Mapping aromatic profiles of Chardonnay and Sangiovese wines in grafting combination with new rootstocks

Abstract

Rootstocks play a key role in the adaptation of grapevine to environmental conditions, affecting phenology, vigour, yield and grape quality. Thus, the choice of the grafting combination become crucial in maintaining qualitative standards of wine under changing climate. Several studies assessed the effect of rootstocks on grape and wine quality in terms of sugar/alcohol content, acidity and phenolic compounds, but the effect of rootstocks on aromatic volatile compounds is nowadays poorly investigated. The aim of this work is to characterize the aromatic profile of white and red wines under different grafting combinations.

The study was conducted in 2022 in vineyards of Chardonnay, located in Franciacorta, and Sangiovese, located in Montalcino. In both fields, 3 different grafting combinations were compared, including rootstock SO4 and two recently released rootstocks, M1 and M4. During harvest, about 50kg of grapes from each grafting combination were collected to obtain separate experimental wines, using the same oenological protocol. A chemical characterization of the resulting wines was carried out, detecting technological and phenolic parameters, a total of 150 aromatic volatile compounds and over 50 aroma precursors. Aromatic compounds and precursors were quantified using HS-SPME GC-MS, except for thiols and glycosylated precursors measured with online SPE HPLC-MS/MS. Finally, the sensory profile of experimental wines was evaluated through a technical tasting, performed by a panel of 10 tasters. Obtained data were analyzed using a multivariate approach.

The odor detection threshold exceeded for 31 and 29 aromatic volatile compounds in Chardonnay and Sangiovese wines, respectively. Two principal components were identified using PCA: the first one discriminating for varieties (58%), and the second one for rootstocks (16%). Main aroma compounds contributing to PC2 were Ethil Eptanoate and ß-Damascenone, higher for Sangiovese/M1, as well as Isobutyl Acetate, higher for Chardonnay/M4. Significant differences between rootstocks were found on sensory profiles of both varieties. Links between chemical and sensory profiles were highlighted by RDA. Generally, terpene precursors were higher in wines obtained in grafting combination with SO4, whereas thiol and norisoprenoid precursors with M4.