Abstract
Moderate levels of Cl- have been associated with grapevine salt tolerance. The hypothesis to be tested in this work is: photosynthesis in grapevine is negatively correlated with foliar Cl- concentration. To further test this hypothesis, multiple mild salinity experiments on four different Vitis genotypes (Cabernet-Sauvignon, Riparia Gloire, Ramsey and SC2) were conducted and photosynthesis, ion concentrations and gene expression responses were quantified. The salt-tolerant rootstock Ramsey had greater Cl- exclusion capabilities than V. vinifera cultivars both during rooted cutting greenhouse experiments and three years of field-grafted experiments; SC2 also excluded Cl-. Differential gene expression indicated that salinity affected transcript abundance more in salt-sensitive genotypes (97.7 % of DEGs in the dataset), especially chloroplast-related transcripts. The transcript abundances of known anion transporters were determined and a family of putative B transporters was associated with the Cl- exclusion phenotype. Photosynthesis and growth were maintained in Ramsey and SC2 under mild salinity. However, photosynthesis declined in Cabernet-Sauvignon with isosmotic 20 mM salt concentrations of NaCl, KCl or NaNO3, independent of the salt type. While foliar Cl- concentrations did correlate with salt tolerance during control and NaCl conditions, it was not found to be the cause of photosynthetic decline in Vitis during mild salinity.
Highlights
Salinity is a prevalent abiotic stress affecting agricultural land throughout the world (Rengasamy, 2006)
Salt sensitivity was associated with elevated shoot Cl-The small pot salinity experiments were conducted in the greenhouse to test the hypothesis that: RA and SC are salt-tolerant and will maintain growth while reducing shoot Cl- accumulation relative to the salt-sensitive CS during mild salinity
One and two-week mild salinity (20 mM NaCl) experiments were performed with plant growth measurements, transcriptomic expression analysis and shoot Cl- quantified after the experiments
Summary
Salinity is a prevalent abiotic stress affecting agricultural land throughout the world (Rengasamy, 2006). The USDA defines salinity as soils with an electrical conductivity (EC) above 4 dS m-1, an exchangeable Na+ percentage below 15 and a soil pH below 8.5 (Allison et al, 1954). While ions such as Mg2+, Ca2+, K+, SO42- and HCO3- are known to contribute to salinity, the majority of research into the subject has involved Na+ and Cl-. This is because they are two of the most soluble and widespread salts, and because many crops are sensitive to these ions (Munns and Tester, 2008)
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