Evaluation of Canopy Division and Cane Pruning to Retrofit Spur-Pruned, Vertical Shoot-Positioned Petit Manseng

Summary Goals: Single canopy training with vertical shoot positioning is the predominant training and shoot positioning system in Vitis vinifera vineyards. We questioned if a single canopy with vertical shoot positioning was the most productive system on which to cultivate the modest-yielding cultivar Petit Manseng. We retrofitted low, bilateral cordon-trained, spur-pruned Petit Manseng vines trained to a single canopy by dividing the canopy and implementing bilateral or quadrilateral cane pruning (QCP). Our goals were to evaluate the effects of three different pruning techniques in combination with two training techniques on canopy architecture, crop yield, and primary fruit composition over two years. Key findings: Spur pruning increased pruning weight by 0.1 kg/m row compared to QCP. Divided, vertical shoot positioning increased pruning weight by 0.1 kg/m row compared to single canopy, vertical shoot positioning. A 101% greater leaf exposure layer and 56% greater leaf layer number were observed in midcanopies of single canopy, vertical shoot-positioned plots relative to divided, vertical shoot-positioned plots. QCP increased crop yield by 44% (2017) and 34% (2018) when compared to the average of bilateral cane pruning and spur pruning. QCP combined with divided, vertical shoot positioning increased crop yield by 79% when compared to spur pruning combined with single canopy, vertical shoot positioning in 2018. QCP produced an average crop load of 12.4, 126% greater than that produced by spur pruning over two seasons; while divided, vertical shoot positioning produced an average crop load of 7.2, 33% lower than that produced by single canopy, vertical shoot positioning. Impact and significance: Spur pruning produced a lower crop load than QCP. The relatively high crop load in QCP indicated overcropping. That unbalanced source:sink relationship was alleviated through the use of canopy division, which decreased canopy self-shading and increased crop yield when compared to single canopy, vertical shoot-positioned training in the second of two years. “Athena” is a novel training system that combines a divided, vertical shoot-positioned canopy with QCP to improve exposed canopy leaf area and crop production, respectively. While similar to a Lyre system, which generally employs cordon training and spur pruning, Athena employs cane pruning and is a retrofit option in vineyards trained to single canopies. The Athena system does require further testing over an extended time period, in various growing conditions and in several cultivars, and it is already being tested by southeastern U.S. growers.