Effects of Training System On Sunlight Penetration, Canopy Structure and Fruit Characteristics of ‘Frontenac' (Vitis spp.)

Trellises or training systems influence many aspects of grapevine growth and production. This study investigated the effects of 5 trellis styles on the fruit-zone light environment, fruit chemical composition and yield of ‘Frontenac’ grapes grown on a highly fertile site near Crete, Nebraska. Photosynthetically active radiation (PAR) was measured with a line quantum sensor (Li-Cor Inc., Lincoln, NE) both above the canopy and within the fruiting zone at 3 stages of fruit development (berry set, veraison, and harvest) from which percent transmittance was calculated. Point quadrat canopy analysis was performed at veraison; data were used to compute leaf layer number (LLN). Fruit was collected at harvest for chemical analysis (pH, per cent soluble solids, titratable acidity). At all sampling dates, vines grown on Geneva Double Curtain (GDC) and High Cordon (HC) trellises had significantly higher mid-day transmittances than vines grown on Smart Dyson (SD) and Vertical Shoot Positioned (VSP) training systems. LLN was lower for GDC and HC than for SD and VSP. GDC vines had higher fruit yield (2.4 kg per plant) than VSP, SD, HC, and Scott Henry (1.3, 1.3, 1.1, and 0.9 kg per plant, respectively). Yields for all trellis styles were lower than expected due to wind damage early in the season. GDC fruit had higher pH and soluble solids than fruit from other trellises; titratable acidity was lower in GDC and HC fruit than in SD and VSP fruit. GDC and HC canopies had the highest (most favorable) transmittance values, but GDC vines yielded significantly more and better quality fruit. These results suggest that GDC is the best training system for ‘Frontenac’ on high vigor sites in southeastern Nebraska.

Additional index words: trellis, grape, PAR, microclimate, fruit quality