AbstractsBiology & Animal Science

Vertically shoot positioned (VSP) training systems are common in Oregon's Willamette Valley, where deep fertile soils and high regional precipitation task growers with curbing vegetative vigor within this system. Management strategies, such as canopy hedging and cluster-zone leaf removal, are used to improve microclimate within the canopy and around the fruit. These cultural practices employed in commercial vineyards make it difficult to quantify canopy architecture and vine growth using currently established methods. Given the importance of vine leaf surface area to productivity of the vine, a study was conducted to determine how to best quantify leaf area in the highly managed VSP canopies. A regression model was developed from various linear leaf measures compared to leaf area measures on primary and lateral leaves of Pinot noir vines in the north Willamette Valley of Oregon. Maximum leaf length, maximum leaf width, mid-vein length and the distance between the central and interior lateral lobe tips were positively associated with total leaf area. Leaf width at the petiole junction was not a suitable measure. A second study was conducted to evaluate methods for quantifying vine leaf area and leaf distribution in moderate and high vigor VSP canopies, where dense foliage and interlacing shoots and tendrils can make vine measurements difficult. Traditional point quadrat analysis, digital photography, and a template leaf area method were compared to leaf areas determined by destructive sampling. Results show that point quadrat analysis severely overestimated the number of shaded canopy leaves in dense VSP systems. Results from the digital photography pixel recognition program correlated green pixels with leaf exposure but was not in good agreement with exterior canopy leaf area. The template leaf area method results confirm that it can accurately estimate total vine leaf area. The third study was developed to integrate these canopy quantification techniques with understanding how the leaf area: yield relationship affects fruit composition at harvest in cool climate Pinot noir grapes. A range of leaf area to yield ratios was created by cluster thinning vines to two crop levels. The study was replicated across four commercial vineyards with varying levels of moderate and high vigor. Results indicate that crop thinning had no impact on canopy leaf area, and there was limited impact of yield on fruit composition over two seasons. The studies included herein aimed to develop and evaluate methods for estimating leaf area within VSP-trained canopies in the Willamette Valley. Results of this work will provide improved methods by which viticulture researchers and whole-plant physiologists can employ to determine leaf area as a measure of vine productivity, and better understanding of source-sink relationships in managed canopies.