## 2 Results and Discussion
### Varietal Effect on the Concentrations of GLVs in Grape Berries by Multivariate Analysis
In this work, the relative expression level of _VvLOXA_ in both Gewurztraminer and Syrah of 2010 was at least ten-fold higher than those in Muscat Tchervine and Chardonnay at harvest (Figure 4). Similarly, it expressed at a relative lower level in Muscat Tchervine compared with others in 2011 vintage. The lowest expression level of _VvLOXA_ in Muscat Tchervine was in line with its lowest concentration of C6 aldehydes. _VvHPL1_ of Chardonnay exhibited the highest expression level among these studied varieties in 2010 vintage, and when compared with Muscat Tchervine, Syrah grapes presented higher _VvHPL1_ expression. Similarly, _VvHPL1_ of Syrah in 2011 was expressed about eight-fold and five-fold higher than those of Gewurztraminer and Muscat Tchervine, respectively. Considering the fact that Syrah grape contained more abundant C6 aldehydes (Figure 3), we concluded that it was the higher expression level of _VvLOXA_ and _VvHPL1_ that led to the high accumulation of C6 aldehydes (Figure 4). In addition, the higher expression level of _VvAAT_ in Muscat Tchervine was in good agreement with its highest concentration of C6 esters in both vintages. [PERSON] et al. compared the volatile profiles of Cabernet Sauvignon and Shiraz wines, and suggested that enzymes in LOX pathway may have been more active in Shiraz grapes, thus leading to higher contents of C6 compounds [20]. Our present work supported this suggestion that varietal difference regarding green leaf volatiles should be predominately attributed to different expression level of LOX-HPL pathway genes. The Pearson's correlation was calculated with the data of metabolites and relative expression amount of each grape variety from all developing stages. These data were normalized in advance by scale method considering the wide range of the data. As seen in Table 1, the correlation coefficients between the accumulation of GLVs and the expression level of genes from LOX-HPL pathways varied greatly according to varieties. The production of volatiles of Syrah and Gewurztraminer grapes was significantly correlated with the expression of five genes, covering major enzymes in the LOX-HPL pathway; by contrast, in Muscat Tchervine grapes only _VvLOXO_, _VvHPL1_ and _VvAAT_ transcript abundances highly corresponded to the accumulation of volatiles. The expression of _VvLOXO_, encoding 13-LOX, was negatively correlated with the accumulation of (_E_)-2-hexenal in Chardonnay and Gewurztraminer grape berries, but positively correlated with the production of hexanal in Muscat Tchervine grape. We hypothesized that there possibly existed different regulation mechanisms for _VvLOXO_ in different varieties. In Muscat Tchervine grape, a significant correlation was observed between the relative expression of _VvHPL1_ and the concentration of (_E_)-2-hexenal. A positive relationship also existed between the expression level of this gene and the concentration of (_E_)-2-hexen-1-ol in Syrah grape. Regarding _ADH2_, it was observed to be positively correlated with (_E_)-2-hexenal production in Chardonnay and Gewurztraminer grape berries. In addition to the result that _AAT_ was positively correlated with C6 esters or alcohols in Muscat Tchervine and Syrah, the total concentration of C6 aldehydes was found to be negatively correlated with _AAT_ expression in Gewurztraminer, but the correlation was quite opposite in Chardonnay. To sum up, there existed the different correlations between gene expression of LOX-HPL pathway and concentration of C6 compounds among different grape cultivars. The biosynthesis of C6 compounds was complex and differential key genes determining GLVs production were presented in various grape varieties, which needed further research.