The choice of barley and these two fungi as a subject of study was not by chance. Barley is a cereal that is well-known in laboratories where it has already been the subject of many studies. For this reason there is a wealth of knowledge about this plant that can be tapped into. More concretely, the cultivation of this cereal easily exceeds one hundred million tonnes per year. Sensitive to a lot of pathogens, the shortfall in barley crops due to disease is in the region of 250 million dollars per year which is certainly not a negligible sum for the agricultural sector. Fusariosis and spot blotch disease are two of the main diseases affecting the plant. “The interest of understanding the interaction and communication between the plant and the pathogen was to try to find a way to perfect an efficient method for controlling these two diseases by taking inspiration from what is naturally produced by this interaction. At a time when the chemical products used to protect crops are being withdrawn from the market one by one, it is more important than ever to explore the biological route”. Professor Jijakli considers this route to be the correct one. “This is why we have gone as far as possible in the study of the volatile compounds emitted by the roots underground and their influence on the pathogens. Very little research has already been done with regard to the roots and, in particular, their response to the development of the fungi”.

How can the defense mechanism of barley be measured and isolated?

Part of the interaction between plants and pathogens takes place by means of the emission of volatile compounds. In the present study, the researchers were interested in the part of the response involving the roots. In a natural environment, it is difficult to observe this interaction and to determine which action causes which reaction. “The soil contains other bacteria, minerals, and other fungi, it was neccessary to simplify the system”, Continues the researcher. The entire study therefore took place in the laboratory. At first, only the volatile compounds of the fungi were studied in a sterile environment.  The development of these fungi made it possible to establish the fact that there was a real peak in the diffusion of these compounds on day seven. 

Then three other types of experiment were carried out, all of them in sterile hermitically sealed containers in order to avoid any outside influence. Firstly, healthy barley roots were placed in a nutrient solution allowing the plant to develop. A pathogenic fungus was placed in a Petri dish and was therefore not in direct contact with the roots but was indeed present in the same vessel. The researchers were able to analyse the distribution of chemical compounds emitted by the barley root, and at the same time, to measure the mycelial growth and the diameter of the pathogenic fungus.  The latter was measured daily for a period of 192 hours.