Reduced irrigation and rootstock effects on vegetative growth, yield and its components, and leaf physiological responses of Shiraz

Abstract

Background and Aims: The study investigated whether rootstocks can modify grapevine responses to reduced irrigation. Methods and Results: Drip-irrigated Shiraz vines on eight rootstocks were subjected to industry standard and 30% reduced irrigation regimes over four seasons. Reducing irrigation decreased pruning weights and yield, but did not consistently affect irrigation water use index (IWUI). It increased leaf Δ13C. Reduced irrigation and elevated vapour pressure deficit (VPD) were associated with decreases in leaf water potential (ψl), leaf stomatal conductance and assimilation rate. Reducing irrigation raised leaf transpiration efficiency, whereas elevated VPD lowered it. These effects of reduced irrigation were independent of rootstock. Vines grafted to 101-14 had a higher ψl and achieved the highest yield and IWUI. The yields of vines grafted to Ramsey, Schwarzmann and 140 Ruggeri were also high. Vines grafted to 101-14, Ramsey and 1103 Paulsen had the higher rates of leaf assimilation. Rootstock did not affect Δ13C. Conclusion: The gain in leaf transpiration efficiency caused by reducing irrigation was not associated with a gain in IWUI. Rootstocks 101-14, Ramsey, Schwarzmann and 140 Ruggeri achieved higher yields and IWUI under both standard and reduced irrigation regimes. Significance of the Study: Among grafted vines growing on saline soil but receiving non-saline irrigation water and subject to a 30% reduction in irrigation, the yield responses of vines grafted on rootstocks rated as having good drought tolerance were the same as those of vines grafted on rootstocks rated as having poor drought tolerance.