ESTIMATION OF CHROMOSOMAL HOMOLOGY BETWEEN AEGILOPS SPELTOIDES AND THE TETRAPLOID WHEATS BY USING B-CHROMOSOMES

Abstract

In order to estimate chromosomal homology between Aegilops speltoides (genomic constitution SS) and the tetraploid wheats (AABB or AAGG), effects of the B-chromosomes and genotypes of Ae. speltoides on chromosome pairing at MI of meiosis in F₁ hybrids of Ae. speltoides × tetraploid wheats were investigated.
In hybrids with B's, chromosome pairing was strikingly affected by the B's and very small amount of pairing was observed. In hybrids without B's, however, extensive pairing was observed, although the amount of pairing varied due to the speltoides genotypes involved. In these hybrids with or without B's, although some minor yet distinctive differences in pairing attributable to the kind of genomic constitution of the wheat parent were observed in the multivalent frequency and in the distribution (or terminalization) of chiasmata, both hybrids with different genomic constitution (SAB or SAG) had essentially the same amount of pairing. Since the B-chromosomes used did not cause asynapsis (or desynapsis) of homologous chromosomes in Ae. speltoides, the pairing reduced by the presence of B's in the hybrids does not seem to be homologous and is probably homoeologous. Therefore, it can be concluded that there is little chromosomal homology between Ae. speltoides and both tetraploid wheats of genomic constitution AABB and AAGG.