The Influences of Rootstock on the Performance of Pinot Noir (Vitis vinifera L.): Berry and Wine Composition

Background and Aims. Rootstocks are widely used in the viticulture industry to manage biotic stress, particularly the infestation of phylloxera, and to improve tolerance to abiotic stress. Grafting grapevines to rootstocks affects the berry quality and may influence the wine composition. This project investigated the impacts of 14 different rootstocks on the berry and wine chemical properties, phenolic profile, and volatile profile of grafted Vitis vinifera L. cv Pinot noir MV6. Methods and Results. This study was conducted at a commercial vineyard located in Mornington Peninsula, Victoria, Australia. The scions of V. vinifera L. cv Pinot noir clone MV6 were grafted onto 14 rootstocks, including 101-14 Millardet et de Grasset (101-14 Mgt), 1103 Paulsen, Selection Oppenheim (SO4), 110 Richter, Schwarzmann, 5C Teleki, 3309 Couderc (3309C), Merbein 5489, Merbein 6262, Merbein 5512, C20, C29, C113, and C114, with own-rooted vines acting as the control group. Berries were collected at harvest in the 2020 and 2021 vintages for small-scale winemaking. The pH, titratable acidity, phenolic content, and antioxidant activity of both the berries and wine were measured using conventional chemical analysis. The phenolic composition of the wine over the two vintages was identified and quantified by high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HPLC-QTOF-MS/MS) and HPLC with diode-array detection (HPLC-DAD). The volatile composition was measured by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Grafting Pinot noir onto 3309C caused a reduction in the berry and wine pH without affecting the titratable acid. Several rootstocks, such as 1103 Paulsen, SO4, Schwarzmann, and 5C Teleki, reduced the total phenolic content (TPC) in both the berries and wine of Pinot noir. Conversely, Merbein 5489 increased the berry and wine TPC by 15% and 63%, respectively, compared to ungrafted Pinot noir MV6. A similar tendency was also found in the condensed tannin content (CTC), where Merbein 5489 increased the berry and wine CTC by 35% and 112%, respectively, compared to ungrafted vines. Several rootstocks, such as 3309C and Merbein 6262, increased the wine anthocyanin content (especially malvidin 3-O-glucoside), which may contribute to enhanced colour intensity. The concentrations of several ethyl ester compounds in wine responsible for the fruity aroma, including ethyl hexanoate, ethyl octanoate, and ethyl butanoate, were significantly higher in scions grafted to Schwarzmann, 3309C, Merbein 5489, and C29, compared to scions grafted to 101-14 Mgt, 1103 Paulsen, and ungrafted vines. This suggests that rootstock plays an important role in altering the texture and flavour of Pinot noir wine. Conclusions. Grafting Pinot noir to any rootstock in this study caused changes in the phenolic and volatile content of Pinot noir wine, likely affecting the perceived wine quality. Wine from Pinot noir grafted onto Merbein 5489, in particular, with relatively high CTC and anthocyanin content, as well as higher concentrations of volatile compounds contributing to the fruity aroma, represents an attractive option for grafting Pinot noir MV6 in cool climates. Significance of the Study. The present study provides results reflecting the impacts of grapevine rootstocks on Pinot noir berry and wine composition, supporting rootstock selection for Pinot noir. The findings offer guidance to vignerons in choosing suitable rootstocks to manage berry and wine acidity, phenolic accumulation and composition, and volatile profile, thereby improving the wine quality. Furthermore, the results could guide future studies in understanding the roles of rootstocks in regulating the metabolic pathways of phenolic and volatile production in the berries of grafted Pinot noir at the molecular level.