Characterization and selection of Bacillus sp strains, effective biocontrol agents against Fusarium oxysporum f. sp radicis-lycopersici, the causal agent of Fusarium crown and root rot in tomato

The antagonistic activities of 20 Bacillus isolates were tested with dual culture and greenhouse conditions against Fusarium oxysporum f. sp. radicis-lycopersici (FORL) race 0, the causal agent of Fusarium crown and root rot of tomato. Under dual culture, 10 isolates inhibited mycelial growth > 38% and the most effective inhibited fungal growth > 50%. The 20 Bacillus isolates were tested for production of volatiles, cyanide, antibiotics, and phosphorus solubilisation; 15 isolates produced volatiles that inhibited growth of pathogens, 9 isolates produced cyanide, 10 produced antibiotics, and five solubilised phosphorus. Greenhouse experiments with the same 20 isolates revealed the effectiveness of 12 strains, which increased the percentage of healthy plants in the tested cultivar from 66 to 96%. The best disease control was achieved by isolates B11, B5, B17, and B18. However, B11 and B17 were the only isolates that produced cyanide, antibiotics, solubilised phosphate and showed 44% inhibition of fungal growth. The selected strains could be considered in plant growth promotion and biological disease control.