Multifunctional action of Bacillus subtilis for Fusarium verticillioides biocontrol and growth promotion in corn seeds

This study aimed to evaluate the in vitro antifungal activity and corn seed protective effect of two Bacillus subtilis isolates in two formulations, against Fusarium verticillioides, along with their indole acetic acid, siderophore production, and phosphate solubilization ability. Antifungal activity of two Bacillus subtilis isolates (NT1 and NT2) was investigated against F. verticillioides 97L in solid media and on corn seeds. Both B. subtilis isolates showed antifungal activity through production of diffusible antifungal compounds and NT2 showed the highest radial growth inhibition (61.7%). The seed treatments with B. subtilis based formulations, powder (P) and suspension (S), reduced the disease severity index compared to the control (P < 0.05), therefore they were efficient in inhibiting F. verticillioides 97L growth in corn seed and had no negative effects on seed germination and vigor. Concerning the vigor test, treatments with B. subtilis NT1(P) and NT2 (P) demonstrated a significant (P < 0.05) increase in shoot length and biomass production in comparison to the untreated seeds, which can be related to the ability of these isolates to produce indole acetic acid and to solubilize phosphate. None of the isolates produced siderophores. The B. subtilis isolates (NT1 and NT2) are promising biocontrol agents for developing new multifunctional formulations intended for management of corn disease caused by F. verticillioides as an alternative to chemical fungicides. Despite the efficacy observed in the current study, further research is required to evaluate the shelf-life and stability of the powder and suspension formulations under various storage conditions.