Mitigation of adverse effects of chlorpyrifos by 24-epibrassinolide and analysis of stress markers in a rice variety Pusa Basmati-1.

The present paper first time reports the role of 24-epibrassinolide (EBL) in mitigating the adverse effects of Chlorpyrifos (CPF), a broad spectrum organophosphate insecticide by regulating the antioxidant defence system in an elite indica rice variety Pusa Basmati-1. It investigates the effect of CPF (0.02%, 0.04% and 0.06%) and EBL (10(-11), 10(-9) and 10(-7)M) treatments alone and in combination on rice seedlings. Various growth parameters, protein, proline and malondialdehyde (MDA) content and activities of antioxidant enzymes of seedlings were analysed. CPF showed an adverse effect on growth and protein content of seedlings whereas it leads to an enhancement in the level of MDA and proline content. The activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), guaiacol peroxidase (GPX) and monodehydroascorbate reductase (MDHAR) increased after treatment with CPF. Application of different concentrations of EBL along with CPF resulted in an overall improvement in the growth, level of protein and proline content and in the activity of various antioxidant enzymes whereas a decline in the levels of MDA content was observed. The work also investigated the changes at the transcript level of some key antioxidant enzymes like Cu/Zn-SOD, Fe-SOD, Mn-SOD, APX, CAT and GR. The expression of most of the genes was enhanced in response to CPF treatment. Application of EBL in conjunction with CPF resulted in a distinct enhancement in the transcript accumulation of Fe-SOD and CAT showing their important role in EBL mediated amelioration of CPF induced stress.