Larry Bettiga* 
*University of California Cooperative Extension, 1432 Abbott Street,
Salinas, CA 93901 (lbettiga@ucdavis.edu)

Twelve rootstocks were evaluated for three years (2014 to 2016) in a Chardonnay vineyard near Soledad in the Salinas Valley of California. The site was previously planted with vines that were infested with phylloxera and root knot and ring nematodes and was not fumigated prior to replanting. The soil is a Chualar loam with an approximate rooting depth of 1 m. Vines were head-trained and cane-pruned to two canes and two spurs on a vertically shoot-positioned trellis. Vine spacing was 1.5 × 1.9 m (vine × row). The experimental design was a randomized complete block with eight replications of the 12 rootstocks using five vine plots. GRN1, GRN2, GRN3, GRN4, and GRN5 were compared to RS3, RS9, 1103P, 101-14M, SO4, O39-16, and St. George. Data collected included yield, components of yield, fruit composition, and growth components. Crop yield was signifi-cantly influenced by rootstock and the three-year averages ranged from 5.10 to 7.91 kg/vine. Yield separated into three groups, with St. George and 1103P being higher, and O39-16 and GRN1 lower. Higher cluster number was the factor most influencing crop yield. Higher-yielding rootstock selections also had higher cluster weight due to more berries per cluster. Pruning weights ranged from 0.34 to 0.85 kg/vine, with 1103P and St. George having the largest weights and O39-16 and GRN1, the smallest. Fruit composition was significantly affected by rootstock due to crop load and canopy differences.

Funding Support: No external funding