## 2 Results and Discussion
### Varietal Effect on the Concentrations of GLVs in Grape Berries by Multivariate Analysis  
To interpret the variations of GLVs in the four cultivars, partial least squares-discriminate analysis (PLS-DA) was performed by Metabo-Analyst 3.0 [30] on the subset of normalized data of 2010 and 2011 vintage. As displayed in Figure 2A,C, these cultivars were separated from each other, especially Syrah grape. From the Figure 2B, (\(Z\))-3-hexen-1-ol, hexanol and (\(Z\))-3-hexenyl acetate with a Variable Importance in Projection (VIP) score over 1, contributed to the discrimination of these varieties by first principal component in 2010 vintage. However, (\(E\))-2-hexen-1-ol, hexyl acetate, hexanal, (\(E\))-2-hexen and (\(Z\))-3-hexen-1-ol were the main C6 compounds discriminating Syrah, Muscat Tchervine and Gewurztraminer grapes in 2011 vintage (Figure 2D). Figure 1: Heat maps of green leaf volatiles (GLVs) of different varieties in 2010 and 2011 vintages. The left of each colored square represent 17, 31, 43, 59, 73, 87, 101 and 106 days after flowering (DAFs) in 2010 vintage, and the right of each square represent 33, 48, 69, 75, 89, 102 and 112 DAFs in 2011 vintage, respectively. * indicates the veraison stage. LOX, lipoxygenase; HPL, hydroperoxides lyase; ADH, alcohol dehydrogenase; AAT, alcohol acyl transferases; Syrah (Syr, neutral red cultivar); Muscat Tchervine (MT, Muscat cultivar); Gewurztraminer (Gew, non-Muscat aromatic cultivar); Chardonnay (Char, neutral white cultivar). It can be observed from the bar diagrams (Figure 3) that Syrah berries contained higher concentrations of C6 aldehydes than Muscat Tchervine grapes in both growing seasons. In the 2010 vintage, the concentration of C6 aldehydes of Syrah berries was slightly higher than those of Gewurztraminer and Chardonnay. However, no statistical difference was observed in the 2011 vintage. Regarding C6 alcohols, Muscat Tchervine had relatively higher C6 alcohols than Gewurztraminer in both vintages. Besides, the concentrations of C6 esters in Muscat Tchervine were higher than the other varieties. As we knew, Muscat Tchervine and Gewurztraminer are two aromatic white wine grape cultivars. Terpenes are considered as the most important volatile components determining aroma quality of aromatic varieties. These compounds can provide floral and sweet fruity aroma for the final wine products [14,31]. Until now the reports remain limited regarding the variation and influence of lipid-derived volatiles with green or fruity odor in aromatic grape varieties. Moreover, the effects of lipid-derived volatiles on the grape and wine aroma presentation are also poorly understood even though these C6 volatiles can be detected at a considerable amount in Muscat Tchervine and Gewurztraminer wines [32,33]. The interaction between these compounds contributing to different sensory attributes needs to be investigated. There are several other reports on varietal differences in terms of C6 compounds. It has been demonstrated that Chardonnay skins contained higher amounts of (\(E\))-2-hexenal and hexanol than Airen and Macabeo grapes, and Airen grape had the highest level of (\(Z\))-3-hexen-1-ol and the lowest level of hexanal and (\(E\))-2-hexenal [29]. C6-acetates were considered as the most importantly influenced volatile esters in Shiraz and Cabernet Sauvignon grapes and wines,  
Figure 2: Partial least squares discriminant analysis (PLS-DA) of GLVs from harvested grape berry of different varieties in two vintages. (**A**,**C**) Score plot of 2010 and 2011 respectively; and (**B**,**D**) selected compounds based on Variable Importance in Projection (VIP) scores of 2010 and 2011 respectively. and a more active LOX pathway in Shiraz grape was suggested then [20]. Thus, based on the results obtained in this work together with previous reports, we concluded that the C6 compounds are also important constituents of varietal typicality.