## 1 Introduction  
China has become one of the world's leading grape-producing countries, with an annual grape yield of 12.6 million tons in 2014 [1]. Eighty percent of its grapes are table grapes that are normally eaten fresh by customers. Additionally, 15% of the total grape yield is used to produce wine, while grape raisins are made from 5% of the total grape output [2]. Regarding table grapes, their berry size, appearance, texture, and sensory attributes play an essential role in determining the market value and acceptance of customers. It has been confirmed that these nutritional parameters of table grapes are affected by grape genetic backgrounds [3; 4; 5], cultivation conditions [6; 7; 8], post-harvesting operations [9; 10], and packaging treatments [11; 12].  
The overall aroma of fruits has been confirmed to be determined by the volatile composition [13; 14; 15; 16]. It has been reported that grape berries contain numerous volatile compounds. Among these volatile compounds, C6 volatile compounds exist as one of the major volatile compounds in grape berries and other fruits [17; 18; 19; 20]. These volatiles have been reported to exhibit vegetable, fresh, green, fruity, almond, apple, or minty scents [21; 22].  
Biologically, the biosynthesis of C6 volatile compounds in fruits results from oxylipin metabolism under the activity of lipoxygenase (LOX), hydroperoxide lyase (HPL), alcohol dehydrogenase (ADH), and alcohol acetyltransferase (AAT) in the LOX/HPL pathway [23]. The composition and distribution of C6 volatile compounds in grape berries is determined by grape germplasm, cultivar, climate, soil, vintage, and cultivation management [14; 17; 24; 25; 26; 27]. For instance, it has been reported that alteration of the microclimate, such as light exposure duration and water conditions, could inhibit or stimulate the expression of the LOX/HPL-pathway-related genes, which further results in alteration of the activity of C6 volatiles' synthesis-related enzymes. As a result, C6 volatiles' accumulation in grape berries could be significantly altered [28; 29; 30]. Such investigations have been well studied in wine-making grape cultivars. However, few studies were focused on table grape cultivars, to our best knowledge. Therefore, this study was designed to investigate C6 volatiles' accumulation and related gene expression in table grape berries, with the aim of improving table grape berries' quality. To this end, we selected seven cultivars of _Vitis vinifera_ table grape berries, including \"Xiangfei\", \"Moldova\", \"Tamina\", \"Italia\", \"Zaomeiguixiang\", \"Muscat of Alexandria\", and \"Christmas Rose\" in two consecutive vintages (2013 and 2014). These cultivars are mainly cultivated as table grapes in China, and they possess different sensory features. In each vintage, the C6 volatiles composition of each cultivar from veraison to harvest was studied using solid-phase microextraction (SPME)-gas chromatography/mass spectrometry (GC/MS). More importantly, unlike other studies [31], the concentration of the C6 volatile compounds in these cultivars was absolutely quantified with their standard in the present study. Meanwhile, the expression of the LOX-HPL-pathway-related genes in these cultivars (except \"Moldova\" and \"Italia\") in the 2014 vintage was assessed using the real-time qPCR technique. The findings from this study could elucidate the contribution of the C6 volatile composition to the aromatic features of table grape berries, and further establish the correlation of the C6 volatiles' accumulation with the critical genes in table grapes during berry development stages.