Shijian Zhuang,* Qun Sun, Karl Lund, Matthew Fidelibus, and S. Kaan Kurtural
*University of California Cooperative Extension at Fresno, 550 E Shaw Ave Suite 210- B, Fresno, CA 93710 (gzhuang@ucanr.edu)

Cabernet Sauvignon is the second-most crushed variety in CA. The southern San Joaquin Valley is considered not ideal for growing premium Cabernet Sauvignon due to its arid, hot growing climate. However, the demand for high-quality Cabernet Sauvignon is strong and it has been a great interest for local growers and wineries to produce high-quality Cabernet Sauvignon at low cost to stay competitive. A two-way factorial split-plot design was implemented in a commercial vineyard located in Madera County in 2018, 2019, and 2020. Quadrilateral cordon-trained, spur-pruned Cabernet Sauvignon vines grafted onto Freedom rootstock were used under a sprawl system. Two levels of water deficits and three timings of mechanical leafing, replicated five times, were used in this study with six vines designated as an experimental unit. One water deficit was 80% ETc (targeted Ψ of -1.3 MPa) through the growing season with the other of 50% ETc (targeted Ψ of -1.5 MPa) from berryset to veraison and back to 80% ETc (targeted Ψ of -1.3 MPa) until harvest. The three timings of mechanical leafing were bloom, berry set, and no leafing. Midday leaf water potential (Ψ), fruit-zone photosynthetically active radiation (PAR), and leaf gas exchange were measured during the season. Water deficit significantly decreased yield through reduced cluster number and berry size without changing leaf area. Water deficit reduced TSS, titratable acidity, and 3-isobutyl-2-methoxypyrazine (IBMP) while improving berry anthocyanins. Leafing did not affect any yield component in our study but improved berry anthocyanins. Wine color was improved by water deficit and leafing.

Funding Support: American Vineyard Foundation