FATE OF 2 MICROORGANISMS IN MAIZE SIMULATED RHIZOSPHERE UNDER HYDROPONIC AND STERILE CONDITIONS

The interaction, between a rhizobacterium (Pseudomonas sp.) of maize and the agent of root rot of maize (Fusarium graminearum), was studied in vitro under hydroponic and sterile conditions. The Pseudomonas showed an antagonistic activity, in vitro, towards F. graminearum. The bacteria inhibited fungal growth, but the inhibition depended on the agar medium used. The antifungal activity of antagonistic bacteria was due to the production of antibiotics, volatile compounds and siderophores. The fate of the two microorganisms was investigated in a simulated maize rhizosphere. Under hydroponic and sterile conditions, both microorganisms grew well in the presence of root exudates used as nutrients. As a result of competition between both microorganisms for the C source, the presence of F. graminearum affected the survival of the bacterium and, conversely, the Pseudomonas sp. reduced germination of F. graminearum.