Amelioration of the adverse effects of thiram by 24- epibrassinolide in tomato (Solanum lycopersicum Mill.)

Abstract

This study investigated thiram fungicide-induced-stress effects in tomato plants and the possible protective role of 24-epibrassinolide (24-EBL) in response to thiram (tetramethyl thiuram disulfide) toxicity. Tomato seedlings pretreated with 0, 10-11, 10-9 and 10-7 M 24-EBL were treated with 6.6 mM thiram. Tomato leaves harvested 5 and 11 days after thiram treatment (DAT) were used for analysis. Thiram application caused oxidative stress by increased hydrogen peroxide and malondialdehyde levels, whereas the chlorophyll a, b and carotenoid amounts and total protein content decreased. In addition, the activities of antioxidant enzymes such as catalase, ascorbate peroxidase and glutathione reductase decreased in the thiram-treated tomato plants on DAT 5 and 11 while pesticide detoxification enzymes (peroxidase and glutathione- S-transferase) activities increased. The thiram-induced oxidative stress was alleviated after pretreatments with different concentrations of 24-EBL. The hydrogen peroxide and malondialdehyde levels decreased and the amounts of photosynthetic pigments and total protein content increased after 24-EBL pretreatments. In addition, the activities of antioxidant enzymes and pesticide detoxification enzymes further increased as the concentration of 24-EBL decreased in tomato under thiram stress, and the most effective concentration was determined as 10-11 M 24-EBL. The results suggested that 24-EBL could effectively alleviate thiram-induced phytotoxicity in tomato plants.