Effect of fungicide pretreatment on lipid peroxidation, antioxidant enzyme systems and proline accumulation in tomato (Lycopersicon esculentum Mill.) leaves under high temperature stress

The aim of the present study was to determine the effect of high temperature stress (HT) and to evaluate the protective role of fungicide pretreatment against HT stress in tomato leaves. 'the oxidative stress was triggered under HT stress through an increase in the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2). Also, it caused a decline in photosynthetic pigments and enhanced the proline in tomato. However, the activities of catalase (CAT; EC 1.11.1.6), peroxidase (PDX; EC 1.11.1.7), and glutathione S-transferase (GST; EC.2.5.1.18), as well as ascorbate-glutathione cycle enzymes (APX, EC 1.11.1.11, DHAR, EC 1.8.5.1, MDHAR EC 1.6.5.4, GR; EC 1.6.4.2) were found to be increased after heat treatment. In addition, the transcript level of LeCAT1, LeAPX1, LeAPX6, LecGR, LeDHAR genes was up-regulated under HT stress. Foliar pretreatment of fungicide improved the physiological process that decrease H2O2 and MDA content, enhance pigment content, increase proline accumulation and CAT, PDX, and GST activity, as well as LeCAT1 and LeGST2 transcript levels compared to nonpretreated leaves under control temperature. When tomato leaves exposed to high temperature stress, fungicide pretreatment accelerated the antioxidant enzyme system by enhancing activities and gene expression levels of CAT, PDX, GST, and ascorbate-glutathione enzyme, resulting in the decrement of MDA and H2O2 contents. Further, the protective effect of fungicide pretreatment unproved the efficiency of the photosynthetic pigment under HT stress. Consequently, the study was to indicate the evidence for the ability of potential use of fungicide as a protective agent against HT stress in tomato