Applied Water and Rootstock Affect Productivity and Anthocyanin Composition of Zinfandel in Central California

A field study was conducted in central California to characterize the effects of rootstock genotype and amounts of applied water on the productivity and anthocyanin composition of Zinfandel (<i>Vitis vinifera</i> L.) grape berry in a hot climate. Zinfandel grafted onto either Freedom (Fresno 1613–59 × Dogridge 5, 27% <i>V. vinifera</i> hybrid; high vigor, nematode resistant) or Salt Creek (<i>V. champinii</i>; high vigor, phylloxera and nematode resistant, and salt tolerant) rootstock was studied during two growing seasons under sustained deficit irrigation (SDI) and regulated deficit irrigation (RDI). Midday leaf water potential (Y_l), canopy architecture, yield, berry composition, and berry skin anthocyanin concentration were measured at harvest. The Y_l of Zinfandel was consistently higher with SDI, while rootstock genotype did not affect it. Zinfandel grafted on Freedom consistently had greater berry weight, cluster number and weight, and yield per vine compared to Salt Creek. The seed number per berry and skin and seed mass of Zinfandel were greater when grafted on Freedom compared to Salt Creek. There were few effects of irrigation regimen or rootstock on berry composition in either year. Total berry skin anthocyanin concentration of Zinfandel was consistently greater with SDI than RDI and greater with Freedom in the second year. The tri-hydroxylated anthocyanin proportion of Zinfandel was consistently greater with Freedom rootstock. RDI reduced the water footprint of Zinfandel regardless of rootstock, but the associated decrease in yield was commercially unacceptable. Our results suggest that SDI in combination with Freedom rootstock can enhance water productivity based on limited reductions in yield combined with higher anthocyanin concentrations in berry skin in a resource-limited area.