Gamma Irradiation Induced Chromosome Aberrations in Meiotic Cells of Bread Wheat (Triticum aestivum L.)

Abstract

Background and Objectives: Due to the ever-increasing human population and rapid urbanization, the available agricultural land becomes limited for the production of food grains. As a result, there is an urgent need for creating genetic variability upon which improved varieties could be made. The technology of induced mutagenesis plays an essential role in inducing genetic variations among crop species where hybridization is very challenging. Therefore, the present study has been designed to assess the mutagenic impact of gamma irradiation on the cytological behaviour of T. aestivum L in M1 and M2 generation.
 Materials and Methods: Bread wheat seeds of selected cultivar were irradiated at BARC, Mumbai with five doses. The irradiated and non-irradiated seeds were sown under field condition with three replicates for each dose according to randomized block design to raise the M1 and M2 generations for morphological and meiotic analysis. For meiosis, immature panicles were collected in early morning and immediately fixed in carnoy’s solution for at least 24 hours. Thereafter, anthers from buds were excised and squashed in acetocarmine followed by photomicrography of suitable PMCs to estimate chromosome aberrations.
 Results: The results displayed a progressive elevation in the chromosomal aberrations along with a significant influence on seedling emergence, plant survival and pollen fertility. The most frequent meiotic aberrations detected include chromatin clumping, univalents and early chromosome segregations at metaphase and lagging chromosomes, chromatin bridges and chromosome clumping at anaphase/telophase while unorientation, scattering, polarity disturbances and micronuclei were also noticed. In addition, the frequency of these chromosome aberrations significantly decreased in M2 generation depicting the reclamation in genomic structure.
 Conclusion: The present investigation supports the discovery that gamma irradiations are very effective in creating rapid genetic variability in crop plants including Triticum aestivum which could be essentially exploited for future mutation breeding programmes. The results revealed that the higher treatment doses are toxic whereas lower doses of gamma irradiations seem quite beneficial in generating promising traits with less toxicity. In this study, the cytotoxicity has increased along with gamma irradiation doses and therefore, the genetic structure of the selected bread wheat cultivar is highly affected, which will possibly create new favorable genetic changes in the following generations that would be useful for plant breeders for its improvement.