Precipitation before bud break and irrigation affect the response of grapevine ‘Zinfandel’ yields and berry skin phenolic composition to training systems

Abstract

A 3-year trial was conducted in the hot climate of central California to assess the effect of training systems, irrigation treatments and their integration on canopy architecture, yield and flavonoid composition of ‘Zinfandel’grapevine. Training systems were spur-pruned (SP, 22 two-node spurs; 44 buds), split-canopy cane-pruned (CP, six-canes with 8-nodes; 48 buds), and mechanically-pruned (MP, 100mm hedge; 116 buds). Irrigation treatments were; sustained deficit irrigation (SDI), receiving 80% of crop evapotranspiration (ETc) from bud-break to leaf fall; and regulated deficit irrigation (RDI) receiving 80%, 50%, and 80% of ETc between bud-break and fruit set, fruit set to veraison and veraison to leaf fall, respectively. The vineyard received 87%, 30% and 23% of the ten-year average of winter precipitation in years 2013, 2014 and 2015, respectively. In year 2013, combination of CP and RDI performed better based on yields and grape skin flavan-3-ols, flavonols and total tannin concentration. However, CP under SDI treatment yielded the greatest total anthocyanin concentration in 2013. In 2014 and 2015, combination of MP and SDI had the greatest yield and anthocyanin concentration whereas MP under RDI tended to produce higher concentration of flavan-3-ol monomers, total flavonols and total tannins. Yields and grape composition were improved by high water availability. In lower precipitation years, yields and grape composition were ameliorated by MP. The regulated deficit irrigation treatment did not consistently improve grape composition in an arid region. The study provides information to identify combinations of training systems and irrigation treatments that can optimize reproductive and vegetative development while maintaining commercially acceptable flavonol, flavan-3-ol monomers and anthocyanin concentration in berry skin in a hot and arid climate.