Tian Tian* and Matthew Fidelibus
*University of California Cooperative Extension, Kern County, 1301 South Mount Vernon Ave, Bakersfield, CA, 93307 (titian@ucanr.edu)

Although numerous trials have evaluated the influences of rootstocks on vine growth and berry composition in different production regions, rootstock effects on mature vines remain less known. GRN rootstocks are rarely compared with traditional rootstocks in mature vineyards. To understand the long-term effects of newer and traditional rootstocks on vine productivity and fruit quality, we obtained data in 2021 and 2022 from an older ‘Autumn King’ vineyard in Ducor, CA. The vineyard was planted in 2008 in loam soil. Own-rooted vines and vines on 12 rootstocks (Freedom, Harmony, Teleki 5C, Salt Creek, 1103 Paulsen, Crimson, 10-17A, RS-3, GRN-1, GRN-2, GRN-3, and GRN-4) were evaluated. Each rootstock was replicated five times with five vines each. Rootstocks had similar effects on vine productivity across two years. Vines on Salt Creek, GRN-2, GRN-3, Teleki 5C, and 1103 Paulsen performed well, showing higher yields and larger canopies than others. Vines on Freedom, RS-3, Harmony, and GRN-4 had intermediate yield and canopy growth. Vines on 10-17A had moderate yield, but a large canopy, suggesting vines on this stock may favor vegetative growth more than other stocks. Vines on GRN-1 performed poorly and had similar yield and growth as own-rooted vines. Because of limited canopy growth, the fruit of vines on GRN-1 and own-rooted vines was overly exposed, resulting in sunburn and fruit yellowing in both years. Vines on Crimson had intermediate yield and pruning mass in 2021, but their productivity declined in 2022. Rootstocks had minor influences on bud fruitfulness, vine water status, and berry composition (total soluble solids, pH, titratable acids, and berry firmness) at harvest. Overall, we found that GRN-2 and GRN-3 can be alternatives to popular traditional stocks, including Freedom, Salt Creek, and 1103 Paulsen, in areas with similar climate and soil conditions as the San Joaquin Valley of California.

Funding Support: American Vineyard Foundation and UC ANR