Enhancement of anthocyanin and chromatic profiles in ‘<scp>Cabernet Sauvignon’</scp> (<scp><i>Vitis vinifera</i></scp> L.) by foliar nitrogen fertilizer during veraison

Abstract BACKGROUND The influence of foliar nitrogen fertilizer during veraison (FNFV) on anthocyanin accumulation and chromatic characteristics of ‘Cabernet Sauvignon’ grapes over two seasons was investigated. RESULTS Urea and phenylalanine fertilizers (TU and TP, respectively) and a control were sprayed three times at veraison. In 2018, TU displayed a significant enhancement in total individual anthocyanin content and a * and C ab * profiles. In 2019, FNAV significantly improved the content of total non‐acylated, acylated anthocyanin and total individual anthocyanin, and the profiles of L* , a* and C ab * , except a* in TU. The whole process from phenylalanine variation to anthocyanin accumulation in grape skins was analyzed. On the whole, after the first FNFV to harvest, the increase in phenylalanine metabolism, abscisic acid content, effects of PAL (Phenylalanine ammonia lyase), UFGT (UDP glucose‐flavonoid 3‐O‐glucosyltransferase) and transcript concentrations of VvPAL and VvUFGT involved in anthocyanin biosynthesis were also strong evidence explaining the increased anthocyanin and chromatic profiles in 2019. CONCLUSION Overall, FNFV for nitrogen‐deficient grapevines could significantly improve grape color, especially in the 2019 veraison with a proper climate. © 2021 Society of Chemical Industry.