This gave rise to the idea of collaborative work between a set of Belgian and French institutions as part of an Interreg project to test not only the potential of living organisms (such as bacterial strains), but also to test the potential of certain molecules produced by the latter. As molecules are not living, they are, in fact, likely to develop their activities in a much wider set of conditions than bacteria and independently of the variability encountered in agricultural situations.

Multiple efficacy

The researchers were more particularly interested in the lipopeptides. These are antibiotic molecules composed of a cyclic sequence of 7 to 10 amino acids and a relatively long fatty acid chain (12 to 18 carbons). Due to their amphiphilic properties, these molecules are classified as biosurfactants: their physico-chemical and surface-active properties make them particularly appropriate for the treatment of plants. Among the lipopeptides, three families have been the subject of particular attention:  Iturins and Fengycins (molecules that are known to have anti-fungal properties), but also Surfactins (which are capable of strengthening the immunity of the plant and, to a lesser extent, helping it to fight against pathogenic bacterial agents).

The first part of the study consisted of gaining a better understanding of the mode of action of the three lipopeptides in question and then selecting new molecules similar to them in terms of their biochemical structure (cyclic peptides with fatty acid) and which were themselves likely to become the principal ingredients of biopesticides. “At Gembloux, we have been working on Bacillus and the lipopeptides for more than ten years. We have already accumulated some knowledge on their anti-fungal and immunostimulant activities. It was therefore natural that, together with the University of Lille, we used this solid scientific basis to initiate the project known as “Phytobio”, financed by the IV Interreg program”, explains Marc Ongena.

From the laboratory to the field

There was a seamless transition from the laboratory to the fields thanks to three main factors. Firstly, following three years’ work, the two university teams which were later joined by three other universities, (Ghent, Reims and Littoral Opal Coast) along with two technical centers (PCG and Inagro, in Flanders), were able to test the lipopeptides directly on leeks and lettuce, two crops that are economically important to the local economy, in the fields or in greenhouses.  “We gained a better understanding of the biochemical mechanisms underlying the antagonistic and immunostimulant properties of these lipopeptides. This enabled us to better define the optimal dosage of the product with regard to the expected effect” (1). Secondly, it was possible to isolate new natural molecules from bacteria of the Pseudomonas genus. “Even though we were not quite able to reach the stage of experimenting in the fields with these new molecules, their immunizing and/or antagonist potential is very promising”, explains the researcher from Liege. Last but not least, the trans regional collaboration made it possible to set up an experimental bioreactor that works in continuous and not intermittently as is usually the case and which is likely to be an equally promising mode of production in industrial terms.

(1) The action mechanisms of these lipopeptides on several diseases affecting grapevine, rice and barley plants have also been studied, but only in the laboratory.