Differential Response of Salt-Tolerant and Susceptible Barley Genotypes to Salinity Stress

The performance of selected salt-tolerant genotypes of barley [Hordeum vulgare (L.)], derived using field and greenhouse assessment methods, was evaluated under greenhouse and field conditions. Two barley genotypes, one salt-tolerant and one salt-sensitive, selected from each of the methods, were used. This study was conducted under both saline and non-saline field conditions, as well as under greenhouse conditions with salinized solution culture at 0 mM (control), 100, 200, 300, and 400 mM NaCl. Days to heading, days to maturity, plant height, number of grains per spike, grain weight per spike, 1000 grain weight, number of spikes per square meter, grain yield, harvest index and some physiological characters were measured. Plant dry weight and accumulated Na+, K+, and Ca2+ were measured 20 days after salinity treatments. The field salinity significantly reduced (P < 0.01) the means of all traits averaged on two tested genotypes. Under greenhouse conditions, the salt-tolerant genotype 'Afzal' produced the highest dry weight and K+/Na+ ratio under salt-stress conditions (200 mM). The influence of NaCl on parameters including protein and chlorophyll concentrations and membrane permeability was investigated in young and old leaves of cultivars, differing in salt resistance. NaCl-induced senescence also involved specific modifications, such as a transient increase in soluble protein concentration recorded in salt-resistant genotypes only. Alteration of membrane permeability appeared as one of the first symptoms of senescence in barley leaves and allowed discrimination among cultivars after only the seventh day of stress. Since a higher tolerance to salinity in Afzal was apparently associated with a lower concentration of Na+ and a higher K+/Na+ ratio of the shoots, this trait could probably be used for yield improvement of barley cultivars under saline conditions. It is can concluded from our findings that a relationship exists between genotype-specific salinity tolerance and the accumulation of proline in the leaves and roots along with higher uptake of sodium and chloride, lower decrease in the water and osmotic potential, less inhibition in the yield under salinity stress.