Dylan Ellis, B. Robertson, C. Gillespie, M. Anderson, M.A. Walker, 
and Jean Dodson Peterson*  
*California Polytechnic State University, San Luis Obispo, One Grand Avenue, San Luis Obispo, CA 93407 (jdodsonp@calpoly.edu)

Cordon-trained, spur-pruned grapevines frequently exhibit non-uniform, developmentally delayed shoots at mid- and head-arm positions. The variation in vine growth, cluster development and ripeness impacts the timing and success of vineyard management activities such as leaf and cluster thinning and harvest. The objective of this research is to determine the role pruning severity and resulting shoots/meter have in minimizing developmental variation at the head-, mid- and end-shoot positions on a vine. The study was conducted in Oakville, California, on bilateral cordon-trained, spur-pruned Cabernet Sauvignon vines on 1.8 × 2.5 meter spacing. Vines were pruned to either 5.5 or 11.1 shoots/meter for a total of 12 or 24 buds per vine, respectively. Parameters tracked over the course of the season included shoot length, internode length and diameter, and pruning and cluster weights. In addition, berry chemistry analysis (soluble solids, pH, TA, and total phenolics) was performed at harvest. Shoots originating from arm positions at the end of cordons tended to be stronger sinks than those at mid and head positions. Specifically, fewer shoots/meter homogenized shoot internode length, diameter, and berry chemistry. The results of this study will be used to make pruning recommendations to address non-uniformity in vine growth and will serve to optimize vine balance and homogenize cluster production along the cordon arm.

Funding Support: California State University Agricultural Research Institute