Drought stress-induced antioxidative defense responses were studied in seven soybean (Glycine max (L) Merr.) cultivars PUSA 9712, LSB 1, JS 335, ADB 22, NRC 37, DSB 20, and MAUS 61, respectively. Drought stress was imposed by withholding irrigation till the leaf water potentials reached -1.0, -1.5, and -2.0 MPa. Lipid peroxidation and superoxide, H2 O2 , • OH, DPPH radical scavenging assays were performed. Antioxidants during drought stress were studied by quantifying the ascorbic acid, glutathione, α-tocopherol, phenolics, flavonoids, tannins, enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase. Antioxidant levels were significantly high in soybean foliages exposed to drought with the increased concentrations of radicals and enhanced lipid peroxidation rates. Isoenzyme analysis of SOD has shown the upregulation of Cu/Zn and MnSODs. Our results demonstrate that cultivars PUSA 9712 and LSB1 have shown to possess a high rate of antioxidants and a very efficient antioxidative defense system when compared with other cultivars. PRACTICAL APPLICATIONS: Soybean (Glycine max (L.) Merr.) is an economically important cash crop, cultivated globally for its rich protein, oil, nutraceutical, and antioxidant constituents. It is also cultivated for its rich enriched food, animal feed as well as several other commercial products. In India, most of the soybean cultivation is being done under rainfed conditions. Hence, identification of superior soybean cultivars rich in antioxidants is very important. The work presented here is the output of the investigation carried out on cramming the changes in antioxidative defense mechanisms of seven popular soybean cultivars that are regularly cultivated in India. A study was performed by quantifying the radicals, H2 O2 concentrations, lipid peroxidation, determination of enzymatic, and nonenzymatic antioxidants in all selected soybean cultivars exposed to control and increased the duration of drought stress, for the identification of superior cultivars with a rich avenue of enzymatic and nonenzymatic antioxidants.
Keywords: ROS; antioxidants; drought stress; secondary metabolites; soybean cultivars.
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