Genetic variation is necessary factor for continued breeding and increasing genetic gain from selection in crop plants. To evaluate genetic variation and genetic gain from selection in bread wheat, 45 genotypes consisting of 9 cultivars and their 36 crosses were grown in a randomized complete block design with three replications in research farm of Isfahan University of Technology. The phenotypic and genotypic coefficients of variation for grain yield (24.6% and 21.7%, respectively), grain number per main spike (19.6% and 19%), grain weight per spike (19.6% and 19.6%) and biological yield (18.6% and 16.5%) indicated that there is a great degree of variation for these traits in this study. The highest narrow sense heritabilities were belonged to grain number per spike (79%), spike length (62%), 1000 grains weight (58%) and spikeletes per spike (57%). Due to magnitude of heritability of grain yield (18%), its genetic gain (9.12%) was relatively low compared with other traits. The genetic gain for grain number per spike (32.3%), 1000 grain weight (14.3%), and grain weight per spike (12.9%) was larger than other evaluated traits. In general, selection of superior genotypes based on grain number per spike and thousand grains weight could improve grain yield in breeding programs of wheat.
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