Metaphase I-bound arms frequency and genome analysis in wheat-Aegilops hybrids. 3. Similar relationships between the B genome of wheat and S or S (l) genomes of Ae. speltoides, Ae. longissima and Ae. sharonensis.

The meiotic behaviour of Triticum aestivum × Aegilops speltoides, T. aestivum × Ae. sharonensis and T. aestivum × Ae. longissima tetraploid hybrids (genome constitution ABDS, ABDS (l) , and ABDS (l) , respectively) has been analysed by the C-banding technique. Of the six types of pairing normally occurring, at metaphase I three were recognized: A-D, AD-BS/AD-BS (l) and B-S/B-S (l) . The relative order observed in the low pairing hybrid, A-D> B-S (l) >AD-BS (l) , as well as that found in high-pairing 'Chinese Spring' × Ae. speltoides hybrids, A-D>AD-BS>ß-S, revealed the existence of preferential pairing patterns among the different genomes that are in competition. In all of the hybrids analysed the mean number of bound arms per cell for the A-D type was significantly higher than the mean number of associations between the B and S/S (l) genomes. Usually the relative contribution of each type of pairing is maintained among hybrids with different Aegilops species. These results indicate that the genomes of Ae. speltoides, Ae. sharonensis and Ae. longissima show a similar affinity with the genomes of hexaploid wheat; therefore none of these species can be considered to be a distinct donor of the B genome of wheats.