Different solid bioformulations of the endophytic bacterium Streptomyces mutabilis CA2 with antifungal potential induced differential suppression on tomato Fusarium wilt

This study highlights the efficacy of a biofungicide based on spores of the endophytic Streptomyces mutabilis CA2 isolated from a Saharan native plant for controlling tomato root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici strain LB24, isolated from infected tomato field in Algeria. Among twelve actinobacterial strains screened in vitro, CA2 exhibited the strongest antifungal activity and was therefore selected. The CA2 spores were formulated in three eco-friendly carriers: talcum powder, alginate pellets, and alginate–clay pellets. Pot experiments using autoclaved and non-autoclaved soils included seven treatments: positive and negative controls, a chemical fungicide (Tebuconazole®), a commercial biofungicide (Serenade®), and the three CA2 spores-based formulations. Compared to the positive control, all formulations significantly reduced DSI, with the CA2 spores-based talcum powder showing the strongest effect (P < 0.001), achieving 91.5% and 92.5% reduction in autoclaved (P < 0.0001, R² = 0.90) and non-autoclaved (P < 0.0001, R² = 0.85) soils, respectively. Alginate-based formulations also provided significant protection (P < 0.005), though slightly lower than the talcum-based one. In addition to disease suppression, CA2 spores-based formulations significantly improved seedling growth compared with both the biological and chemical fungicides. The CA2 spore talcum formulation offers both disease control and plant growth promotion, representing a sustainable, eco-friendly alternative to chemical fungicides for managing tomato root rot by Fusarium oxysporum f. sp. radicis-lycopersici strain LB 24.