Gamma radiation-induced variation in wheat (Triticum aestivum L.) mutants for yield and agronomic traits

Gamma irradiation is a widely used mutagenic tool for creating genetic variability and improving crop plants. The present study evaluated the effects of different doses of gamma irradiation on phenological, morphological, and yield-related traits in two wheat (Triticum aestivum L.) genotypes, TD-1 and NIA-Amber. Dry seeds were irradiated with cobalt-60 gamma rays at doses of 100, 200, 300, and 400 Gy, while untreated seeds served as control. The treated and control seeds were planted in a randomized complete block design (RCBD) with three replications under field conditions at the Nuclear Institute of Agriculture (NIA), TandoJam, Pakistan. Total of 13 traits were recorded, including days to heading, days to maturity, plant height, spike length, peduncle length, spikelets per spike, grains per spike, grain weight per spike, grain yield per plant, 100-grain weight, biological yield, and harvest index. Analysis of variance (ANOVA) revealed highly significant (p<0.01) effects of genotype, dose, and their interactions for most traits. Higher doses (300–400 Gy) caused delays in heading and maturity, reduced plant height, spike length, peduncle length, and negatively impacted yield-related parameters. Conversely, moderate doses (100–200 Gy) maintained relatively better performance and induced beneficial variability. The results indicate that gamma irradiation, at optimized doses, can generate useful genetic variability for wheat improvement. Genotype × dose interactions highlighted the differential response of TD-1 and NIA-Amber, suggesting that selection of promising mutants from moderate doses could contribute to yield stability and adaptability. The findings confirm that while excessive doses of irradiation are detrimental, carefully selected lower doses can serve as an effective breeding tool to broaden the genetic base of wheat for future crop improvement programs.