Production of a Mixed Inoculum of Fusarium oxysporum Fo47 and Pseudomonas fluorescens C7 to Control Fusarium Diseases

Abstract

Strains of non-pathogenic Fusarium oxysporum and Pseudomonas fluorescens are effective biocontrol agents against Fusarium diseases. Use of strain Fo47 of F. oxysporum in combination with strain C7 of P. fluorescens improves disease control in comparison to application of Fo47 alone. To develop a product based on a combination of these two strains, it would be beneficial to produce and formulate both organisms together. When an irradiated peat was inoculated with these strains either alone or in combination, they grew actively and reached similar maximum population densities irrespective of the initial inoculum concentration (1×10³ and 1×10⁶ g⁻¹ of peat) and mode of inoculation. These populations survived well with only a slight decrease in population densities after 11 months storage at 25°C. A bioassay was performed to evaluate peat and microbial suspension inocula of C7 and Fo47 alone or in combination against the flax pathogen, F. oxysporum f. sp. lini. Biocontrol activity of the peat-produced inocula was as effective as the suspensions. There was no dose–response relationship for C7, and when C7 was used as a mixed inoculum with Fo47, the biocontrol activity was always greater than that provided by Fo47 alone. This process could be used to produce an effective mixed inoculum with a shelf life of one year or more.

Keywords:

• Fusarium oxysporum
• Pseudomonas fluorescens
• biocontrol agents
• production
• formulation
• dose response relationship

Acknowledgments

The authors acknowledge Patrick Wadoux (Lyphatec) for providing the bags of irradiated peat, Daniel Pouhair, Christiane Dreumont, and Krystyna Stawiecky for technical assistance, Martine Janisz for bibliography and secretary assistance.