Elicitors used as a tool to increase stilbenes in grapes and wines

Abstract

The economic importance of grapevine as a crop plant makes Vitis vinífera a good model system to study the improvement of the nutraceutical properties of food products (Vezulli et al. 2007). Stilbenes in general, and trans-resveratrol in particular, have been reported to be responsible for various beneficial effects. Resveratrol´s biological properties include antibacteria and antifungal effects, as well as cardioprotective, neuroprotective and anticâncer actions (Guerrero et al. 2010 ). Stilbenes can be induced by biotic and abiotic elicitors since they are phytoalexins (Bavaresco et al. 2001). Grapevine phytoalexins (plant metabolites with antimicrobial activity that are synthetized de novo and fuction as the basis of a disease resistance mechanism) are stilbene compounds synthetized and accumulated in leaves and berries in response to abiotic stresses. Numerous experimental trials have recently been conducted with diferent elicitors to promote stilbene synthesis in grapevine berries, such UV irradiation (Cantos et al. 2003; Langcake and Pryce, 1977), aluminium chloride (Adrian et al. 1996), ozone (González-Barrio et al. 2006), methyl jasmonate (Vezulli et al. 2007) and benzothiadiazole (Iriti et al. 2004) . Since a highest presence of stilbenes in grapes could be a protecion against mould infection, the application of these compounds could, not only improve the healthiness of grapes, but also limit the use of fungices. The stilbenes found in wine occur mainly in the skin of grape berries, and they pass from grape to wine during alcoholic fermentation, so, at the same time, the wines elaborated with these grapes would be considered healthier wines. In our study, five preharvest treatments considered as elilicitors, were applied in Monastrell grapes by means five elicitors: benzothiadiazole, methyljasmonate, shell chitosan, fungal chitosan and cell wall yeast. These compounds were applied as sprays on clusters at veraison and one week later. Our main objetive was to check wether these treatments could enhance stilbene accumulation in berries at the moment of harvest, and then to be extracted during winemaking. For this target, we identified, quantified and compared the stilbene content in grapes and wines elaborated with grapes from the diferent treatments against grapes and wines without no treatment consdered as a control. The results showed that only some of these compounds improved significantly the stilbene concentration in grapes but almost of them increasing their stilbene composition at the end of alcoholic fermentation, mainly trans-resveratrol which is considered as the highest biological value.