The effects of the severity and timing of leaf removal (LR) on the amino acids of Sauvignon Blanc grapes and wines were studied during the 2017 growing season.  High-performance liquid chromatography (HPLC) was used to analyze the amino acids profiles of grape berries and wines.  The basal leaves were removed at three time points (40, 56 and 72 days after flowering, named LR40, LR56 and LR72, respectively) at two severity levels (one at which the first, third, and fifth basal leaves of each shoot were removed (50% level); and another at which the first six basal leaves were removed (100% level)).  The results showed that leaf removal had little impact on total soluble solids (°Brix), titratable acidity, pH or berry weight.  The LR72-50% treated grapes had higher berry weight, titratable acidity and °Brix than those of the other treatments.  The highest concentrations of total amino acids and of total amino acids except proline were detected in LR72-50% treated grapes (2 952.58 and 2 764.36 mg L^–1, respectively); the lowest were detected in LR72-100% treated grapes (2 172.82 and 2 038.71 mg L^–1, respectively).  LR72-50% treatment significantly promoted the synthesis of aspartic acid, serine, arginine, alanine, aminobutyric acid and proline at both severity levels for grapes, the concentrations of all of these amino acids were increased relative to the control concentrations.  The LR72-50%, LR40-100% and LR72-100% treated wines had higher total amino acids concentrations and higher concentrations of some individual amino acids, such as arginine, alanine and serine, than did the control wines.  Of all the amino acids studied, glycine, tyrosine, cysteine, methionine and lysine were not significantly influenced by the timing or severity basal defoliation in grapes and wines.  The present study reveals the effects of the timing and severity of leaf removal on the amino acids profiles of grapes and wines.

Leaf removal and cluster thinning were carried out prior to veraison to evaluate the effects on berry quality of two Vitis vinifera cultivars (Cabernet Sauvignon and Ugni Blanc) in the Weibei Dryland of China in 2013 and 2014, and comprehensive analysis of the chemical and volatile composition in berries was performed.  The results showed that content of reducing sugar in both varieties was not affected while total acid was generally decreased by leaf removal and cluster thinning.  The pH of berry juice was correspondingly higher in most treatment groups.  Meanwhile, promoting effects on accumulation of total phenols, tannin in both varieties and total anthocyanins in Cabernet Sauvignon were found.  As for monomeric anthocyanins, percentage of malvidin and its derivatives was decreased by leaf removal and cluster thinning.  Besides, cinnamylated anthocyanins decreased with the intensity of cluster thinning.  The accumulation of non-anthocyanin phenolics was similarly affected in the two varieties.  Notably, cluster thinning was more effective on enhancing the phenolics content than leaf removal.  The combination of middle level of leaf removal and cluster thinning was the most favor to the accumulation of phenolic acids.  Furthermore, cluster thinning could also significantly enhance the synthesis of flavanols and stilbenes.  Lastly, content and variety of aroma compounds in both grape varieties were also significantly affected by the treatments.  The results provided a theoretical basis for a combination of leaf removal and cluster thinning to improve quality of grapes and wines.