Canopy management shapes grape and wine quality: Effects of canopy height on phenolic composition and volatile metabolome.

Canopy management is an important viticultural practice for regulating fruit-zone microclimate and quality formation. This study evaluated the effects of four canopy heights (80, 110, 140, and 170 cm) on canopy microclimate, photosynthetic performance, berry ripening, phenolic composition, and wine quality in 'Petit Verdot' grown in the eastern foothills of the Helan Mountains, Ningxia, China. Increasing canopy height reduced fruit-zone photosynthetically active radiation and diurnal temperature range, while increasing relative humidity. The intermediate canopy heights (PV110 and PV140) were associated with favorable photosynthetic performance and promoted berry ripening, with PV140 exhibiting the highest activities of dihydroflavonol 4-reductase and UDP-glucose:flavonoid 3-O-glucosyltransferase. Accordingly, PV140 wines showed higher levels of total flavonoids, flavan-3-ols, and total anthocyanins, together with greater red intensity and color saturation. Untargeted HS-SPME-GC-MS analysis annotated 1035 volatile metabolites, of which 165 were significantly responsive to canopy height; terpenoids, esters, and alcohols were the predominant classes among the differential metabolites. Correlation analysis further revealed coordinated associations among canopy structural parameters, fruit-zone microclimate, photosynthetic performance, anthocyanin biosynthesis, phenolic composition, and wine volatile metabolites. Overall, under the conditions of this study, a canopy height of 140 cm was associated with favorable 'Petit Verdot' berry ripening, greater anthocyanin accumulation, enhanced wine color attributes, and distinct volatile metabolite profiles. These findings provide a basis for further evaluation of precision canopy management under similar viticultural conditions.