Chromosomal aberration assessment is an important index in mutation breeding for determining the mutagen potency, which helps to deduce an optimum level of mutagen dose tolerable by the species. In this study, the genotoxic effects of ethyl methane sulphonate (EMS), methyl methane sulphonate (MMS) sodium azide (SA), and colchicine were studied on the meiotic cell division of Triticum aestivum L. The results demonstrated that these chemical mutagens cause various types of meiotic anomalies, such as univalents, multivalents, chromosome stickiness, unoriented chromosomes, precocious chromosome movements, chromatin bridges, lagging chromosomes, acentric fragments, and micronuclei. A substantial influence of chromosomal aberrations on the post-meiotic product was also experienced. Irregular sporads in the form of triads, dyads, monads, and polyads, along with regular tetrads were witnessed. The maximum chromosomal aberrations were observed at higher concentrations of the mutagenic treatments. The highest proportion of pollen mother cells showing meiotic aberrations was induced by EMS followed by colchicine, MMS, and SA. The frequency of fertile pollens was seen to decline from control to the highest concentration of mutagens due to anomalies of preceding stages. In addition, mutagenic treatments decreased germination and survival percentage as well. The treatment concentrations ranging from 0.2-0.3% were found favorable in creating significant cytogenetic variability and average lethality and thus, could be beneficial in future cytological and mutation breeding programs.

In this study, cytogenetic toxicity of colchicine in microsporocytes of hard wheat (Triticum durum Desf.) was evaluated. Colchicine treatments revealed the induction of various chromosomal abnormalities in gametic cells which includes chromatin stickiness, unoriented chromosomes, univalents, laggards, bridges, and micronuclei. These abnormalities increased along with increased colchicine concentrations. Simultaneously, the study also deals correlation of overall cytological aberrations with the frequency of seed germination, plant survival, and pollen fertility. Chromosome stickiness along with spindle disturbances, laggards, chromatin bridges, irregular chromosome distribution, and abnormal tetrads are the main causes that lead to a reduction in pollen fertility percentage found in colchicine-treated populations. Furthermore, the colchicine-induced chromosome aberrations caused a significant decline in seed germination and plant survival with the increasing colchicine concentrations. The present findings reveal the potential of colchicine in inducing alterations in chromosome structure and behavior thereby enhancing the genetic diversity in hard wheat. As a result, colchicine could be efficiently exploited for isolating novel and promising mutants in segregating generations.

Induced polyploidy is well known to enhance the genetic architecture of plants that confers better survivorship to them in various agro-climatic conditions than their respective diploids. In this regard, the present study was aimed to obtain the autotetraploid of Commelina benghalensis through antimitotic agent colchicine in order to increase its commercial, ornamental, and medical value. For tetraploidy induction, ungerminated seeds and tips of cotyledon-stage seedlings of the plant were treated with various concentrations of colchicine (0.1, 0.15, 0.2, and 0.25%). Experiments carried out on ungerminated seeds were unsuccessful in generating stable polyploids as it causes the death of germinated seedlings at the very earliest stage. Conversely, applying aqueous colchicine solution constantly on tips of seedlings for 6-8 h per day for three consecutive days was found significant in producing stable tetraploids. Putative tetraploids were subjected to chromosomal, morphological, and palynological observations for their exact confirmation. Out of total 120 seedlings treated, six plants (5%) were found polyploid in C 0 generation with the highest frequency (10%) observed in 0.2% colchicine. During meiosis, the PMCs of tetraploid plants exhibited 44 chromosomes in different associations like quadrivalent, trivalent, bivalent and univalent, while that of the control diploid plants showed regular 11 bivalents. Meiotic analysis showed a constant decrease of quadrivalent frequency and the increasing number of bivalents from C 0 to C 2 for better fertility. Furthermore, differences in vegetative and ornamental characteristics between diploid and polyploid plants were significant. The size of pollen grains, capsules, and seeds were significantly greater than those of diploid plants.

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.