Mutagenic activity of dimethyl sulfate on meiosis in M1 sunflower

Abstract

Analysis of changes in the cell nucleus, and especially in its most important structural components – chromosomes, is a reliable test to assess mutagenic susceptibility of plants.

The aim and tasks of the study. The study purpose was to evaluate the effect of mutagen on meiosis in M₁ sunflower cells.

According to the intended purpose, we set the following objectives: To evaluate the effect on supermutagen on the frequency of meiosis disorders, depending on concentration; to compare the incidence of impaired cells in M₁ with the control.

Materials and methods. Two homozygous lines – sterility fixers and 2 lines – pollen fertility restorers bred at the Plant Production Institute nd. a VYa Yuriev were pretreated with chemical mutagen dimethyl sulfate at the concentrations of 0.01% and 0.05% and used as starting material. The controls was dry untreated seeds.

To study meiosis in M₁ sunflower, we separated calathidium segments (d = 2-3 cm) with anthers, fixed them in acetic alcohol (1: 3) for 24 hours. Then we washed them in ethanol three times and stored in 70% ethanol at + 4 ° C. Chromosomes of pollen mother cells were stained in 2% aceto-orcein. Meiosis was studied in temporary preparations squashed in a drop of 40% acetic acid.

Results and discussion. Meiosis disorders in pollen mother cells were mainly expressed in chromosome lag during metaphase or in chromosome disjunction during anaphase. In the 2^nd meiotic division, the chromosome abnormalities observed were essentially the same as those in the 1^st division. Despite the presence of abnormalities in meiosis, externally normally developed tetrads prevailed in mutant sunflower lines. In addition, we observed monads, dyads, triads, pentads, but their percentage was negligible. Having analyzed the data on M₁ sunflower treated with dimethyl sulfate at the concentrations of 0.01% and 0.05%, we can conclude that mutagen significantly affects meiosis in comparison with the control, since the percentage of impaired cells was high as compared to the control. For example, in line Х06-135В the incidence of impairments 0.07%, 6.78%, and 21.01% in the control, with 0.01% DMS, and with 0.05% DMS, respectively, which gives us reason to state that mutagen significantly influences the meiotic processes. Similar results were obtained for the effect of dimethylsulfate on the other three homozygous forms.

Conclusions. From studying chromosome behavior in meiosis of M₁ sunflower treated with 0.01% and 0.05% DMS, we can conclude that the effect of mutagen is significant in comparison with the control, as the percentage of impaired cells was high as compared to the control, as evidenced by statistical processing of the data.  All phases of meiosis in PMC, from start to completion, can be simultaneously observed  in anthers of flowers of a single calathidium.