Effect of high CO 2 pretreatment on quality, fungal decay and molecular regulation of stilbene phytoalexin biosynthesis in stored table grapes

Abstract

Table grapes ( Vitis vinifera) cv. Cardinal stored at low temperature were analysed to determine the effect of pretreatment with 20 kPa O 2 + 20 kPa CO 2 + 60 kPa N 2 for 3 days on quality and control of decay. The pattern of stilbene synthase (STS) gene expression and trans-resveratrol levels were also analyzed in grapes during low temperature storage at 0 °C and further shelf-life at 20 °C for 2 days. Our results showed that high CO 2 pretreatment was effective for improving appearance of the bunches and maintaining the quality of the berries. In CO 2-treated bunches the browning and withering index, the decline in relative water content and the weight loss were also lower than in non-treated ones. The levels of STS mRNA and the accumulation of trans-resveratrol in CO 2-treated grapes were much lower than in the non-treated grapes during low temperature storage. Moreover, the pattern of STS gene expression and trans-resveratrol content in CO 2-treated grapes was consistent with the reduction of natural total decay produced by this pretreatment. This effective non-stressing treatment avoids the induction of trans-resveratrol during low temperature storage until its synthesis is enhanced during shelf-life at 20 °C.