Evaluation of cytogenetic effects of deltamethrin in root meristem cells of Allium sativum and Allium cepa: A possible mechanism of chromosome damage

Abstract

To establish the use of Allium sativum as a sensitive test model for genotoxicity, cytogenetic effects of commercially formulated deltamethrin were examined through chromosomal and mitotic aberrations in the root meristem cells of A. sativum and Allium cepa. Ultraviolet (UV) and Fourier transform infrared (FTIR) spectral measurements were also carried out to understand the interaction of deltamethrin with DNA. Test concentrations of deltamethrin 0.06, 0.12, 0.25, 0.5, 1, or 2 mg kg⁻¹ were mixed in soil and the garlic cloves/onion bulbs were placed over deltamethrin-contaminated soil. Some roots were sampled at 48 h exposure and other intact roots were washed thoroughly with distilled water and left for 48 h recovery in normal soil. Cells analyzed immediately after the exposure showed a significant, concentration-dependent inhibition of mitotic index (MI) and induction of mitotic and chromosomal aberrations (MA and CA) in both the test systems. The observed CA and MA were relatively higher in A. sativum system compared to A. cepa. The 48 h recovery period reduced the effect of the test compound on % aberrations; however, cells exposed to 1 and 2 ppm showed a significant frequency of aberrations despite the recovery period. Data indicate that higher concentrations of deltamethrin induce CA and MA in A. sativum and A. cepa. The present study demonstrates greater sensitivity of A. sativum versus A. cepa and may be used as a sensitive and reliable test system for environmental monitoring. A bathochromic shift observed in UV absorption spectra reveals that deltamethrin binds with DNA. Role of vibrational modes of the active site in the recognition (via polarization) and reaction of deltamethrin with DNA was described. Based on data of valence charge distributions on the atoms of deltamethrin, spectroscopic studies and structural properties, a possible mechanism was proposed for the interaction of deltamethrin with DNA resulting in chromosomal damage.

Keywords:

• deltamethrin
• Allium sativum and Allium cepa
• FTIR and UV spectrum
• deltamethrin-DNA interactions
• molecular orbital calculations
• chromosome breaks

Acknowledgements

Authors are grateful to the Director, I.I.T.R, Lucknow, India for his keen interest and constant support in the present study. Authors are also thankful to Prof. P. Tandon for the computation by the Gaussian programme and Mr Neeraj Mathur for expert statistical analysis in this study. IITR Communication No. 2659.