Effects of Basal Leaf Removal and Cluster Thinning on Monoterpene Accumulation and the Expression of Terpene Biosynthesis Genes in Ripening Moscato Bianco Grape Berries

Monoterpenes are key contributors to the aromatic profile of Moscato Bianco grapes and wines. In recent years, producers in the Asti DOCG area (northwestern Italy) have reported a decline in grape aromatic intensity. This study aimed to evaluate whether canopy management practices, basal leaf removal and cluster thinning, can modify bunch‐zone microclimate and influence monoterpene biosynthesis and accumulation in Moscato Bianco berries. Field trials were conducted over two growing seasons in two vineyards located at different altitudes: Arione (higher altitude) and Vignaioli (lower altitude). Three treatments were applied: (a) basal leaf removal at post‐berry set (BBCH 71–73), (b) basal leaf removal at veraison (BBCH 81–85) and (c) cluster thinning at veraison (BBCH 81–85). Grapes were collected at two ripening stages corresponding to commercial harvests for Asti spumante (T1) and Moscato d’Asti (T2). Pulp and skin tissues were analysed separately for free and bound monoterpenes using GC‐MS, and the expression of terpene biosynthesis genes was assessed via RT‐qPCR. Microclimatic conditions around clusters were monitored using sensors recording temperature and light intensity data. Leaf removal significantly altered bunch‐zone irradiation, with moderate effects on temperature. Terpene synthase (TPS) gene expression showed important treatment‐dependent fluctuation. VvTER expression was significantly reduced at T2 across vineyards and tissues. In Vignaioli, basal leaf removal and cluster thinning at veraison significantly increased monoterpene accumulation, especially at T2 and most strongly in the glycosylated fraction. In Arione, treatment effects were less pronounced at T1 and showed limited benefits at T2. Cluster thinning and basal leaf removal at veraison may help preserve the characteristic aromatic profile of Moscato Bianco grapes under variable and changing climatic conditions.