Molecular and metabolite changes in response to postharvest dehydration in different wine grape varieties

Grape postharvest dehydration is a technique used to enhance specific berry quality traits for the production of special wines. Most of the modification affecting berries during this period are related to water loss and consequent berry juice concentration. In addition to this, many peculiar traits of dehydrated grapes are achieved through physical and biochemical changes occurring in berries which are, at least in part, under strict genetic control. In Verona (Italy) province, postharvest dehydration is traditionally employed for producing premium wines like Amarone, obtained mainly from Corvina grape, characterized by the capability to withstand a long period of post-harvest dehydration. To determine the suitability of different grape varieties to the postharvest dehydration, we analyzed and compared transcriptomic and metabolomic changes during the process in six varieties, Corvina, Sangiovese, Oseleta, Merlot, Cabernet Sauvignon and Shiraz, placed in the same environmental conditions. A general dramatic rearrangement of the berry transcriptome was observed during the postharvest period in all grapes, but Corvina was characterized by a much higher induction of gene expression compared to the other cultivars. On the contrary, this general activation appeared very weak in Cabernet Sauvignon. The six grape varieties showed also characteristic metabolite changes during the process. Overall these analyses suggest that postharvest dehydration represent a process that profoundly modifies and improves grape quality traits for cultivars characterized by a high level of induction of gene expression and a low dehydration rate