Growth, Physio-Biochemical Aspects, Productivity and Fungicide Residue in Tomato Plants Affected by Tolclofos-Methyl (Rizolex) Fungicide and some Remediating Agents

Abstract

Vegetative growth of Tomato was negatively influenced by Tolclofos-methyl addition, and its phytotoxic effect was more pronounced on plant height and leaf area than other growth parameters. Application of Tolclofos-methyl fungicide at high rate caused marked decline in leaf chloroplast pigments, and carotenoids were more influenced. Total water content and leaf water deficit increased but the relative water content decreased as a result of Tolclofos-methyl application. Transpiration rate tended to increase at the lower dose of Tolclofos-methyl but decrease at its higher rate. Membrane integrity was increased with increasing the fungicide rate. Mineral elements (N, P, K, Ca, Mg, Fe, Zn, Mn), plant growth promoter substances (IAA, GA3, Cytokinins), and total free amino acids were reduced, whereas ABA, proline content, total phenol and the activity of phenoloxidase and peroxidase were increased in the fungicide exposed plants. Using Tolclofos-methyl fungicide at the high rate significantly reduced the number of flowers and fruit, vitamin C content of the fruits, yield, and water use efficiency of tomato plants. Total soluble solids and acidity in tomato fruits were increased, whereas lycopene content was decreased. Tolclofos-methyl fungicide residue in tomato fruits was dramatically enhanced above the maximum level of residue of Tolclofos-methyl fungicide (100 µg kg-1 in tomato fruits) and reached 176.8 and 423.2 µg kg-1 fresh weight at the rates of 2 and 4 g m-2 soil, respectively. Application of Bacillus, Trichoderma, GA3 and BP caused marked enhancements in the growth, yield, plant water relations, biochemical constituents, photosynthetic pigments and chemical properties of tomato fruits under both of the normal and fungicide pollution conditions. In addition, using these agents reduced the fungicide residue in fruits by about 42, 73, 35 and 5 % at the fungicide rate of 2 g m-2 soil and by about 80, 38, 68 and 47% at the rate of 4 g m-2 soil, respectively. It could be concluded that Trichoderma followed by Bacillus at the recommended dose of fungicide or Bacillus followed by GA3 at the exceeded dose of fungicide are useful tools to alleviate the phytotoxic effects and reduce the residue level of Tolclofos-methyl in tomato fruits below its maximum level.