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

Ruby Cabernet is a cross between Cabernet Sauvignon and Carignan that was bred by Dr. Olmo to produce wine with more color and tannin in the arid, warm climate of the San Joaquin Valley. Local growers and wineries use this variety primarily as a blender to improve color and tannin structure of other premium red varieties like Cabernet Sauvignon or Merlot. High berry anthocyanins and tannin and high production per acre are desired for producing Ruby Cabernet. A randomized complete block design was implemented in a commercial vineyard located on the western side of Fresno County in 2018 and 2019. Quadrilateral cordon-trained, spur-pruned Ruby Cabernet vines grafted on Freedom rootstock were used under a sprawl system. Four timings of mechanical leafing, replicated five times, were used in this study, with five vines designated as an experimental unit. Water deficit was kept at 80% ETc (targeted Ψ of -1.2 MPa) from berry set to veraison and decreased to 60% ETc (targeted Ψ of -1.4 MPa) from veraison to harvest. Four timings of mechanical leafing included bloom, berry set, veraison, and no leafing. Midday leaf water potential (Ψ) and fruit-zone photosynthetically active radiation were measured during the season. Leafing reduced yield by 8% in 2018 and by 11% in 2019. Leafing had minimal effect on berry primary metabolites and leafing at bloom, and berry set improved berry anthocyanins by 16% in 2018 and 5% in 2019, with no benefit of leafing at veraison.

Funding Support: No external funding