Exogenous Salicylic Acid-Mediated Physiological Responses and Improvement in Yield by Modulating Antioxidant Defense System of Wheat under Salinity

Abstract

Present study investigates the regulatory roles of exogenous salicylic acid (SA) in physiology, antioxidant defense systems and yield of wheat under different salt stress condition. The experiment was conducted with two varieties i.e. BARIGom 21 and BARIGom 25 and ten salt stress treatments viz. control (without salt), SA (1 mMsalicylic acid), S50 (50 mMsalt stress), S50+SA (50 mMsalt stress with 1 mMSA), S100 (100 mMsalt stress), S100+SA (100 mMsalt stress with 1 mMSA), S150 (150 mMsalt stress), S150+SA (150 mMsalt stress with 1 mMSA), S200 (200 mMsalt stress) and S200+SA (200 mMsalt stress with 1 mMSA). Leaf relative water content (RWC) and chlorophyll (chl) content reduced due to salt stress. The malondialdelyde (MDA) and H2O2 were increased under the stress condition. The ascorbate (AsA) content, reduced glutathione (GSH) and GSH/GSSG ratio were reduced by salt stresses (50, 100, 150 and 200 mM, respectively). But the glutathione disulfide (GSSG) amount increased with an increase in the all level of salinity. The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase (CAT) activities showed a significant reduction in response to salt stress but CAT increased only at 100 mM stress condition. The glutathione S-transferase (GST) and glutathione reductase (GR) activity increased significantly with severe salt stress (200 mM). But the activity of peroxidase (POD) was decreased with increasing salinity level. At harvest, salt stresses reduced the effective tiller hill-1, 1000 grain weight, grain yield, straw yield, biological yield and harvest index for both of varieties. However, number of non-effective tiller hill-1 significantly increased in response of salt stress. Exogenous 1 mM SA application with salt stress improved physiological parameters, yield and reduced oxidative damage in both cultivars whereBARI Gom 25 showed better tolerance. But, SA application could not improve physiological parameters and yield at extreme level of salt stress (200 mM).