On December 15, 2020, the team of Professor Fang Yulin of the Wine School published a cover article entitled”Foliar Phenylalanine Application Promoted Antioxidant Activities in Cabernet Sauvignon by Regulating Phenolic Biosynthesis” in the Journal of Agricultural and Food chemistry. Cheng Xianghan, a 2017 doctoral student of the School of Wine, is the first author, and Professor Fang Yulin and young teacher Sun Xiangyu are the co-corresponding authors.
This study found that in low-nitrogen vineyards, applying phenylalanine fertilizer to grape leaves during the color conversion period can increase the antioxidant activity of the fruit by promoting the biosynthesis of Cabernet Sauvignon phenolics.
Oxidative stress is related to the formation of certain human diseases. The phenolic components in grapes and wine have antioxidant properties that can offset the negative effects of oxidative stress, making wine more and more popular with consumers. Therefore, wine grape growers have been seeking cultivation measures that can increase the phenols in the fruit to further improve the quality of the wine. The color transition period is the boundary between vegetative growth and reproductive development. During this period, a small amount of nitrogen fertilizer is added to the grape leaves, which will not affect the vegetative growth of the plant, but will increase the phenolic substances of the grape fruit in the low-nitrogen vineyard.
This experiment studied the effect of foliar phenylalanine application during veraison (FPV) on the biosynthesis of grape phenols and the relationship between phenolic components and antioxidant activity during the color transition period. During the color change period, 69 and 138 mg N/plant of phenylalanine (Pe1 and Pe2) and a nitrogen-free blank aqueous solution (CK) were sprayed three times. And the experiment was carried out in the field and greenhouse sand culture at the same time, and it was found that FPV can significantly improve the antioxidant activity of grapes. Compared with CK, anthocyanins and stilbene compounds are the phenolic components that have the greatest impact on antioxidant activity after FPV treatment. From the first FPV application to the harvest period, the metabolic level of the precursor substance phenylalanine in the phenolic synthesis pathway, the content of abscisic acid and the expression levels of VvPAL, VvCHS, VvF3H, VvUFGT and VvSTS all increased. Although Pe2 significantly increased the total phenol content of grapes compared with Pe1, the dosage of phenylalanine did not significantly affect its antioxidant activity on fruits. In conclusion, our research shows that FPV is an effective nitrogen supplementation measure, which can increase the content of grape phenolic substances in nitrogen-deficient vineyards and increase its antioxidant activity.
link to the original text:https://dx.doi.org/10.1021/acs.jafc.0c05565