## 3 Discussion  
Although ABA was reported to increase the anthocyanin concentration in grapes by adjusting the anthocyanin biosynthesis pathway [16], this was not observed in wine from the current study using GRBV-positive vines. ABA impacts may depend on the grape variety, vineyard, vintage weather conditions, or timing of application. Regardless, the current results indicated that ABA application at veraison did not mitigate the negative effect of GRBV for anthocyanin in 2018 Pinot noir wine (Figure 1). Both levels of the monomeric anthocyanin and total phenolic content were lower in 2018 wines associated with ABA treatment than CON. The monomeric anthocyanin and total phenolic content were maintained with the application of ABA to GRBV-positive vines and no statistical difference was observed in either phenolic measurement in 2019. Inconsistent results across the two-year study did not allow for confident conclusions on the overall effect of ABA on the phenolic content in GRBD. The varying levels of anthocyanin in ABA treatment may result from the complex interaction between ABA and GRBV, of which the mechanism remains unclear. The volatile compounds which were statistically different between ABA treatments did not overlap between vintages, except for 2-phenylethanol and ethyl decanoate. Lower 2-phenylethanol and higher ethyl decanoate levels were found in ABA than CON in both years. As a higher alcohol, 2-phenylethanol can be formed through the amino acid metabolism majorly or glycosylated precursors during the vinvification process [32]. The production of higher alcohols was reported to be negatively related to the yeast-assimilable nitrogen (YAN) level [33; 34]. The grape basic chemical composition analysis showed higher YAN levels in GRBV-positive grapes under ABA treatment than in the unsprayed control [35]. In our study, the lower 2-phenylethanol level in the ABA treatment was in agreement with the high YAN in the berries. Typically, in Pinot noir grapes, C6-alcohols accumulate before veraison, but their levels decrease during berry ripening [36]. Moreover, ABA was reported to be able to increase the C6 compound accumulation by inducing the gene expression of alcohol dehydrogenase, which converts aldehydes to alcohols [37]. This effect of ABA was observed in this study, where an increase in two C6 alcohols ((E)-3-hexen-1-ol and 1-hexanol) was found in the 2018 ABA treatment. In this study, the results in 2018 showed that the ABA treatment increased the total concentrations of free-form C\({}_{13}\)-norisoprenoids, esters, and terpenes in GRBD wines (Table 2). Statistical differences in norisoprenoid compounds were only found in 2018. The ABA treatment caused a decrease in bound-form norisoprenoids (vitsiprane and TDN) and an increase in free-form norisoprenoids (\(\beta\)-damascenone and \(\beta\)-ionone). [PERSON] et al. found similar effects of exogenous ABA on free-form norisoprenoids over two vintages of Cabernet Sauvignon [38]. The ABA treatment had a large effect on volatile esters in 2019 GRBD wines, where a significant decrease was observed in eight esters. GRBD was reported to reduce the concentration of esters and terpenes in final wines [6]. In this study, ABA application did not obviously mitigate the effects of GRBV on esters and terpenes. The decrease in IBMP in 2019 indicated that ABA may have an impact on grape ripening. The IBMP content found in Pinot noir grape decreased with increasing grape maturity, with the greatest decline in IBMP occurring before veraison [39]. The analysis of phenolic compounds with HPLC (Table 1) showed no advantage to ABA application with regard to increasing the phenolic content of GRBD-affected wines. The effect of ABA on increasing the concentrations of phenolics diminished by GRBD was not observed. In fact, the opposite effect was observed with three compounds (caffeoyl-tartaric acid, malvidin-3-o-glucose, and trans-coutaric acid) decreasing in concentration across the two-year study.