TY - JOUR T1 - The Effect of Postharvest Defoliation on Carbon and Nitrogen Resources of High Yielding Sauvignon blanc Grapevines JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic DO - 10.5344/ajev.2016.15081 SP - ajev.2016.15081 AU - M.M. Greven AU - S.M. Neal AU - D.S. Tustin AU - H. Boldingh AU - J. Bennett AU - M.C. Vasconcelos Y1 - 2016/04/07 UR - http://www.ajevonline.org/content/early/2016/04/05/ajev.2016.15081.abstract N2 - We quantified the importance of post-harvest carbohydrate assimilation and nitrogen availability to replenish vine reserves, additional to maintaining optimal growth, productivity and fruit quality of high yielding vigorous Sauvignon blanc grapevines. To create different carbohydrate (CHO) and nitrogen (N) reserve concentrations, our factorial-design trial consisted of a post-harvest defoliation treatment overlaid with a pruning treatment for which 48 and 72 nodes were retained on, respectively, four- and six-cane vertical shoot positioned (VSP) vines. For defoliation (Defol), immediately after fruit harvest, all the leaves of the vines were removed, compared to foliated vines (Fol) that went through normal senescence. From just after ecto-dormancy in 2008, samples of root and trunk tissue were taken throughout the years for CHO and N analyses, and results compared with annual yield data. In the seasons following the treatments, both the defoliation and node number treatments reduced vine growth and yield. Additionally, differences in CHO and N of the permanent structure were found. Depleted winter reserves in trunk and root were replenished during the next growth cycle, suggesting that grapevine N and CHO partitioning favor survival of the permanent structure over increasing vine size and yield. However, after two consecutive years of defoliation, the cumulative effects of smaller, less fruitful canes from year 1 and reduced carbohydrates from the subsequent year, did reduce both yield and vegetative growth in the third growing season. Therefore, even the short-lived post-harvest canopy in cool climates contributes to the vine CHO economy. Defoliation or excessive crop loads affected carbohydrate reserves in vines but only after a few consecutive years of low recharge was this manifested in lower yields and poorer vegetative growth. ER -