Leaf area/crop weight ratios of grapevines: Influence on fruit composition and wine quality

The fruiting capacity of grapevines in a given climatic region is largely determined by their total leaf area and by the percentage of the total leaf surface area that is exposed to full sunlight, provided other factors are not limiting growth and the initiation of fruit primordia. A wide range of leaf area/crop weight ratios were investigated by pruning to different levels of buds per vine, by different degrees of defoliation, and/or by cluster thinning of grape cultivars Thompson Seedless, Tokay, Chenin blanc, and Cabernet Sauvignon located at Davis or Oakville, California. For single-canopy (SC) type trellis-training systems, the leaf area/crop weight ratio required for maximum level of total soluble solids, berry weight, and berry coloration at harvest ranged from 0.8 to 1.2 m(2)/kg, whereas for horizontally divided-canopy (DC) type trellis-training systems (GDC, lyre, wye), this ratio was reduced to 0.5 to 0.8 m(2) leaf area per kg fruit. Optimal crop yield/pruning weight, pruning weight (kg) per m canopy length, leaf area (m(2)) per m canopy length, and leaf area density (m(2)/m(3)) for SC systems ranged from 4.0 to 10, 0.5 to 1.0 kg/m, 2 to 5 m(2)/m, and 3 to 7 m1m-1, respectively. Similarly, for DC systems these ratios ranged from 5.0 to 10, 0.4 to 0.8 kg/m, 2 to 4 m(2)/m, and 3 to 6m(2)m(-3), respectively. Grapevines with ratios that fell within the ranges given above for each of these five parameters were considered well balanced and capable of producing high-quality fruit and wines.