Selected rootstocks were evaluated for four seasons in a Zinfandel vineyard located in the northern San Joaquin Valley of California. The vineyard was drip-irrigated and vineyard spacing was 2.1m × 3.3m (vine × row). A two-wire vertical trellis system was used and row orientation was east to west. Vines were trained to a bilateral cordon and spur-pruned. Rootstocks included in the study were: AxR #1, Freedom, Harmony, Kober 5BB, and Teleki 5C. Vines grafted on AxR #1 rootstock were considered to be the control treatment.
A randomized complete block experimental design was used. There were six blocks and plots consisted of five vines. Data collected included yield, components of yield, fruit composition, bloom petiole nutrient content, shoot number, and pruning weight.
After the initial season, yields were consistently highest for vines grafted on Freedom rootstock, with yields only slightly lower on AxR #1 rootstock. Significantly lower yields were recorded for vines grafted on Kober 5BB and Teleki 5C. Rootstock did not have a consistent effect on fruit composition. Shoots/vine and shoots/meter of canopy were not significantly effected by rootstock. Dormant pruning weight was highest for Freedom and lowest for Kober 5BB.
These results suggest that rootstock selection can influence vineyard productivity in the northern San Joaquin Valley. Continued research is needed to determine long term effects of the rootstocks used in this study.