Genetic variation and genetic gain from selection in bread wheat

Genetic variation is necessary factor for continued breeding and increasinggenetic gain from selection in crop plants. To evaluate genetic variation andgenetic gain from selection in bread wheat, 45 genotypes consisting of 9 cultivarsand their 36 crosses were grown in a randomized complete block design with threereplications in research farm of Isfahan University of Technology. The phenotypicand genotypic coefficients of variation for grain yield (24.6% and 21.7%,respectively), grain number per main spike (19.6% and 19%), grain weight perspike (19.6% and 19.6%) and biological yield (18.6% and 16.5%) indicated thatthere is a great degree of variation for these traits in this study. The highest narrowsense heritabilities were belonged to grain number per spike (79%), spike length(62%), 1000 grains weight (58%) and spikeletes per spike (57%). Due tomagnitude of heritability of grain yield (18%), its genetic gain (9.12%) wasrelatively low compared with other traits. The genetic gain for grain number perspike (32.3%), 1000 grain weight (14.3%), and grain weight per spike (12.9%) waslarger than other evaluated traits. In general, selection of superior genotypes basedon grain number per spike and thousand grains weight could improve grain yield inbreeding programs of wheat.