## 2 Results and Discussion
### Effects of Rootstocks on Berry Volatile Compounds  
There were 99 volatile compounds identified in grape berries during grape development in the two seasons (Supplementary Table S2). The O2 PLS-DA (bidirectional orthogonal partial least squares discriminant analysis) strategy was applied to each rootstock and own-rooted vines (eight comparisons) in order to overcome the season effects and solely investigate the influence of each rootstock on volatile metabolites. In each O2 PLS-DA model, a seven-fold internal cross-validation was conducted to validate the reliability of the model. The \(R^{2}Y\) and \(Q^{2}Y\) obtained from cross-validation measure the goodness of fit and the predictive ability of the O2 PLS-DA model, respectively. Besides, a \(p\)-value was calculated in the cross-validation procedure (\(p_{\text{CV-ANOVA}}\)) to estimate the significance of the O2 PLS-DA model. Quality parameters of \(Q^{2}Y\) above 0.5 and \(p_{\text{CV-ANOVA}}\) below 0.01 were set as thresholds to identify acceptable models. In addition, 500 permutations were performed to avoid overfitting of the O2 PLS-DA model. Variable importance in projection (VIP) ranks the contribution of each variable to the O2 PLS-DA model, and variables with VIP > 1.0 were considered as having the highest discrimination potential. Statistical differences in concentrations of volatile compounds between each rootstock and CS were determined according to the student's \(t\)-test (\(p<0.05\)) at each  
Figure 3: Effects of each rootstock on anthocyanins in two seasons (2015–2016). Each data represent the log2 fold change of anthocyanin content/proportion in berries on each grafted vine relative to those on own-rooted vines. ‘Total’, the concentration of total anthocyanins; ‘\(\sum\)’, the total concentration of different fractions of anthocyanins; ‘\(\infty\)’, the proportions of different fractions of anthocyanins; ‘Cy’, cyanidin; ‘Pn’, penoidin; ‘Pt’, petunidin; ‘Dp’, delphinidin; ‘Mv’, malvidin; ‘Glu’, anthocyanins in glucoside form; ‘Ace’, acetylated anthocyanins; ‘Cou’, coumarylated anthocyanins; ‘Caff’, caffeoylated anthocyanins; ‘Met’, methoxylated anthocyanins; ‘3 OH’, 3’-hydroxylated anthocyanins; ‘35 OH’, 3’\(\leq\)’\(\leq\)’hydroxylated anthocyanins. The asterisk * in each bar indicates significant differences between grafted and own-rooted vines in the same season at the basis of student’s \(t\)-test at \(p<0.05\). developmental stage. Through these criteria, those volatile compounds being consistently affected by rootstocks during development or at a certain developmental stage in the two seasons were characterized as volatile biomarkers. Obtained O2 PLS-DA models, except CS/Harmony vs. CS and CS/5A vs. CS, showed the clear separation between the grafted and own-rooted vines (Supplementary Figure S3). Values of \(R^{2}Y\), \(Q^{2}Y\), and \(p_{\text{CV-ANOVA}}\) of these O2 PLS-DA models indicated excellent fit and predictive abilities, as well as the high significance of models (Table 3). In addition, 500 permutation tests of each O2 PLS-DA model demonstrated that the predictive ability of the original model (\(R^{2}Y\), \(Q^{2}Y\)) was higher compared to the permutated model (Supplementary Figure S3). Therefore, these O2 PLS-DA models were reliable for discovering aromatic biomarkers of the grafted vines. Through O2 PLS-DA analysis, CS/Harmony and CS/5A were not discriminated from own-rooted vines using volatile compounds, suggesting that CS/Harmony and CS/5A had no obvious influence on the accumulation of volatile compounds in this study. Through O2 PLS-DA analysis, 26 volatile compounds with VIP > 1.0 were characterized to separate CS/101-14 from CS (Supplementary Table S3). Among these compounds, 101-14 had a positive influence on benzyl alcohol concentrations from E-L 31 stage until E-L 37, especially at E-L 35.5 and 36 stage, when 101-14 increased the concentration of benzyl alcohol significantly more than CS. At harvest, 101-14 slightly increased the concentration of benzyl alcohol in 2015, while the reverse was observed in 2016.