Cytogenetic relationships between Avena insularis (2n=28) and both A-strigosa (2n=14) and A-murphyi (2n=28)

The newly discovered tetraploid oat Avena insularis was crossed with the di ploid A. strigosa and the tetraploid A. murphyi. Considerably reduced chrom osome association at meiosis and a low average number of chiasmata per cell of the A. strigosa x A. insularis hybrids indicated that the diploid A. st rigosa did not participate in the creation of A. insularis. From A. murphyi , A. insularis differed by four chromosomal rearrangements and the hybrids between them were sterile. The tetraploids A. magna, A. murphyi and A. insu laris share the two to four floret large diaspore, which is adapted to heav y alluvial soil. They all, however, diverge from one another by four chromo somal rearrangements. At this point it is not possible to determine whether they have diverged from a single tetraploid progenitor, or developed from different diploid species.