The beneficial effect of leaf removal during fruit set on physiological, biochemical, and qualitative indices and volatile organic compound profile of the Cypriot reference cultivar 'Xynisteri'

Background 'Xynisteri' is the reference Cypriot white cultivar that, despite its significant societal and economic impact, is poorly characterized regarding its qualitative properties, while scarce information exists regarding its aroma profile. In the current study, the effect of leaf removal during fruit set (BBCH 71) on 6-year cordon-trained, spur-pruned grapevines was assessed and an array of physiological, biochemical, and qualitative indices were monitored during successive developmental stages (BBCH 75, BBCH 85, BBCH 87, and BBCH 89). Grapes were additionally monitored for the volatile organic compounds (VOCs) profile during the advanced on-vine developmental stages (BBCH 85-BBCH 89) with the employment of gas chromatography-mass spectrometry (GC-MS), Fourier-transform near infrared (FT-NIR) spectra and electronic nose (E-nose) techniques. Results Grape berries from the vines subjected to leaf removal were characterized by higher solid soluble sugars (SSC), titratable acidity (TA), tartaric acid, and ammonium nitrogen contents, while this was not the case for assimilable amino nitrogen (primary amino nitrogen). A total of 75 compounds were identified and quantified, including aliphatic alcohols, benzenic compounds, phenols, vanillins, monoterpenes, and C-13-norisoprenoids. Leaf removal led to enhanced amounts of glycosylated aroma compounds, mainly monoterpenes, and C-13-norisoprenoids. Chemometric analysis, used through FT-NIR and E-nose, showed that the aromatic patterns detected were well associated to the grape ripening trend and differences between leaf removal-treated and control grapes were detectable during fully ripe stage. Conclusion Leaf removal at fruit set resulted in an overall induction of secondary metabolism, with special reference to glycosylated aroma compounds, namely monoterpenes and C-13-norisoprenoids. (c) 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Automated summary

This study investigated the effects of leaf removal during fruit set on a Cypriot white cultivar and found that it led to an overall induction of secondary metabolism, particularly in glycosylated aroma compounds. The analysis of volatile organic compounds also showed differences between the leaf removal-treated grapes and the control group during the fully ripe stage.