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

The interaction, between a rhizobacterium (Pseudomonas sp.) of maize a nd the agent of root rot of maize (Fusarium graminearum), was studied in vitro under hydroponic and sterile conditions. The Pseudomonas show ed an antagonistic activity, in vitro, towards F. graminearum. The bac teria 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 m aize rhizosphere. Under hydroponic and sterile conditions, both microo rganisms grew well in the presence of root exudates used as nutrients. As a result of competition between both microorganisms for the C sour ce, the presence of F. graminearum affected the survival of the bacter ium and, conversely, the Pseudomonas sp. reduced germination of F. gra minearum.