Nevertheless, from this plethora of QTLs, few loci/genes have been cloned by map-based cloning approaches mainly because of the large and complex hexaploid genome (~17 Gb) that consists of three homeologous genomes (A, B, D) and an abundance of repeat sequences (80%) . Studies on comparative genomics have shown high synteny and collinearity among different grass genomes, such as those of wheat, barley, rice, millet, maize and sorghum. This pattern of genome organization in the members of the grass family provides a powerful approach for gene discovery in common wheat . A large number of genes have been discovered in common wheat by synteny-based cloning, in which the gene sequences of model crops such as rice and barley have been used as references to identify orthologous genes in wheat. For example, the genes TaTGW6 [16, 17], TaCwi-A1 , TaSus2-2B , TaSus2-2A, TaSus1-7A , TaGW2-6A, 6B [9, 12, 21], TaCKX6-D1 , TaSAP1-A1 , TaGS1a , TaGS-D1 , and TaGASR-A1  were discovered using rice-wheat synteny and using molecular markers in marker-assisted wheat breeding. Hence, the isolation and characterization of genes controlling grain size in common wheat will help breeders maximize yield potential by establishing gene-based breeding programs.