Abstract: Allopolyploidy, involving whole genome duplication (WGD) of interspecific hybrids, is a driving force in the evolution of angiosperms, and has provided favored substrates for the domestication of major agricultural crops. This suggests allopolyploidy is a rich source of genetic variation amenable to natural and artificial selection. While allopolyploidy-induced chromosomal variation is common, its immediate phenotypic effects are challenging to delineate due to the confounding influence of post-polyploidy evolution. Newly constructed allopolyploids, having not yet undergone evolution, present suitable systems to address this issue. In this study, we synthesized five sets of allotetraploids, each with a unique genome constitution of S*S*DD, comprising a common paternal (DD) but distinct maternal (S*S*) parental diploid species of Aegilops. We observed that, except for one sterile synthetic allotetraploid, the remaining four allotetraploids exhibited high fertility, enabling the establishment of sexual lineages through selfing. Chromosomal variation in both number and structure occurred extensively, demonstrating moderate (though variable) effects on key morphological traits related to growth, development, and reproductive fitness of the nascent allotetraploids. All four sets of fertile allotetraploids can be crossed with bread wheat to generate pentaploid F₁ hybrids, which as maternal parents can be further backcrossed to bread wheat. This approach promises a feasible strategy for the concomitant introgression of the vast repertoire of genetic variation from the D- and each of the four S* genome-containing species to bread wheat.

Key words: allopolyploidy, karyotypic variation, phenotypic effects, introgression, wheat