4750:
Canopy Light Environment Effects On Phenol and Flavonoid Content of ‘Frontenac' (Vitis spp.) Fruit
Thursday, August 5, 2010: 11:45 AM
Springs A & B
Christina M. Bavougian, M.S., Agronomy and Horticulture, University of Nebraska - Lincoln, Lincoln, NE
Vicki L. Schlegel, Associate professor, 5University of Nebraska – Lincoln, Lincoln, NE
In addition to their many functions within plants, polyphenols contribute greatly to the sensory attributes of wine, and provide many positive effects on human health. It is generally agreed that fruit shading reduces phenol concentrations in grapes and wine, but results have been inconsistent. This study was conducted to determine if the total phenolic and flavonoid contents of ‘Frontenac’ fruit are related to light intensity within the canopy. Four- and 5-year-old ‘Frontenac’ vines were trained to 5 different trellis systems on a fertile site near Crete, Nebraska. Photosynthetically active radiation (PAR) was measured with a line quantum sensor 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. 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. Fruit was collected at harvest for chemical analysis. Skins and seeds were separated from the berry pulp, dried in a vacuum oven, and extracted using a 50%:50% methanol:water solution for free phenolics and a 50%:50% methanol:water solution with 1.2 N HCl for bound phenolic compounds. Flavonoid and total phenol concentrations of the bound seed, free skin and bound skin extracts did not differ significantly among trellises. Within the free seed extract, SD had both a significantly lower total phenolic concentration than VSP and the upper canopy of Scott Henry (SH), and a significantly lower flavonoid concentration than VSP, GDC, and the lower canopy of SH. However, when free and bound measurements were combined for each sample, there were no significant differences in phenol or flavonoid concentrations between training systems for skin or seeds. In this study phenol and flavonoid concentrations did not conclusively correspond to light availability in the canopy.Additional index words: trellis, training system, wine grape, PAR, fruit quality
