Comparative Analysis of the Reaction to Salinity of Different Chickpea (Cicer aretinum L.) Genotypes: A Biochemical, Enzymatic and Transcriptional Study

Oxidative stress is one of the serious biochemical consequences of environmental stresses, particularly salinity. The present study was conducted to evaluate biochemical, antioxidative enzymes and the corresponding gene expression responses of four contrastive chickpea genotypes to 100 mM NaCl stress during 12 days. The salinity stress imposed significant increases (p ≤ 0.05) compatible osmolytes, that is, proline and soluble carbohydrate, especially in the most tolerant genotype (T1) by 14.87 µmol g−1 DW and 204 mg g−1 DW after 12 days of stress, respectively, to assist in osmotic adjustment and maintain cell membrane integrity to preserve cell turgor. Similarly, 7 days of salinity incurred differential increases in enzymatic activities of T1 and the most sensitive genotype (S2) by 66 and 20% for SOD, 138 and 15% for CAT, 179 and 77% for APX, and 172 and 136% for GR over the relative controls, respectively. Furthermore, corresponding transcript profiles for some predominant isoforms of enzymes were analyzed using the RT-PCR technique. Results revealed the same genotype-dependent changes, correlating well with higher activity of SOD, CAT, APX in T1 (0.97***, 0.80**, and 0.86**) as compared with S2 (0.91***, 0.58ns, and 0.84**). The data showed that higher activities of antioxidant enzymes as well as earlier and more up-regulation of their corresponding gene expressions in T1 could be some reasons for salinity tolerance in this genotype to cope with oxidative stress. This reaction was also accompanied by lower chlorophyll degradation (−37%), the lowest MDA formation (224%), and higher RWC (−31%) in T1 relative to respective control.