Reduction of methoxypyrazines with ‘vegetable-like’ odors in grapes by foliar nitrogen application

Abstract

The influences of foliar nitrogen fertilizers on methoxypyrazines and the correlation between methoxypyrazines and amino acids in Cabernet Sauvignon were studied in nitrogen-deficient soil. Foliar urea and phenylalanine fertilizers (U and P, respectively), and CK were applied three times during veraison. Field trials in 2018 and 2019 revealed that nitrogen fertilizers could effectively increase leucine, valine and isoleucine in grapes and P was more effective than U in 2018. P significantly decreased methoxypyrazines in grapes and wines, thanks to effectively lower expression of VvOMT1, VvOMT2, VvOMT3 and VvOMT4 than other treatments, while U resulted in the highest content of methoxypyrazines among all treatments, due to the higher genes expression. A correlation analysis found that there was little correlation between the methoxypyrazines composition and their amino acid precursors in grapes. Our findings reveal that foliar phenylalanine fertilizer had the highest potential to weaken vegetable-like odors in wines from a nitrogen-deficient vineyard.