Stilbene compounds and stilbene synthase expression during ripening, wilting, and UV treatment in grape cv. Corvina.

The content of selected phenolic compounds including resveratrol (trans-3,5,4'-trihydroxystilbene) and its cis-isomer and glucosides (piceides) were monitored in grape (Vitis vinifera L. cv. Corvina) berry skin during ripening in the vineyard and in response to the post-harvest drying process (wilting). Four wilting conditions were compared (traditional, mixed, low-temperature, and high-temperature) to verify the eliciting effect of drying on resveratrol production. During fruit ripening the cis-piceid was the major stilbene found in berry skins, and a weak accumulation of stilbene synthase (STS) mRNA was observed, whereas UV-light irradiation greatly stimulated STS transcript of unripe berries. A time-course experiment showed the highest STS mRNA accumulation and resveratrol content (34 microg/g fresh weight at 58 days) occurring in berry skins in a mixed wilting process.