Determination of the frequency of wheat-rye chromosome pairing in wheat x rye hybrids with and without chromosome 5B.

Genomic in-situ hybridization (GISH) was used to determine the amount of wheat-rye chromosome pairing in wheat (Triticum aestivum) x rye (Secale cereale) hybrids having chromosome 5B present, absent, or replaced by an extra dose of chromosome 5D. The levels of overall chromosome pairing were similar to those reported earlier but the levels of wheat-rye pairing were higher than earlier determinations using C-banding. Significant differences in chromosome pairing were found between the three genotypes studied. Both of the chromosome-5B-deficient hybrid genotypes showed much higher pairing than the euploid wheat hybrid. However, the 5B-deficient hybrid carrying an extra chromosome 5D had significantly less wheat-rye pairing than the simple 5B-deficient genotype, indicating the presence of a suppressing factor on chromosome 5D. Non-homologous/non-homoeologous chromosome pairing was observed in all three hybrid genotypes. The value of GISH for assessing the level of wheat-alien chromosome pairing in wheat/alien hybrids and the effectiveness of wheat genotypes that affect homoeologous chromosome pairing is demonstrated.