A Comparative Study of Salt Tolerance of Three Almond Rootstocks: Contribution of Organic and Inorganic Solutes to Osmotic Adjustment

In this study, we assessed the relative contribution of organic and inorganic solutes to osmotic adjustment (OA) in three almond rootstocks subjected to four levels of soil salinity. The results showed that leaf water and osmotic potentials were affected by salinity in GF677 and Bitter almond, but less so in GN15, suggesting a higher selectivity for K+ and Ca2+ against Na+ in this latter rootstock. GN15 excluded Na+ and accumulated Cl-. Nevertheless, in this rootstock, Cl- and Na+ were the main osmolytes involved in OA, while the osmotic role of K+, Ca2+ and Mg2+ was small. Proline had the highest relative contribution of organic solutes to OA in the leaves of GN15 and GF677, while in Bitter almond it was not effective. The role of soluble sugars was rather marginal in terms of OA in all three genotypes. All three rootstocks displayed a degree of OA in the presence of high NaCl concentrations in the growth medium, but used different osmolytes to achieve it. Therefore, breeders should be careful in choosing biochemical parameters to assess OA capability of Prunus genotypes.