A field experiment was performed during season 2018/2019 at the Experimental Farm, Faculty of Technology and Development, Zagazig University. Four diverse bread wheat genotypes i.e (Gemmeiza 11, Sids12, Shandaweel-1and Sahel-1), were involved in the present study and treated with different doses of gamma rays, i.e. (0, 150, 250 and 350 Gy) under water stress treatment it was irrigated immediately after sowing and first irrigation was after 45 days for sowing and second irrigation up to flowering stage. to study mean performance and genetic variability in M2 generation influenced by gamma rays.
Results showed that subjected wheat varieties to gamma rays  doses resulted a significant variation for No. of spikes/plant, spike grain weight/gm. and  No. of grains/pike,  but non-significant for grain yield /plant  in all cases revealing the great influence of the gamma rays doses on genetic makeup of wheat varieties. Mean performance for grain yield/plant (g.) in M2 generation for wheat cultivars changed from 14.49 (g.); (Sahel-1) to 19.35 (g.); (Gemmieza-11). Regarding mean effects of gamma rays doses it ranged from 15.22 (g),  (350 Gy) to 17.56 (g.) (150 Gy). PCV was relatively higher than its respective GCV for spike length, No. of spikes /plant, No. spikelets / spike,   No. of infertile spikelets/spike, No. of fertile spikelets/spike, spike grain weight and grain yield/plant, indicating their influenced by the mutagen changes. Whereas, narrow difference between PCV and GCV was for No. of grain /spike and 1000- grain weight which coupled with ECV estimates. Heritability in broad sense, was high ( ≥ 75) for spike length, spike grain weight, no. of grain /spike and 1000-grain weight. With highest of genetic advance for no. of infertile spikelets/spike.  Whereas, moderately it was for spike length, no. of tillers /plant, no. of grain /spike, spike grain weight, 1000-grain weight and grain yield/plant, indicating greater scope for selection and improvement of these traits under water stress direction.
Conclusively, the use of gamma rays its importance of influence mutation in some wheat genotypes, indicated greater scope for selection and improvement of wheat traits under water stress direction.