Agro-morphological evaluation of gamma ray-induced mutant populations and isolation of harder grain mutants in wheat (Triticum aestivum L.)

Gamma ray-induced mutations have been widely used to improve existing crop germplasm and create novel genetic variation. In the current study, a multi-year experiment was carried out to induce and isolate mutants with desirable agro-morphological traits and improved grain hardness through evaluation of induced mutant populations generated in soft-textured wheat variety HPW 89 irradiated with gamma ray dose of 250, 300 and 350 Gy. Mutagen sensitivity studies revealed a higher frequency of biological damage and seedling mortality for doses beyond 300 Gy in the M1 generation. However, the mutagenic treatments in the M2-3 populations significantly altered the magnitude of the biometrical traits. Results from the variability and association studies among traits showed that biological yield per plant, 1000-grain weight, spike length, grains per spike and plant height may be prioritized for higher genetic gain and could be used as selection criteria parameters. Multivariate analysis indicated induction of heterogeneity among mutant populations. Overall, 250-300 Gy doses were found ideal for a successful wheat mutation programme and 293 agro-morphologically superior wheat mutants were identified, out of which 108 had semi-hard grain texture based on single kernel characterization system. Among these, nine mutants were found to have the highest grain hardness index due to induced changes in one or both puroindoline genes. Hence, these mutants identified for several traits along with harder grain texture will serve as important genetic resource in future wheat-breeding programmes.