Bacillus cereus sensu lato strain B25 controls maize stalk and ear rot in Sinaloa, Mexico

Abstract

Fungal pathogens causing maize stalk and ear rot are a potential threat to grain production in regions where monoculture extensions can reach over 500,000ha per year. This particular problem is observed in northern Sinaloa, Mexico with the fungal pathogen Fusarium verticillioides. Three native Bacillus spp. strains isolated from the maize rhizosphere were tested for their potential as biocontrol agents (BCAs) against fusariosis in maize, during the 2011–2012 fall-winter growing season. Based on its performance, the Bacillus cereus sensu lato strain B25 was selected for further analysis. The effectiveness of maize seed inoculation with this strain was examined in two more consecutive growing seasons. The potential for B25 to control Fusarium stalk rot (FSR) and Fusarium ear rot (FER) of maize, as well as the accumulation of fumonisins in kernels, was thus assessed with white maize hybrids grown under different field conditions in northern Sinaloa, Mexico. FSR and FER incidence and severity were substantially reduced as compared to controls in all trials conducted. Fumonisin contamination in maize grains was also reduced (up to 93.9%) by B25 application, as compared to the control. Furthermore, B25 significantly increased grain yield in several trial sites or crop seasons, above the average of the untreated controls and consistently above the average of F. verticillioides-inoculated controls. Based on these findings, we propose that seed bacterization with strain B25, combined with adequate crop management practices, may become a useful tool for avoiding Fusarium stalk and ear rot of maize. This practice will also provide safe fumonisin grain levels for maize production in northern Sinaloa.