A Whole Plant Analysis of Chloride and Sodium Exclusion Using a Range of Grapevine Rootstock Genotypes

Background and Aims. Salt exclusion is an important attribute for wine grapes since many countries have limits to the concentration of sodium (Na⁺) and/or chloride (Cl⁻) tolerated in wine. The aim was to investigate whole plant capacity for Na⁺ and Cl‾ exclusion and the within-plant partitioning of accumulated ions to better understand these important salt tolerance traits. Methods and Results. Rooted cuttings of 140 Ruggeri and K51-40 (good and poor shoot Cl⁻ excluders, respectively) and five hybrids from a cross between the two genotypes were used. When challenged with salinity, 140 Ruggeri limited the accumulation of Cl⁻ and Na⁺ in the stem, petioles, and laminae and had a significantly lower whole plant concentration of Cl⁻ and Na⁺ when compared to K51-40. The latter indicates that 140 Ruggeri accumulates less Cl⁻ and Na⁺ than K51-40 by a lower uptake or a potentially greater efflux by roots, or both. While K51-40 accumulated significantly more Na⁺, it was able to retrieve it from the xylem; store it in the roots, stem, and petiole; and keep the lamina concentration comparable to that of 140 Ruggeri. Petioles of all genotypes appeared to play a role in limiting Cl⁻ accumulation in laminae and particularly for K51-40, to limit Na⁺ accumulation in laminae. Conclusions. The grapevine capacity for Cl⁻ and Na⁺ exclusion can be defined primarily as the lower net accumulation on a whole plant basis, reflecting the difference between the uptake and any efflux that may occur. Lower root to shoot transport is a key factor in shoot Cl⁻ and Na⁺ exclusion. Petiole accumulation assists in limiting the Cl⁻ and Na⁺ accumulation in the laminae. Significance of the Study. The study addressed the knowledge gap by examining Cl⁻ and Na⁺ exclusion on a whole plant basis, highlighting a range of within-plant mechanisms that act in limiting the accumulation of both ions in the laminae.