Cytogenetic events in the endosperm of amphiploid Avena magna × A. longiglumis.

This study analysed cytogenetic events occurring in the syncytial endosperm of the Avena magna H. C. Murphy & Terrell × Avena longiglumis Durieu amphiploid, which is a product of two wild species having different genomes. Selection through the elimination of chromosomes and their fragments, including those translocated, decreased the level of ploidy in the endosperm below the expected 3n, leading to the modal number close to 2n. During intergenomic translocations, fragments of the heterochromatin-rich C-genome were transferred to the D and Al genomes. Terminal and non-reciprocal exchanges dominated, whereas other types of translocations, including microexchanges, were less common. Using two probes and by counterstaining with DAPI, the A. longiglumis and the rare exchanges between the D and Al genomes were detected by GISH. The large discontinuity in the probe labelling in the C chromosomes demonstrated inequality in the distribution of repetitive sequences along the chromosome and probable intragenomic rearrangements. In the nucleus, the spatial arrangement of genomes was non-random and showed a sectorial-concentric pattern, which can vary during the cell cycle, especially in the less stable tissue like the hybrid endosperm.