Dynamic light exposure from afternoon shading reveals aromatic plasticity in grapes and wines from a semi-arid region

To mitigate afternoon heat stress and improve aroma attributes in semi-arid regions, Cabernet Sauvignon grapevines were subjected to moderate (MD, 1.5 h) and strong shading (SD, 2.5 h) treatments over three vintages (2021-2023). Plant responses to diurnal light dynamics were assessed, berry and wine volatiles were analyzed, and wine sensory was evaluated. Results showed that photosynthetic assimilation of grapevines was suppressed by 50% during shading, while photosynthesis during exposure and leaf area were enhanced. Berry volatiles in MD and SD were 16% and 10% lower than CK at 2021 harvest, but were enhanced in the latter two years. Linalool, hexanal, β-damascenone, and 6-methyl-5-hepten-2-one were key light-responsive biomarkers. Shaded wines exhibited elevated levels of terpenoids and norisoprenoids, contributing to improved fruity-floral aromas and sensory scores in 2022 and 2023. This study provides new insights into grapevine responses to light modulation and the volatile modification of grape and wine under semi-arid conditions.