Journal of Crop Production and Processing

To examine the response of three rapeseed varieties to salinity stress, a pot experiment was conducted in a glasshouse using a factorial experiment based on a randomized complete block design with three replications. Three levels of NaCl (0, 100 and 200 mM NaCl) were imposed as the salinity treatments at root establishment (leaf 4) stage. In this study, sodium (Na⁺) and potassium (K⁺) concentrations and K⁺/Na⁺ ratio were compared in different tissues in three  varieties of rapeseed (PP-401-15E, Hyola401 and Hyola60) known to differ in salt tolerance, 30 days after salt treatment commencement. Effect of salinity was significant on all measured characters. The decline in shoot and root biomass and grain yield of salt sensitive genotype (PP-401-15E), were higher than those of the salt tolerants (Hyola401 and Hyola602) in response to salt stress. It seemed that the decrease in shoot biomass was primarily due to the osmotic effect of the salt, rather than the Na⁺-specific effects. The salt tolerant genotypes accumulated smaller quantities of Na⁺ in the shoot and root, indicating that the degree of salt tolerance in these genotypes depend upon the degree of salt exclusion from the plants. The salt sensitive genotype maintained a smaller K⁺/Na⁺ ratios in youngest fully expanded leaf than the salt tolerant genotypes. The ion partitioning capability in rape, thus, can considerably improve its salt tolerance. Relative membrane permeability was more notably increased in 200 mM NaCl in sensitive genotype (PP-401-15E) than the tolerant ones, and hence, can be used as selection criteria for improving salt tolerance.

An understanding of physiological mechanisms of salt tolerance is necessary for breeding programs, in order to select the desired trait in different wheat genotypes. Three bread wheat genotype differing in salt tolerance were employed to assess ion distribution and growth responses under saline conditions. To evaluate ion distribution in plant, sodium and potassium concentrations as well as K⁺/Na⁺ ratios in different tissues including root, leaf 3 blade, flag leaf sheath and flag leaf blade were assessed in a pot experiment in the glasshouse using a factorial experiment based on a randomized complete block design with three replications . Four levels of NaCl (0, 50, 100 and 150 mM NaCl) were imposed as the salinity treatments when the leaf 4 was fully expanded. Salinity had a similar effect on shoot biomass of all genotypes at 150 mM NaCl. Root biomass decreased in all genotypes with increasing salinity and this decrease was more in sensitive one (Tajan) at 150 mM NaCl. The genotypes did not differ significantly in root uptake of sodium. Sodium contents reduced from root to shoot and Salt tolerance in wheat genotypes was related to lower sodium accumulation in leaves. The major differences of salt tolerant genotypes (Arg and Mahdavi) and sensitive one in sodium transport to the younger leaf were due to the rate of transfer from the root to the shoot, which was much lower in Arg and the capacity of the leaf sheath to extract and sequester sodium as it entered the flag leaf blade in Mahdavi. Salt tolerant genotypes maintained higher K⁺/Na⁺ ratios in flag leaf blade than in salt sensitive one. Its likely that reduction in sodium transfer from the root to the shoot and leaf sheath sequestration specially in flag leaf are the traits that interact to control leaf blade sodium and would appear to be the most important mechanisms contributing to the improved salt tolerance in tolerant genotypes.