Univalent-dependent meiotic nonreduction, which leads to the production of unreduced gametes, is thought to be the predominant mechanism underlying allopolyploid plant formation. However, little is known about the underlying cytological mechanism. In the present study, we observed male sporogenesis in F1 amphihaploid hybrids of wheat–rye by FISH with the help of diagnostic PrCEN-1 specific for the rye centromere. Our observations indicated that at meiotic metaphase I, the chromosomes were accumulated on the equatorial plate. At this stage, the elongated centromeres were amphitelically oriented perpendicular to the equatorial plate, indicating tension from opposite poles. At late metaphase, the centromeres and sister chromatids started separating. Subsequently, the sister chromatids and centromeres split finally resulting in dyads. Our observations indicate that bipolar orientation of the sister kinetochores of univalents at the equatorial plate in metaphase I is important for the subsequent bipolar separation of sister chromatids in the first meiotic division. Allopolyploids are common in plants. Wide hybridization, the first step for the origination of allopolyploids, brings divergent genomes from different species together into an amphihaploid hybrid. Because only one set of homologous chromosomes is present, amphihaploids (analogous to haploid plants) are usually sterile due to reduced meiosis. Meiotic nonreduction (meiotic restitution), however, can lead to production of functionally unreduced gametes, and their union immediately generates an amphidiploid (allopolyploid). Meiotic nonreduction is thought to be the