New Paenibacillus polymyxa strains isolated from different soils antagonistic to Aspergillus flavus and Fusarium oxysporum protects wheat sprouts from fungal infection

In this study, novel Paenibacillus polymyxa strains were isolated from different soils in the Rostov region of Russia and screened for their potential as biocontrol agents against agricultural fungal pathogens. Identification of the strains was confirmed via 16S rRNA gene sequencing, and antagonistic activity assays demonstrated significant inhibitory effects against phytopathogenic Aspergillus flavus and Fusarium oxysporum , indicating promising antifungal properties. To optimize antifungal metabolite production, a range of cultivation media and conditions were tested. Media with high protein content, such as LB and soy-based formulations, supported the highest levels of antifungal activity, whereas protein-deficient media showed markedly reduced effectiveness. Different application methods, including liquid suspensions and solid-phase fermentation, were also tested to determine the most effective method for crop protection. Vegetation experiments demonstrated that soil treatment with a solid-phase preparation containing P . polymyxa spores at a concentration of 10 ⁷ CFU/g significantly reduced Fusarium infection in wheat sprouts without impacting plant growth. Vegetation experiments confirmed the antifungal effects of these Paenibacillus preparations, effectively reducing Fusarium. These findings highlight the potential of these newly characterized P . polymyxa strains as effective biological fungicides for sustainable agriculture.