Stilbenes: biomarkers of grapevine resistance to fungal diseases

Since the introduction of powdery and downy mildews in Europe in the late 19th century, breeding resistant cultivars by hybridizing V. vinifera (susceptible) with other Vitis species (resistant) has been largely used and led, in 1947, to the cultivation of > 350,000 ha (23%) of grapevine area in France. Because of the poor wine quality of this first generation of hybrids, legislation prohibited their cultivation for the production of quality wines. Recent investigations allowed sequencing the entire grapevine genome, but no precise resistance genes are yet known for further introduction in susceptible V. vinifera cultivars. At the molecular level, the use of QTL (Quantitative Trait Loci) as resistance markers is ongoing and could be correlated to resistant gene expression and further define metabolite production in resistance mechanisms. Stilbenic phytoalexins are key defence molecules implicated in the resistance of grapevine cultivars to three major fungal pathogens, Botrytis cinerea (grey mould), Plasmopara viticola (downy mildew) and Erysiphe necator (powdery mildew). HPLC analysis of stilbenes is an efficient method to evaluate the ability of the vine plants to inhibit the development of fungal pathogens. Resistant grapevine varieties react very rapidly to infections by producing high concentrations of the most toxic stilbenes, delta-viniferin and pterostilbene, at the sites of infection. Monitoring of such stress biomarkers is also of great interest for evaluating the efficiency of priming molecules at inducing the grapevines' natural defence responses. In addition, these compounds have various beneficial effects on human health, acting as anti-oxidants and also as potential chemopreventive agents. The diversity of stilbenes is intriguing, and new holistic analytical approaches, such as metabolomics, that are widely used for wine classification also have great potential for the comprehensive study of responses of Vitaceae to biotic and abiotic stress.