Loss of genetic integrity in artificially aged seed lots of rice (Oryza sativa L.) and common bean (Phaseolus vulgaris L.).

Loss of genetic integrity can occur during the long-term conservation of seeds. We have studied these effects in seeds of rice (Oryza sativa L.) and common bean (Phaseolus vulgaris L.) exposed to accelerated aging (elevated temperature and moisture) conditions. Tests of first count, germination, and germination speed index were performed to measure physiological quality; cytogenetic tests and comet assay were used to evaluate genetic integrity. With aging, we observed a decrease in mitotic index and an increase in the frequency of chromosomal alterations in root cells of imbibed seeds, as well as increased DNA damage (comet assay) in dry and imbibed seed embryos of both species. The comet assay can be a useful technique for measuring genetic integrity in seed conservation programs.

Comet and cytogenetic tests as tools for evaluating genomic instability in seeds of Oryza sativa L. and Phaseolus vulgaris L. from gene banks.

This study aimed to assess the feasibility of comet and cytogenetic tests as tools for evaluating genomic instability in seeds of Oryza sativa L. (rice) and Phaseolus vulgaris (beans) L. from gene banks. Rice and beans were exposed to methyl methanesulfonate (MMS) as a reference DNA damaging agent. Seeds of two accessions of rice and beans were obtained from Embrapa Rice and Beans - Brazil. Seed groups were imbibed in three concentrations of MMS for three periods of time to carry out cytogenetic tests, and for one period for the comet test. At concentrations of 10 and 15 mg/L, MMS induced cytotoxic and/or mutagenic effects in the meristematic cells of roots from all the accessions of both species. In the comet test, MMS induced genotoxic effects at all the concentrations in the evaluated accessions of rice and beans, except in one accession of beans at the lowest concentration (5 mg/L). Both species showed sensitivity to MMS. The comet test can be proposed for the measurement of genomic instability in accessions of rice and beans in gene banks, as being more sensitive than the cytogenetic tests used.

Comet and cytogenetic tests as tools for evaluating genomic instability in seeds of Oryza sativa L. and Phaseolus vulgaris L. from gene banks

Abstract This study aimed to assess the feasibility of comet and cytogenetic tests as tools for evaluating genomic instability in seeds of Oryza sativa L. (rice) and Phaseolus vulgaris (beans) L. from gene banks. Rice and beans were exposed to methyl methanesulfonate (MMS) as a reference DNA damaging agent. Seeds of two accessions of rice and beans were obtained from Embrapa Rice and Beans - Brazil. Seed groups were imbibed in three concentrations of MMS for three periods of time to carry out cytogenetic tests, and for one period for the comet test. At concentrations of 10 and 15 mg/L, MMS induced cytotoxic and/or mutagenic effects in the meristematic cells of roots from all the accessions of both species. In the comet test, MMS induced genotoxic effects at all the concentrations in the evaluated accessions of rice and beans, except in one accession of beans at the lowest concentration (5 mg/L). Both species showed sensitivity to MMS. The comet test can be proposed for the measurement of genomic instability in accessions of rice and beans in gene banks, as being more sensitive than the cytogenetic tests used.

Genotoxicity of sodium metabisulfite in mouse tissues evaluated by the comet assay and the micronucleus test.

Sodium metabisulfite (SMB, Na(2)S(2)O(5)) is widely used in the food and pharmaceutical industries, because of its ability to inhibit proliferation of microorganisms and its antioxidant properties. We have evaluated the genotoxic effects of SMB on different tissues of the mouse, by use of the comet assay (liver and blood cells) and the micronucleus test (blood and bone marrow cells). For all tissues, significant increases in damage index and damage frequency values were observed in the SMB-treated groups (1 and 2g/kg doses) compared to the control animals. The Kruskal-Wallis test showed that the mean micronucleus frequencies in peripheral blood and bone marrow cells of mice treated with the highest dose of SMB (2g/kg) showed significant increases, when compared with controls, and a significant reduction in the ratio of polychromatic to normochromatic erythrocytes was also seen. No difference in results between sexes was observed. Our results show that high oral doses of SMB may pose a genotoxic risk.