The two other types of experiment were quite similar except that one or the other of the two pathogens was inoculated with the barley roots and was therefore no longer healthy. “We then observed whether the production of the volatile compounds stemming from the diseased roots was similar or not. In the case where the bouquet was different, we determined if this new profile had an influence on the mycelial growth of the pathogen placed in the petri dish. We did this simply by comparing with the results of our first observations”, continues the researcher.

Finally, volatile compounds are different, in terms of their nature, their number and their quantity. “In the end, 23 molecules were specifically produced in the roots infected by Fusarium, and 21 by Cochliobolus. This was both remarkable and interesting”.  What was equally interesting was the fact that the exposure of the fungi to the diseased roots inhibited their growth by up to15%. This signifies that there are molecules that inhibit the growth of the pathogen in the bouquet of volatile compounds emitted by the diseased roots. But the question was; which molecules? “The problem at this stage of the research was to establish where these new compounds came from as they were produced by placing the roots and the pathogen in contact with each other. Among the different molecules, it was neccessary to be able to determine which came from the plant and which came from the pathogen”, concludes Professor Jijakli.

At this point in the research, which is the subject of a published article, the team of researchers had an idea of the overall effect of the bouquet. But they were unable to affirm that a maximum inhibition of 15% in the growth of the fungus was the result of an effective defense against the pathogen. Professor Jijakli and his team therefore wanted to go further, by testing the effect of the molecules one by one on the growth and germination of the fungis.

Two surprising candidates

By isolating the different compounds, the researchers came across two interesting molecules. These two molecules no longer inhibited the growth of the pathogen by 15% but by more than 70%. “Given such a result, we could imagine a gradual transition from basic research to the perfection of an effective defense against both diseases”, explains the delighted phytopathologist.