Dissecting genotype-by-environment interactions and genetic diversity in gamma irradiation-derived bread wheat...

Climate change and escalating biotic pressures, particularly stripe (yellow) rust, present major challenges to sustainable wheat production in India and globally. To enhance genetic diversity and introduce novel variations, this study utilized mutation breeding by subjecting seeds of the popular wheat variety DBW88 to gamma irradiation. Following rigorous selection through successive generations, twenty promising mutant lines alongside their parent and commercial checks (HD2967, HD3086, WH1105) were evaluated over three consecutive crop seasons under multi-environment trials. The genotypes were screened for different agronomic traits and field resistance against yellow rust using Adult Plant Resistance (APR) and Seedling Resistance Tests (SRT). Phenotypic stability and genotype-by-environment interactions (GEI) were analyzed via Additive Main Effects and Multiplicative Interaction (AMMI) models, GGE biplots, and superiority index, while molecular diversity was assessed using Kompetitive Allele-Specific PCR (KASP) SNP markers. The results revealed highly significant effects of genotype, environment, and GEI on grain yield. Thus, the use of gamma radiation is effective in improving the desirable traits, including grain yield. The mutant line DTWM-16 exhibited the highest baseline superiority and yield stability across environments, followed closely by check WH1105 and mutant DTWM-15. Under stressful environments, DTWM-08 and DTWM-16 demonstrated exceptional localized adaptation. Disease screening revealed that 34% of the mutants (including DTWM-03 and DTWM-08) achieved complete rust immunity, successfully breaking the high susceptibility of the parental line DBW88. Furthermore, molecular profiling indicated a narrow overall genetic base, conserving elite parental structures; however, mutants DTWM-10 and DTWM-14 emerged as distinct, highly divergent outliers with unique allelic combinations and heterozygosity patches. In conclusion, this study confirms that induced mutagenesis effectively balances yield stability and robust disease resistance. It is suggested that these traits can be improved beyond the performance of corresponding traits in their parent genotypes. Elite mutants like DTWM-08 and DTWM-16 are excellent candidates for regional cultivation, while divergent mutant lines DTWM-10 and DTWM-14 provide valuable genetic resources for future hybridization panels to broaden the wheat gene pool. The newly produced mutants can also be used to explore the genetic mechanisms of complex traits in the future.