Effects of maize inoculation with Fusarium verticillioides and with two bacterial biocontrol agents on seedlings growth and antioxidative enzymatic activities

Abstract

Maize (Zea mays L.) is a staple food for the majority of the world's population and different diseases may affect its emergence, growth and development. Fusarium verticillioides (Sacc.) Nirenberg (Teleomorph: Gibberella moniliformis Wineland) is the most commonly reported fungal species infecting this crop. The present work analyzes the bioprotective role of two bacterial agents, Bacillus amyloliquefaciens and Microbacterium oleovorans, against F. verticillioides in maize. Maize growth parameters, count and identification of Fusarium isolates as well as CAT, SOD, APX and POD activities were evaluated in 10 and 20 days old seedlings in relation to single inoculations and co-inoculations of the fungus and the bacterial agents. Endophytic count of F. verticillioides propagules was reduced after inoculation with B. amyloliquefaciens during both evaluated periods (10 and 20 days) while M. oleovorans presented a variable performance as an F. verticillioides antagonist. Inoculation with F. verticillioides promoted an increase in SOD activity in roots of 10 days old maize seedlings. S/R ratios of these seedlings were also significantly affected by inoculation with the fungus. Results suggest an early response of maize to infection, since such variations in enzyme activities and plant growth parameters were not observed 20 days after treatment. Moreover, no differences were observed in the number of POD isoforms between infected and non-infected plants. The overall results point out that maize infection by F. verticillioides may be attenuated after seed inoculation with B. amyloliquefaciens and this infection may represent a weak stressful factor, eliciting minor changes in the antioxidative response at early stages of plant growth.