###### Abstract  
Rootstocks were bred and selected from several species in order to enhance the resistance against biotic or abiotic stresses. There are few studies on the effect of rootstocks on aroma and related gene expression. This study focused on the effects of three rootstocks, Kober 5 BB (5 BB), 1103 Paulsen (1103P), and Selection Oppenheim (SO4), on the aroma and volatile-related gene expression levels of Merlot and Marselan berries and wines. These three rootstocks reduced the total aroma content of Merlot wine. 5 BB upregulated _VvLoXA_ and showed increased C6 alcohols. 1103P enhanced the linalool from Merlot berry, with marked upregulation of _VvLinNer1_. Conversely, rootstocks increased the total aroma content of Marselan berry, verified by the related expression levels of volatile-related genes. For Marselan berry, 5 BB and 1103P upregulated five _VvGTs_ and nine genes from the LOX and MEP pathway. 1103P increased the contents of C6 alcohols, C6 aldehydes, and citronellol from Marselan berry. Compared to 5 BB and SO4, rootstock 1103P provided berries of better quality and richer aroma volatiles to Merlot and Marselan, while all three of the rootstocks had a significant effect on scion-rootstocks. scion-rootstock; volatile-related gene expressions; C6 compounds; LOX pathway +
Footnote †: journal: _foods_  
0000-0002-319-2277-10000-0000-0000-00000-000  
which are mostly formed via the mevalonic acid (MVA) pathway, the plastidial methyleryth-thiritol phosphate (MEP) pathway, and the lipoxygenase (LOX) pathway [12]. The MEP pathway, localized in plastids, synthesizes isopentenyl pyrophosphate (IPP) and dimethylally pyrophosphate (DMAPP) from pyruvate and glyceraldehyde 3-phosphate (G3P) via 1-deoxy-D-xylulose-5-phosphate synthase (DXS), 1-deoxy-D-xylulose 5-phosphate reductase isomerase (DXR), 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR), etc. The MVA pathway, which occurs in the cytosol, brings acetyl-CoA into IPP and DMAPP [13]. These two isomeric five-carbon precursors generate GPP, FPP, GGPP, and \(\beta\)-carotene. Ternpenes (monoterpenes, sesquiterpenes, and diterpenes) are synthesized by terpene synthase based on GPP, FPP, and GGPP, while \(\beta\)-carotene ulteriorly formed norisoprenoids precursor. Norisoprenoids, derived from the oxidative breakdown of carotenoids, which consist of GGPP, are the dominant volatile compounds of neutral cultivars, whereas terpen contribute aroma mostly to muscat/floral cultivars [14]. The lipoxygenase pathway, the primary aroma source of non-muscat grapes, generates C6 and C9 volatile compounds from linoleicc/linolenic acid via lipoxygenase (LOX), hydroperoxides (HPL), alcohol dehydrogenase (ADH), and alcohol acyltransferases (AAT). The factor impacting grape volatiles is diversity, which depends on cultivar, soil, weather, water, training and canopy management, fertilization treatment, etc. [15]. Different cultivars have different characteristic grape aromas, such as 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) for Riesling and terpenes for Muscat cultivars. [PERSON] et al. [16] found Tramiente to have different aroma compounds between the cool site and the hot site and the cool site to have higher 6-carbon aldehydes and the hot site to have higher monoterpenes. [PERSON] et al. (2019) suggested that rootstock SO4 is not recommended because the cabernet sauvignon berries grafted onto SO4 have a lower concentration of total esters compared to berries from own-rooted samples, while 101-14, Ganzin 1, 110R, and 5 BB increase the concentrations of C13-norisoprenoids [17]. [PERSON] et al. (2020) reported that rootstocks 99R, 140 Ru, 110R, 1103P, and Gravesac lead to a higher content of total ethyl esters in Merlot wines, while the own-rooted wines have the lowest content of (E)-3-hexenol and total ethyl esters [18]. In vineyards, grafting is a common cultivation method. Nonetheless, there are few studies on the effect of rootstocks on aroma and related gene expression.