Rootstock effects on salt tolerance of irrigated field-grown grapevines (Vitis vinifera L. cv. Sultana).: 1. Yield and vigour inter-relationships

Vegetative growth and yield of grapevines grown in the field on their own roots or grafted to a range of rootstocks were investigated under drip irrigation with water of three salinity levels (0.40, 1.75 and 3.50 dS/m) over a five‐year period. Rootstocks were Ramsey, 1103 Paulsen, J17–69 and 4 hybrids (designated R1, R2, R3 and R4) derived from parentage involving Vitis champini, V. berlandieri and V. vinifera. Of measured yield components (bunches per shoot, bunches per vine, weight per bunch, weight per berry and total yield), only weight per berry was significantly reduced by high salinity (3.50 dS/m) in each year of the trial with the exception of Sultana on 1103 Paulsen and R2 in 1991 and Sultana on Ramsey in 1993. Weights of one‐year‐old pruning wood were also reduced by high salinity in all years for own roots and all rootstocks, with the exception of R2. Mean yield values at each salinity level over the five‐year period of the trial were highest for Sultana on Ramsey, 1103 Paulsen and R2. High salinity had no effect on five‐year mean yields of Sultana on Ramsey, 1103 Paulsen and R2. Yield (five‐year means) of Sultana on Ramsey and R2 at 1.75 dS/m were significantly higher than at 0.40 dS/m by 14.6% and 13.4% respectively. In contrast, 5‐year mean yields of Sultana on J17–69, own roots, R1, R3 and R4 at 3.50 dS/m were reduced by 54, 30, 20, 30 and 30% respectively. Yield of Sultana on J17–69, R1 and R4 rootstocks was reduced by 47, 20 and 24% respectively at 1.75 dS/m. When yield was regressed against bunches per vine and weight per bunch for Sultana on own roots and on Ramsey rootstock, bunches per vine was the main determinant of yield, while weight per berry showed a poor correlation with yield at all salinity levels. Rootstock ranking for salt tolerance based on yield at high salinity was the same as rankings for pruning wood weights at high salinity. The same occurred at medium salinity, demonstrating that vigour imparted by the rootstock was a major factor in Sultana salt tolerance as measured by yield. Mean root weighted soil saturation paste electrical conductivities (RWEC_e) (determined from soil saturation paste salinities and root length densities) were in the range 2.0–2.6 dS/m for the low salinity treatment, increasing to approximately 5.4 dS/m with increasing salinity of irrigation water. Yield reduction for own‐rooted vines for each 1.0 dS/m increase in RWEC_e above 2.6 dS/m was 9.3%.