Impact of Training System and Pruning Severity on Yield, Fruit Composition, and Vegetative Growth of ‘Niagara’ Grapevines in Michigan

‘Niagara’ (Vitis labruscana Bailey) vines were evaluated for 4 years, from 2000 to 2003 in a commercial vineyard in Scottdale, MI. Vines were trained as Hudson River Umbrella (HRU), umbrella Kniffen (UK), and Hybrid (HYB) and pruned for 4 years at four pruning levels (20, 40, 80, or 120 nodes/vine) and minimally pruned or hedge pruned mechanically. Node levels above 80 nodes decreased several yield components, such as cluster and berry weight. Reduction in yield and sugar components was obtained with pruning levels above 80 nodes per vine and related to a decrease in cluster and berry weight as well as a decrease in bud fruitfulness (productivity index). As number of nodes retained increased, vine size, cluster weight, berry weight, percent soluble solids, and pH decreased, while yield, cluster number, and leaf area at veraison increased. Yield components, vine size, and productivity were optimum at 20 and 40 nodes retained, but these node levels produce unacceptable low yields for economically viable juice grape production in Michigan. Therefore, retaining 80 fixed nodes produced sustainable production, without compromising vine health or long-term vineyard sustainability. There were no differences between HRU, UK, and HYB on vegetative or reproductive parameters or on fruit composition. Thus, the choice of training system—HRU, UK, or HYB—should be based on specific grower and vineyard needs.