"BIOMOLCHEM": A TOOL TO ASSESS THE DEFENSE STATUS OF GRAPEVINES AFTER STIMULATIONS OR NOT OF CULTIVAR OR RESISTANT GENOTYPES, FROM GENES TO THE FIELD

Stimulating plant defenses or resistant plant varieties is promising as an alternative method for limiting pesticide use in agriculture. To assess the defense status of the grapevine we have developed a triple approach called “BioMolChem”.
The biological tests measure the efficacy of grapevine defenses against two major biotrophic pathogens (Erysiphe necator, Plasmopara viticola). Molecular assays by q-RT-qPCR show the expression patterns (over-expression or repression) of 20 genes involved in grapevine defenses, and they can then be correlated or not with the level of protection. Biochemical analyses of phenylpropanoides by HPLC are used to quantify and identify molecules of interest, and correlate them with specific gene expression (stilbene biosynthesis) and the acquired protection. This tool was tested on leaves (‘Cabernet Sauvignon’) after stimulation by different elicitors (benzothiadiazole, phosphonates), on grapevine, ‘Cabernet Sauvignon’, genotypes resistant to powdery and downy mildew, and in the vineyard. We obtained correlations between the expression of PR-protein genes and genes coding for biosynthesis pathways (stilbene, tryptophan) and with the level of protection. Similarly, we found correlations between the presence of known and unknown molecules and the level of protection. Resveratrol, a well-known phytoalexin of the grapevine, is a good marker of defense status but not of protection. Therefore, we now have available a tool for understanding the defense and protection status of the grapevine in laboratory and field experiments.