Sensorial, biochemical and molecular changes in Raboso Piave grape berries applying "Double Maturation Raisonnée" and late harvest techniques.

At ripening, Vitis vinifera cv Raboso Piave grapes have high acidity, which results in an astringent wine that is not easy to drink. To overcome this limitation, several researches have attempted to alter the polyphenols profile mainly by applying different harvest techniques. The aim of this work was to investigate sensorial, biochemical, and molecular changes in Raboso Piave grape berries subjected to delayed harvests as Late Harvest (LH) and "Double Maturation Raisonnée" (DMR) techniques. At the molecular level, a microarray study was conducted comparing Traditional Harvest berries (TH) to LH and DMR ones. Gene ontology enrichment analysis pointed out that LH and DMR techniques affected metabolism of acids, sugars and polyphenols. A Principal Component Analysis, performed on transcriptomic data, pointed out that malate catabolism as well as some branches of flavonoids biosynthesis are significantly affected by DMR. In DMR grape berries, the flavonol and catechin accumulations were induced and depressed, respectively. In parallel, the transcription of flavonol synthase and leucoanthocyanidin-reductase 2, the main genes responsible for flavonol and catechin biosynthesis, were similarly induced and down-regulated. These changes resulted in a brighter colored wine with lower astringency.