EFFECT OF FRUIT ZONE LEAF REMOVAL ON TOTAL GLYCOCONJUGATES AND CONJUGATE FRACTION CONCENTRATION OF RIESLING AND CHARDONNAY (VITIS-VINIFERA L.) GRAPES

Grape glycosides are, in part, important aroma and flavor precursors. Their quantification may offer a means of determining the impact of vi ticultural practices, such as leaf removal, on potential wine quality. Fruit zone leaf removal of Riesling and Chardonnay grapevines grown a t two sites for two seasons was evaluated for its influence on total a nd phenol-free grape glycosides at harvest. Vines were trained to a lo w bilateral cordon system at one vineyard and a high bilateral cordon at the other. The concentrations of total and phenol-free glycosides w ere higher in Riesling and Chardonnay fruit from leaf-pulled vs contro l vines at three of four harvest dates. Phenol-free glycosides average d 80% of the total in Riesling juice and 66% of the total in Chardonna y. Grapevine canopy microclimate plays an important role in determinin g fruit composition, although knowledge about the relationship between microclimate and aroma/flavor development is limited. This study illu strates the affect of microclimate manipulation on grape glycosides, i mportant components of fruit quality.