Patterns of superoxide dismutase, catalase and peroxidase antioxidant isozymes in seedlings of white beans under salt stress

In this study the effect of salt stress on banding patterns of superoxide dismutase (SOD)، catalase (CAT) and peroxidase (POX) in 18 genotypes of white common bean (Phaseolus vulgaris L.) were examined under two levels of NaCl)0 and 400 mM) stress. For each isozymic band the “density × area” scores on gels were evaluated by MCID software and considered as enzymatic activity. Three isozymes were observed for SOD، one for CAT and three for POX. According to analysis of variance the difference between genotypes and between salinity levels were significant (P≤0. 001) for all isozymes except for POX2. The genotype by salinity interaction for SOD1، SOD2 and POX3 were significant (P≤0. 001). According to mean comparisons in common bean genotypes، SOD3 showed the most activity increment in first، third and fifth genotypes، CAT in eight، ninth and eighteenth genotypes، and POX1 in sixth، seventh and tenth genotypes. Genotype by salinity interaction analysis showed that the most increment activity of SOD1were observed in seventh، eighth، ninth، and twelfth genotypes، SOD2 in fourth، seventh، eighth، ninth، and thirteenth genotypes and POX3 in first، second and fourth genotypes under salt stress. Correlation estimates between antioxidant isozymes in normal، salt stressed condition and total (both normal and salt stressed conditions) showed only one positive and significant correlation between CAT and POX3 under salt stressed condition. Finally the results indicated that salt stress increased activities of all studied antioxidant enzymes.