Philippe Jeandet

Biological Activity of Resveratrol, a Stilbenic Compound from Grapevines, Against Botrytis cinerea, the Causal Agent for Gray Mold

The biological activity of resveratrol, a stilbenic compound synthesized by grapevines in response to various stresses, was reevaluated against Botrytis cinerea using a novel in vitro system that enabled direct observation of the fungus with an inverted microscope. We determined that 90 μg resveratrol/ml reduced germination of B. cinerea conidia by ca. 50%. Moreover, resveratrol was shown to significantly reduce mycelial growth of B. cinerea at concentrations ranging from 60 to 140 μg/ml. Exposure to resveratrol at concentrations ranging from 60 to 140 μg/ml resulted in cytological changes in B. cinerea, such as production of secondary or tertiary germ tubes by conidia, cytoplasmic granulations, protoplasmic retractation in the hyphal tip cells, and formation of curved germ tubes. These data reinforce the role played by this compound in the B. cinerea–grapevine interaction.

Analysis of resveratrol in Burgundy wines

Recent studies have shown that resveratrol (3,5,4‐trihydroxystilbene), a phytoalexin related to grape disease resistance, could occur in American and Bordeaux wines. It was also suggested that resveratrol might have cardioprotective activities in humans, as a result of drinking wine. We report here the presence of this compound in Burgundy wines. Analysis of resveratrol in wine was carried out using gas chromatography and gas chromatography—mass spectrometry.

The production of resveratrol (3,5,4'‐trihydroxystilbene) by grapevine in vitro cultures, and its application to screening for grey mould resistance

The ability of grapevine in vitro cultures to synthesise the phytoalexin precursor resveratrol in response to ultraviolet light irradiations is investigated in order to develop methods for screening for resistance to grey mould (Botrytis cinerea Pers.) in grapevines produced as a result of somatic embryogenesis. It is demonstrated that resveratrol formation can be reproducibly induced in leaves of in vitro plantlets. Differences in the production of resveratrol among the three varieties of Vitis vinifera tested (Pinot Noir, Chardonnay and Cabernet Sauvignon) were consistent with observations regarding their field susceptibility to grey mould. The use of phytoalexin induction and of in vitro methods as a tool for selection of Vitis resistant genotypes in early screening tests is discussed.

The Significance of Stilbene-Type Phytoalexin Degradation by Culture Filtrates of Botrytis Cinerea in the Vine-Botrytis Interaction

Phytoalexins, antimicrobial compounds, synthesized by a plant in response to infection or a variety of stresses are known to be the most efficient way by which grapevines withstand an attack by Botrytis cinerea Pers., the causal organism for grey mould. In that plant, such responses include the production of a simple stilbene, resveratrol, and the biosynthetically related compounds, viniferins and pterostilbene. If stilbene-type phytoalexins represent a contributory factor in the resistance of grapevines to B.cinerea, the capacity of the pathogen to metabolize antifungal compounds released by the host could also play a significant role in the outcome of the interaction between grapevines and B.cinerea.Indeed, the net accumulation of phytoalexins within plant tissues infected by various pathogens is probably controlled by a balance which may result, on the one hand, from the ability of the host cells to resist colonization by creating an inhibitory barrier for the parasite, and, on the other hand, from tolerance of the pathogen to antifungal compounds produced by the plant and from its ability to detoxify the phytoalexins to which it is exposed. Thus, the resistance of plants to infection depends on the phytoalexin production/degradation balance following attack by the pathogen. A variety of factors can alter this balance in favour of either the parasite or the host, resulting in non-compatible or compatible interactions. Among these, the capacity of B.cinerea to detoxify the phytoalexins produced by grapevines was investigated. We present here good evidence that this fungus produces a stilbene oxidase which can degrade resveratrol and pterostilbene. No detoxication of stilbenes is detected during the germination process in vitro, suggesting that stilbene-degrading activity does not seem to be constitutive in dormant conidia of Botrytis.