To analyze genetic diversity and to estimate heritability and genetic gain of bread wheat recombinant inbred lines (RILs), 79 RILs derived from a cross between a commercial variety Yecoro Rojo and NO.49 an Iranian local genotype were assessed using square lattice design under normal and water deficit conditions. Combined analysis of variance revealed significant differences among lines for all the studied traits, whereas line and the irrigation interaction was not significant. Among the measured traits, grain yield, number of spikes per square meter, number of grain per spike, plant height and harvest index showed higher phenotypic and genotypic coefficient of variation. Narrow-sense heritability ranged from 38.04 for number of grain per spike to 86.25 for 1000-grian weight. Expected genetic gain was varied from 7.10% (day to heading) to 29.83% (harvest index).
