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Tradescantia-Micronucleus (Trad-MCN) test on the genotoxicity of malathion
Abstract:
The Tradescantia-Micronucleus (Trad-MCN) bioassay was utilized to determine the genotoxicity of Malathion, a common insecticide. Four different treatment procedures were applied: a) absorption of Malathion/water mixture (with or without DMSO and/or S-9) through the stem, b) spraying a Malathion/water mixture onto the plant cuttings in enclosed chambers, c) spraying a Malathion/water mixture on an open population of plants in the greenhouse, and d) absorption of Malathion fumes through the leaves and buds. Most treatments were administered for 6 hr, followed by a 24-hr recovery time. Slides were prepared from the samples and scored for micronucleus (MCN) frequencies. Results of 16 experiments indicated that the genotoxicity of liquid Malathion absorbed through the stem was very low and often masked by high toxicity, causing dead cells in the stem, leaves, and meiocytes. Malathion spray at the dosage of 0.435% in an enclosed chamber or on an open population of plants yielded negative responses. Malathion fumes at dosages of 0.15-0.25% induced significantly higher (0.05) MCN frequencies above the controls and altered the nuclear structure to form unequal sized nuclei and multiple breaks in each of the four cells of a tetrads. It also caused degeneration of nuclei, "protrusions on nuclei," and inhibition of cell growth. Higher dosages (above 0.25%) were toxic.
Insights
Malathion fumes, but not liquid or sprayed forms, showed genotoxicity in Tradescantia plants. Malathion fumes induced micronuclei and nuclear damage, indicating potential risks from inhalation exposure.
Area of Science:
- Environmental toxicology
- Plant science
- Genetics
Background:
- Malathion is a widely used organophosphate insecticide.
- Assessing insecticide genotoxicity is crucial for environmental and health risk evaluation.
- The Tradescantia-Micronucleus (Trad-MCN) assay is a sensitive method for detecting genotoxicity in plants.
Purpose of the Study:
- To evaluate the genotoxicity of Malathion using the Tradescantia-Micronucleus (Trad-MCN) bioassay.
- To compare the genotoxic effects of Malathion under different exposure routes and conditions.
Main Methods:
- Four exposure methods were used: stem absorption, spraying in chambers, open-air spraying, and fume absorption.
- Tradescantia plants were exposed to Malathion for 6 hours, followed by a 24-hour recovery period.
- Micronucleus (MCN) frequencies and nuclear abnormalities were analyzed in plant cells.
Main Results:
- Liquid Malathion absorbed via stem showed low genotoxicity, often masked by high toxicity and cell death.
- Spraying Malathion (0.435%) did not induce genotoxic effects in enclosed or open plant populations.
- Malathion fumes (0.15-0.25%) significantly increased MCN frequencies, altered nuclear structure, and caused cell damage.
Conclusions:
- Inhalation exposure to Malathion fumes presents a genotoxic risk to plants, inducing significant DNA damage.
- Liquid and sprayed Malathion formulations have limited genotoxic potential via stem absorption or foliar application under tested conditions.
- The Trad-MCN assay effectively identified genotoxic effects of Malathion fumes, highlighting the importance of exposure route in risk assessment.