Selection of rhizobacteria for biocontrol of Fusarium verticillioides on non-rhizospheric soil and maize seedlings roots

Fusarium verticillioides is a soil-borne plant pathogen of maize plants ( Zea mays L.) responsible for major yield losses by causing root, stalk, and ear rot and quality losses due to mycotoxin accumulation on grains. Recently, biological control practices have proven to be effective in controlling plant pathogens and the selection of distinct biocontrol agents with new competitive abilities is essential since they characterize new pathogen control approaches. This study aimed to isolate maize rhizobacteria as potential biocontrol agents against F. verticillioides and to evaluate their effect on maize seedlings’ growth. Among several candidates, the isolates Bacillus safensis RF69, Bacillus sp. RP103 and Bacillus sp. RP242 were selected due to an intense in vitro antifungal ability. All individual rhizobacterial treatments and a Combined Bacterial Mixture (CBM) were effective in reducing fungal counts on non-rhizospheric soil and on maize seedling rhizosphere, as well as in improving seedling growth parameters in comparison to the control plants. Treatments with the isolate Bacillus sp. RP103 and the CBM showed the most promising results regarding fungal antagonism. Our results indicate that the prophylactic treatment of field soil and maize seeds with the individual or a consortium of the rhizobacterial isolates can be an effective strategy to reduce F. verticillioides ’ density on soil and the rhizospheric contamination of maize seedlings. In addition, this is the first study that describes in vitro and in planta biocontrol of Fusarium verticillioides by B. safensis individually and in combination with other Bacillus spp., highlighting its potential biocontrol applications.