Impact of bacterial biological control agents on fumonisin B1 content and Fusarium verticillioides infection of field-grown maize

The effects of four bacterial biocontrol agents on Fusarium verticillioides infection and fumonisin accumulation in the maize agroecosystem were evaluated in a 2-year field study. The antagonistic abilities of the four agents were examined following two application techniques consisting of inoculating seeds during pre-sowing and maize ears at flowering. Seed inoculation with F. verticillioides and co-inoculation with this fungus and each of the four agents were also examined. Treatment effects on maize performance were also assessed through determination of the number of plants per hectare, kernels yield (kg ha−1) and kernel–cob relations. F. verticillioides infection and fumonisin B1 contents were determined in kernels of physiologically mature maize plants at harvest time. Maize yield remained unchanged with respect to controls in both field surveys; however significantly higher FB1 contents were obtained after inoculation of seeds with F. verticillioides M7075. Seed treatment with Bacillus amyloliquefaciens and Enterobacter hormaechei reduced the infection by the fungus and FB1 contents both years of the study while ear inoculation produced highly variable results. The number of colony forming units of F. verticillioides obtained from harvested maize kernels was positively correlated with fumonisin B1 content; however none of these parameters showed significant correlation with kernel yield. The overall results suggest that in years conducive for F. verticillioides infection and fumonisin production, seed treatment with Bacillus amyloliquefaciens and Enterobacter hormaechei may improve quality of maize grains obtained at harvest by reducing toxin content.