Optimized gamma radiation produces physiological and morphological changes that improve seed yield in wheat

Deciphering induced variability, character association and multivariate analysis utilizing gamma rays and ethyl methanesulfonate in bread wheat (Triticum aestivum L.) genotypes with differential grain texture

PURPOSE

Sustainable wheat production and higher genetic gains can be realized by broadening the genetic base and improving the well adapted varieties. In the present study, a multi-year experiment involving induced mutagenesis was conducted to create genetic variation, assess trait associations and genetic divergence in four wheat varieties with differential grain texture treated with six doses of gamma rays and ethyl methane sulfonate using ten agro-morphological traits.

MATERIALS AND METHODS

Healthy selfed seeds of four bread wheat varieties with differential texture were irradiated using six doses ranging from 175 Gy-300 Gy of gamma rays (Co60: BARC, Mumbai) and six concentrations of ethyl methanesulfonate (0.3-1.3%) (Sigma-Aldrich, Bangalore, India) to evaluate variability, character association and degree of genetic diversity induced among the mutagenic treatments of wheat varieties with differential grain texture.

RESULTS

Significant inter-population differences were observed for almost all the traits. The sample mean of twelve mutant populations in each of the cultivar exhibited superior quantitative phenotypic traits and increased values of the genetic parameters. Based on association and variability studies, plant height, spike length, grain filling period, biological yield per plant and harvest index can be used as early generation criteria for maximum genetic improvement. Multivariate studies indicated the contribution of various traits towards divergence and indicated the efficiency of mutagens in generating variability. Gamma-irradiation dosages between 200-250 Gy and 0.5-1.1% EMS for soft-textured varieties, whereas doses between 225-275 Gy and 0.5-0.9% EMS were found to be most potent for semi-hard-textured varieties.

CONCLUSIONS

Assessment of mutagen sensitivity showed that semi-hard wheat varieties were responsive to both mutagens, particularly EMS and generated higher variability and divergence than the soft textured varieties. Hence, gamma rays were proved to be more effective in generating higher variability than ethyl methanesulfonate. A total of 117 putative mutants were identified with desirable agro-morphological attributes. Among these, mutants with higher inter-cluster distance can be used as parents in hybridization programs and serve as important genetic resources in future wheat improvement programs.

Winter wheat cytogenetic variability under the action of a chemical supermutagen

The analysis of cytogenetic activity is a key component in determining prospects of future hereditary variability after, subject to a certain mutagenic factor, primarily identifying the significance of the genotype-mutagenic interaction, the correctness of the selected concentrations for more thorough screening of some development parameters. Winter wheat seeds of eight varieties (Balaton, Borovytsia, Zeleny Gai, Zoloto Ukrainy, Kalancha, Niva Odeska, Polyanka, Pochayna) were subjected to ЕМS (ethylmethansulfonate) at the concentrations of 0.025%, 0.05%, 0.10% The exposure lasted for 24 hours. Cytogenetic analysis was carried out for pollen fertility; we also examined the rates and spectras of chromosomal rebuildings in proper cell devision phases in relation to plant gcnotype and concentration of the mutagen. The experiment was aimed at identification of interrection between geotype, concentration of mutagen and mutagen nature, determining genome response to mutagen action. Such indicators of cytogenetic activity as the total rate of chromosomal abnormalities, fragments and double fragments, single and double bridges, micronucleus and lagging chromosomes were studied. The selected concentrations of the mutagen significantly influenced all the analyzed parameters, they can be attributed to the optimal and high range of concentrations according to the nature of the impact on bread wheat. We determined that in the case of the mutagenic action, the genotype had a significantly lesser effect on the nature and rate of individual aberrations than an increase in the concentration, while having a significant effect on the rate of increase in pollen sterility. The mutagen was characterized by a significantly lower site-specificity at the cellular level than other chemical supermutagens, manifesting only in the correlation between individual types of aberrations, but not in the character of the increase in their number. The key parameter to identify the activity of this agent was the frequency of fragments and double fragments, their ratio with bridges.