| Summary: | In this article we report the results of our investigation of cytogenetic parameters of changes in the chromosomal complex of new Ukrainian winter wheat varieties and some relationships between values of cytological indexes and different concentrations of DAB (1,4-bis-diazoacetyl butane). Analysis of chromosomal aberrations following mutagenic action of any kind of mutagen by the anaphase method is one of the most widely investigated and most precise methods which can be used to determine the fact of mutagenic action on plants and identify the nature of the mutagen. We combined in our investigation sensitivity of genotype to mutagen using cytological analysis of mutagen treated wheat populations with the corresponding different varieties by breeding methods to reveal their connections and differences, specific sensitivity to mutagenic action on the cell level. Dry seeds of 7 varieties and 1 line of winter wheat were subjected to DAB in 0.1% and 0.2% concentration, which is standard practice for mutation breeding of winter wheat. We investigated rates and spectra of chromosomal aberrations in the cells of the primary root tips of winter wheat during mitosis. The coefficient of correlations between the rate of chromosomal aberrations and the concentration of DAB was at the level 0.6%. Fragments/bridges ratio is a clear and sufficient index for determining the nature of the mutagen agent. We distinguished the following types of chromosomal rearrangements: chromatid and chromosome bridges, single and double fragments, micronuclei, and lagging chromosomes. Investigation of DAB action confirmed the reliability of the fragments-bridges ratio (prevalence of fragments over bridges for chemical mutagens and vice versa for gamma-rays) for identification of the nature of the mutagen. Complicated (or combined) aberrations, micronucleus, lagging chromosomes were not observed for some varieties under DAB action. Genotypes selected after action of chemical mutagens are less sensitive to recurrent mutagenesis with chemical mutagens.
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