Impact of postponed harvests and withering on the aromas development of Moscato Giallo “Fiori d’Arancio” berries

Abstract

Composition of grape berries, and consequently wine characteristics, can be deeply modified by late harvest (LH) or withering techniques. Alternatively, a practice called “Double Maturation Raisoned” (DMR) has been developed, consisting in the cut of fruit-bearing vine following by the “reasoned” harvest. DMR differs from late ripening or withering (W) techniques, mainly for what concerns water loss rates and re-programming of berry metabolism especially in clusters located below the cane cutting. These events lead to significant changes in composition of berry, in particular in terms of secondary metabolites. The aim of this study was to investigate sensorial, biochemical, molecular and metabolic changes in Vitis vinifera cv Moscato Giallo (Yellow Muscat) grape berries subjected to LH, W and DMR techniques. Molecular analyses, carried out by quantitative Real Time-PCR, pointed out significant differences in the expression of genes involved in both primary and secondary metabolisms. As concerns primary metabolism, according to biochemical analysis, in LH-, DMR- and W-berries was observed an up-regulation of genes involved in sugars biosynthesis and down-regulation of those involved in malate catabolism when compared to TH. As regards secondary metabolism, transcripts involved in terpene biosynthesis (such as DXS and DHR), were significantly induced in DMR- and W- berries. Analysis of volatiles, carried out by means GC/MS, indicated that DMR and withering wines were characterized by higher levels of monoterpenes, such as linalool, linalool oxides, homovanillic alcohol/acid and α- terpineol, compared to TH and LH. Our results suggest that in Moscato giallo berries DMR causes an accumulation of terpenes, due to the transcriptional regulation of the related genes in response to the water loss, exalting the typical aromatic bouquet of this variety.