Biochemical examination of non-transgenic and transgenic soybean plants under drought stress conditions

Abstract

Drought is one of the major environmental stresses limiting crop production worldwide because both the duration and the severity of the stress are critical. Plants display a variety of physiological and biochemical stress responses towards prevailing drought stress thus making it a complex phenomenon. To address the modulation of stress responses, we used Glycine max cv. MG/BR 46 Conquista (non-transgenic) and cv. BRS Valiosa (transgenic) to analyze the effects of  progressive drought stress during two stages of soybean development (V2 and V4) on physiological and biochemical parameters. Three minimum soil water potentials (Ψs) were established: -0.03 MPa (well-watered), -0.07 MPa (a moderate stress), and -0.5 MPa (a severe stress). Gas-exchange measurements, lipid peroxidation, H2O2 and proline content, and antioxidant enzyme activities were analyzed in the leaves of both cultivars in the different water management levels. The results show a decrease in plant growth and gas-exchange parameters in both genotypes during progressive drought stress; the effects were more pronounced in MG/BR 46 Conquista. Proline content was less affected in BRS Valiosa. Malondialdehyde and H2O2 content increased during the drought stress but less in transgenic plants. Superoxide dismutase, catalase, and ascorbate peroxidase activities increased in BRS Valiosa at the V4 stage, whereas MG/B R 46 Conquista did not overcome stress conditions at this period. The overall results suggest that BRS Valiosa (transgenic) soybean cultivar exhibited later stress responses, which could enhance its survival during long periods of water deficit.