Rootstock and salinity effects on rates of berry maturation, ion accumulation and colour development in Shiraz grapes

Shiraz grapevines on either their own roots, or on the rootstocks Ramsey, 1103 Paulsen, 140 Ruggeri or 101–14, were grown at two separate sites within the Murray‐Darling viticultural region with similar irrigation regimes but with an irrigation water salinity of either 0.43 dS/m (low salinity site) or 2.3 dS/m (high salinity site). Rootstock effects on grape berry development, ion concentrations, soluble solids and acidity were followed during one season. Wines were also made and compared using spectral analysis and sensory evaluation. Rootstock effects that were common across both sites were (1) a close relationship between K+and soluble solids accumulation in developing grape berries which commenced at the onset of veraison and was indicative of a link between K+and sucrose transport in the phloem, and (2), higher wine K+, pH and colour hue for all rootstocks with one exception, namely 101–14 at high salinity where 101–14 responded similarly to own roots. Juice K+, pH and loss of K+from juice during winemaking were highest for grapes from the high salinity site. Mean berry weight was smaller and the range in berry size across rootstocks was narrower at the saline site. The narrower range in berry sizes may have contributed to fewer rootstock effects on wine spectral characteristics at high salinity. There was no effect of rootstock on CO₂ assimilation rate or stomatal conductance at either site, although intrinsic leaf‐based water‐use efficiency measured as A/g was 50% higher at the saline site. All treatments exhibited berry shrivel at maturity, but the extent was smaller at high salinity. Slower development of berry colour during veraison was observed on some rootstocks, for example 101–14, and while unrelated to canopy size per se, a higher leaf‐to‐fruit ratio for 101–14 may have been a factor. Slower berry colour development during veraison had no bearing on the colour density of wine made from the harvested grapes.