Using different rootstocks grafted'Crimson Seedless'grapes asexperimental material,with self-rooted seedlings as the control,this study investigates the effects of skin color,phenolics content,and enzyme activity related to its synthesis.The objective is to enhance the phenolics content,uneven coloring,thereby improving fruit quality of'Crimson Seedless'grapes through rootstock grafting.The results showed that the mature'Crimson Seedless'grapes grafted onto specific rootstocks exhibited a red coloration.Both grafting and self-grafting with rootstocks 101-14 and 110R resulted in reductions of L*,b*values,and increased a*,while SO4 with rootstocks decreased L*and b*.Furthermore,grafting with rootstocks 101-14 and 110R significantly promoted the accumulation of soluble solids in grape fruits and reduced their titratable acid content.Grafting with rootstocks promoted the accumula-tion of phenolics in'Crimson Seedless'grapes to varying extends.At maturity,grafting with root-stocks 101-14,110R,SO4,and self-grafting led to significant increase in total phenols,flavonoids,and anthocyanins.Among them,the total phenols,flavonoids,and anthocyanins of'Crimson Seedless'grafted onto rootstocks 101-14 were significantly increased by 50.88％,52.00％and 74.13％com-pared to the control,respectively,demonstrating the most pronounced enhancing effect.Compared with the control,grafting on rootstock 101-14 was most effective in improving the activity of phenolics compound synthesis-related enzymes in'Crimson Seedless'grapes.In contrast,grafting onto root-stock SO4 did not significantly enhance the activities of DFR and UFGT enzymes.Correlation analysis shows a strongcorrelation between phenolics in the fruit peel of rootstock-grafted seedlings and DGR and UFGT activities,and their combined effects affect the changes in phenolics.The results demon-trate that rootstock grafting promotes the coloration of the grape peel of'Crimson Seedless'grapes.Rootstock 101-14,110R,SO4 grafting,and self-grafting can promote the activity of DFR and UFGT,increase the content of phenolics in the peel.Among these,rootstock 101-14 performs best.
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