Shading Nets Modified Cluster-Zone Radiation, Bunch Sunburn Percentage and Berry Amino Acid Content in Cabernet Sauvignon: A Preliminary Study

Shading nets are increasingly used in warm-climate vineyards to mitigate excessive cluster exposure. However, relatively few studies have evaluated their effects on fruit-zone microclimate and berry composition. This single-season field study evaluated the effects of conventional and photoselective shading nets in Cabernet Sauvignon on cluster-zone radiation, thermal conditions, bunch sunburn and powdery mildew percentage, berry maturity, and free amino acid content. Shading treatments significantly modified incident photosynthetically active radiation in the bunch zone, while air-temperature-derived thermal indices were not significantly affected. The conventional black Raschel net produced the greatest reduction in incident radiation, but this reduction was not associated with a decrease in sunburn or powdery mildew severity in bunches. The gray–pearl photoselective net maintained intermediate radiation levels and showed a lower severity of sunburn and powdery mildew, together with higher must pH and lower berry arginine content. The black–white photoselective net reduced berry soluble solids, while the conventional Raschel net increased berry histidine content, indicating that berry maturity and amino acid responses were treatment-dependent. These results provided preliminary field evidence on the effects of shading nets on Cabernet Sauvignon bunch sanitary and berry composition. Therefore, further multi-season and multi-site studies are needed before broader recommendations on shading-net use in warm-climate vineyards.