Influence of Pre-Harvest Application of Benzothiadiazole on Color and Aroma of Cabernet Gernischt Grapes During Fruit Development
[Objective]This study aimed to investigate the impact of benzothiadiazole(BTH)on the expression of pigments and related genes in grapevines during fruit ripening,and to elucidate its influence on the composition and concentration of free and bound volatile compounds,thereby exploring the underlying mechanisms of BTH in regulating anthocyanin and aroma biosynthesis in grape berries.[Method]Wine grapes Cabernet Gernischt were used as test material,and the whole grapevine was sprayed with 0.37 mmol·L-1 BTH solution containing 0.1％Tween 80 at the swelling period.A control group(CK)was sprayed with an equivalent solution of Tween 80 alone.The impact of BTH treatment on grape quality was evaluated by measuring chlorophyll,carotenoids,total anthocyanins,total proanthocyanidins and anthocyanin,as well as changes in concentration and composition of free and bound aroma in grapes.[Result]BTH application notably decreased chlorophyll a,b,and total carotenoid content while enhancing total proanthocyanidins,anthocyanins,and color index of red grapes,thus facilitating grape color development.In addition,BTH significantly upregulated the expression of anthocyanin synthesis-related genes,including VvCHS1,VvF3H1,VvDFR,VvLDOX,VvUFGT,and VvMYBA.It also significantly decreased the content of free and bound C6/C9 compounds,free straight-chain aliphatic compounds,free branched aliphatics compounds,but increased bound straight-chain aliphatic compounds,free and bound aromatic compounds,bound branched aliphatic compounds,free and bound terpenes,and free and bound norisoprenoids concentrations.By defining qualitative and quantitative biomarkers for grape ripening stages,it was found that aroma evolution from two adjacent developmental stages was markedly different,and BTH significantly influenced the trend of aroma evolution in both free and bound.BTH significantly altered the trend of free aroma at 9 weeks post-flowering(wpf)and 11 wpf as well as in the bound aroma of 11 wpf.The six major categories of aroma,free C6/C9 compounds,straight-chain aliphatic compounds,and terpenes,and bound C6/C9 compounds,straight-chain aliphatic compounds,and terpenes,were the major contributing components that differentiated aroma performance between CK and BTH grapes.A total of 23 active aroma components including 3-hexenal and β-ionone were identified by using the odor activity value＞0.1 as threshold.BTH mainly attenuated the vegetal and fatty flavors of grapes and enhances the floral and fruity odors.[Conclusion]BTH promoted grape coloration and changed the aroma content and composition by altering expression pattern of chlorophyll,carotenoid,anthocyanin synthesis and related genes,which in turn improved the quality of grapes.
wine grapeCabernet Gernischtbenzothiadiazolearomacolorripening process
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