BIOLOGICAL-CONTROL OF FUSARIUM DISEASES BY FLUORESCENT PSEUDOMONAS AND NONPATHOGENIC FUSARIUM

In soil-less culture of vegetables and flowers in greenhouses, fusarium diseases may induce severe damage. Under these growing conditions, biological control could be achieved by application of selected strains of fluorescent Pseudomonas or non-pathogenic Fusarium oxysporum. Seventy-four strains of fluorescent Pseudomonas were tested for their ability to reduce the incidence of fusarium wilt of flax when applied either alone or in association with one preselected non-pathogenic strain of Fusarium oxysporum (Fo47). Four classes were established, based on the effect of bacteria on disease severity, on their own or in association with Fo47. Most of the strains did not modify the percentage of wilted plants. However 10.8% of them, although having no effect on their own, significantly improved the control attributable to Fo47. One of these bacterial strains (C7) was selected for further experiments. Two trials conducted under commercial-type conditions demonstrated the effectiveness of the association of the bacterial strain C7 with the non-pathogenic Fusarium strain Fo47 to control fusarium crown and root rot of tomato, even when each antagonistic micro-organism was not efficient by itself. The yields were not significantly different in the protected plots in comparison with the healthy control.