Bajendra Agricultural University

Comparative cytotoxicity of four herbicides on mitosis and meiosis in maize
--Kumar, M; Kumar, H; Nasar, S

Four herbicides, namely Atrazine, Oxidiazon, Oxyflourfen and Pendiamethaline, were evaluated for their cytotoxic effect on root tip mitosis and PMC meiosis. Two concentrations of aqueous solutions of each herbicide, 5 and 50 ppm, were used for seed treatment for 6 and 12 h. In mitotic studies, 4 h of recovery period was also given, whereas in meiotic studies, treated seeds were directly sown in the field and immature tassels were collected to study PMCs. Root and tassel samples were fixed in 3:1 alcohol-acetic acid and standard 2% acetocarmine squash preparations were made to observe the division rate as well as various chromosomal abnormalities.

Mitotic index was severely affected, and was directly proportional to dose and duration of treatment. Frequency of chromosomal abnormalities varied in different treatments, maximum in Pendiamethaline, followed by Oxyflourfen, Atrazine and Oxidiazon. Both clastogenic and turbagenic types of anomalies were induced by Pendiamethaline, Oxyflourfen and Atrazine, but Oxidiazon induced only binucleate and giant cells (Table 1). Pendiamethaline produced the highest frequency and type of abnormal cells.

The effect of these herbicides on PMCs revealed a dose dependent decrease in cells entering meiotic division (Table 2). The relative efficacy of these herbicides in producing meiotic abnormalities was Pendiamethaline > Oxidiazon > Atrazine > Oxyflourfen. Pollen sterility was also highest in Pendiamethaline treatments. These herbicide treatments led to accumulation of more cells in meiosis I than meiosis II. Arrest of cells at metaphase I and metaphase II was another significant effect observed.

Thus, it appears that the division process in general has been affected by such treatments due to disturbances in normal progression of the nuclear cycle and/or disturbances in the spindle apparatus.

Table 1. Comparative efficacy of different herbicides in maize root tips.

Table 2. Comparative efficacy of different herbicides on maize pollen mother cell meiosis.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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