Synthetic polyploid lines have been used to introduce agriculturally important genes from wild relative species to bread wheat. They have provided useful materials not only in wheat breeding but also in wheat evolution studies. Here, we report the production of more than 150 synthetic allohexaploid wheat lines through artificial interspecific crosses of a durum wheat cultivar Langdon (AABB genome) with various wild diploid relatives including the Am-, D-, M-, N-, and Ugenome species. All lines having the D or N genome were obtained through spontaneous genome doubling through the union of unreduced gametes formed in the ABD- or ABN-genome F1 hybrids, whereas most of other lines were produced via colchicine treatment of the F1 hybrids. The existence of the diploid relative’s genomes in those lines was confirmed by genomic in situ hybridization and/or PCR analysis with genome-specific markers that were developed using RNA sequencing data of Langdon and the diploid relatives. Various types of hybrid growth abnormalities, such as hybrid necrosis, hybrid chlorosis, hybrid dwarf, grass-clump dwarf and severe growth abortion, were observed in the triploid F1 hybrids between Langdon and the diploid species. The occurrence of hybrid growth abnormalities appeared to depend on the genotypes of the parental diploid species. Furthermore, the synthetic lines showed phenotypic differences in flowering time, plant height, spike shape and grain shape. Some of the differences appeared to reflect the phenotypic variation in the parental diploid species. Interestingly, the synthetic lines greatly varied in grain hardness measured using the singlekernel characterization (SKCS) system. Synthetic lines with the Am and D genomes generally showed soft kernel texture, whereas the grains of all synthetic lines with the U genome were hard in texture. Consistent with this observation, scanning electron microscope observation of the transverse seed sections revealed clear difference in the surfaces of starch granules in endosperm between soft- and hard-type grains. The hard texture of the synthetic lines having the U genome seems to be largely caused by the absence of the transmission of functional PINA and PINB proteins from the Ugenome donors.The synthetics with the M and N genomes also included soft and hard kernel texture lines. Thus, some grain-related traits of the wheat diploid relatives were efficiently evaluated using the synthetic hexaploid lines. Therefore, the synthetic lines are useful for functional evaluation of wild relatives-possessing genes under the allohexaploid genetic backgrounds.