Soil salinity is one of the most agricultural problems that reduces the growth and yield of crops. Although, barley is the most salinity- tolerant plant among cereals but its seedling stage is the most sensitive developmental stage to salinity stress. Thereby to study the effect of salinity stress at seedling stage on biochemical traits including thiobarbituric acid reactive material (TBARM), catalase activity, and proline values, a factorial based on randomized complete design with four replications was conducted. The experimental factors included two levels of salinity (EC= 0 and 22 ds/m-1) and two barley genotypes (sensitive (Fajr) and tolerant (Afzal)). ANOVA results showed a significate effect for interaction between salinity and genotype (p<0.01) on all traits. Under salinity stress, thiobarbituric acid reactive material (TBARM), catalase activity, and proline values were increased in root and shoot of both genotypes at seedling stage. The higher value of proline and catalase activity, lower level of TBARM were observed in tolerant genotype (Afzal). Therefore, it seems that tolerant genotype copes with the oxidative and osmotic stresses induced by salinity through the increment of antioxidant activity and compatible solutes, respectively. Moreover, relative expression of three genes (NHX3, CAT1 and TIP2;3) in root and shoot were investigated under salinity stress at seedling stage. Expression pattern of NHX3, CAT1 and TIP2;3 genes in tolerant genotype under salinity stress revealed that they play roles in the salinity tolerance of barley. Thereby, aforementioned genes could be used as promising candidate genes for genetic tolerance to salinity stress in crops.

Keywords: Salinity, barley, biochemical traits, gene expression

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