Suppression of Fusarium verticillioides in maize by Bacillus subtilis and Micrococcus luteus: evidence from...

A total of 204 rhizobacterial isolates from 39 maize rhizospheric soil samples were screened for antagonism against Fusarium verticillioides. Fifty-six isolates (27%) inhibited fungal growth in dual culture assays, with 27 cultures showing strong inhibition (>35%). The bacterial isolates were further evaluated for biocontrol related attributes, including ammonia, hydrogen cyanide, chitinase, β-1,4-glucanase, protease, amylase, and lipase production, along with plant growth-promoting traits such as phosphate, zinc, and iron solubilization and the production of indole-3-acetic acid (IAA) and gibberellic acid (GA₃). Based on their multifunctional traits, seven promising isolates (MRB5, MRR1, FR8, MRD9, MRJ1, MRK4, and MRJ4) were examined for maize growth (PMH 14) seedling blight suppression under fungal infested mini pot-controlled conditions. Seed biopriming with Bacillus subtilis (MRB5) and Micrococcus luteus (FR8) significantly improved germination and seedling growth, underscoring their role as potent antagonists. Glasshouse evaluation of MRB5 and FR8 isolates as individual and in combination, confirmed the effectiveness of dual inoculation yielding highest seed germination (91.11%) and plant height (119.41 ± 0.43 cm) and lowest seedling blight incidence (9.89%). Co-inoculation of bacterial antagonists also disclosed their effectiveness in alleviating the defense response of maize plants by increasing the phenolics, peroxidase, and phenylalanine ammonia lyase activity, as a mechanism of suppressing F. verticillioides induced pathogenic effects.