ABSTRACT
A stable interspecific sexual plant hybrid between Hordeum vulgare cv. Tuleen 346 (barley) × H. bulbosum was shown to have seven chromosomes originating from each parent by genomic in situ hybridization. Electron microscope serial thin-section reconstructions of metaphases and comparison with light micrograph karyotypes enabled chromosomes to be identified from their morphology. The three-dimensional positions of their centromeres were established and analysed in the reconstructions of somatic root tip metaphases and cells at mitotic metaphase near their entry into meiosis. Parental genomes tended to lie in spatially separated domains in both tissues. Although varying in morphology, the two sets of chromosomes had similar mean sizes, so size differences did not cause the separation observed. In the EM, the centromere-associated structures of the chromosomes of the more central genome, originating from H. vulgare, were larger than those of the more peripheral genome of H. bulbosum origin.
