Fusarium root rot

bacterial biocontrol

olive

Plant pathology

Fungi

Biocontrol research has the potential for managing Fusarium root rot of olive. This latter is treated by the use of isolated bacteria from the soil of olive orchards of Tunisia: Bacillus Licheniformis and Enterobacter Colcae. It was demonstrated that these two bacteria are effective against Fusarium solani and oxysporum. In an initial screening, two efficacy bacteria were isolated with a reduction of disease incidence. In vitro, both biocontrol agents were highly tolerant to the carbendazime fungicide commonly used to control Fusarium diseases. It was observed that carbendazime reduced disease symptoms at a concentration of >50 μg mL⁻¹. The combination of the bacterial isolates and carbendazime gave a significant (P≤0, 05) control of the disease when plants were artificially inoculated with the pathogen. The application of carbendazime at a low concentration (10 μg mL⁻¹) in combination with Bacillus B4 reduced disease symptoms by 51%, compared with a reduction of 46% obtained with the bacterium alone and no control with the chemical treatment alone. A combination of Bacillus with fungicide increased the application rate of 10 μg mL⁻¹ carbendazime and significantly reduced disease symptoms by 74% compared to 34% with carbendazime treatment alone and, respectively, a combination fungicide and Enterobacter E4 increased the disease by 84% compared with 55% for bacteria alone. In this experiment, the integrated treatment also slightly outperformed the application of 100 μg mL⁻¹ bacteria Bacillus and Enterobcater applied, and without fungicide also provided good disease control.