (Fusarium oxysporum f. sp. capsici, F. oxysporum f. sp. ciceri, Sclerotium rolfsii and Rhizoctonia bataticola) using the dual culture technique. Significant differences were observed among the isolates in their antagonistic potential. Against F. oxysporum f. sp. capsici, isolate T₄ exhibited the highest inhibition (76.60%), followed by T₃ and T₁. In the case of F. oxysporum f. sp. ciceri, isolates T₂ and T₄ showed maximum inhibition (82.13%). For S. rolfsii, isolates T₃ and T₄ recorded the strongest antagonism, with inhibition exceeding 80%. Similarly, against R. bataticola, isolates T₅ and T₄ demonstrated the highest suppression, with inhibition up to 88.25%. Overall, all B. subtilis isolates significantly reduced pathogen growth compared to the control, with T₂, T₃, T₄ and T₅ showing strong and consistent antagonistic effects. These findings corroborate earlier reports highlighting the efficacy of B. subtilis as a biocontrol agent through mechanisms such as production of antifungal metabolites, competition and rhizosphere colonization. The results confirm the promise of B. subtilis isolates, particularly T₄ and T₅ as effective candidates for the biological management of soil-borne diseases such as wilt, collar rot and dry root rot in crops.