Salt-induced difference between Glycine cyrtoloba and G. max in anti-oxidative ability and K+ vs. Na+ selective accumulation

To characterize differences in soybean resistance to salt stress, two soybean species, the wild salt-tolerant soybean Glycine cyrtoloba (serial number ACC547) and the cultivated salt-sensitive soybean G. max (cv. Melrose) were treated with 0, 50, 100, or 150 mmol L− 1 NaCl for 5 days. A series of physiological parameters were determined in both shoots and roots, including content of chlorophyll (Chl) and malondialdehyde (MDA); electrolyte leakage (EL); hydrogen peroxide (H2O2) concentration; superoxide oxygen radical (O2−) production rate; activities of several enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD); and selective ion (Na+ and K+) accumulation. Our results showed that the relative salt tolerance of ACC547 was associated with lower loss of Chl content; lower MDA content, EL, H2O2 concentration, and O2− production rate in both shoots and roots; higher POD activity caused by new isoforms in roots; and higher K+ concentration and K+/Na+ ratio in shoots. These results suggested that relative lower membrane injury, efficient K+ vs. Na+ selective accumulation, and newly induced POD isoenzymes are mechanisms of salt tolerance in soybean.