Preferential intragenomic chromosome pairing in two new diploid intergeneric hybrids between Hordeum and Secale

Abstract

Intergeneric hybrids involving Hordeum californicum with Secale anatolicum and Hordeum bogdanii with Secale cereale ssp. segetale were produced at a frequency of 1.3% of pollinated florets. Chiasmata frequencies of plants ranged from 0.13 to 0.21 per cell in the first hybrid combination and from 0.30 to 0.68 per cell in the second. The paucity of heteromorphic bivalents indicated absence of a close relationship between parental genomes. The associations in bivalents could be classified into Secale-Secale (R-R), Hordeum-Hordeum (H-H), and Secale-Hordeum (R-H) on the basis of difference in size of the chromosomes of Secale and Hordeum. Using a binomial distribution, it is shown that there was preferential intragenomic (R-R, H-H) chromosome pairing, which was attributed to the presence of homologous chromosome segments on nonhomologous chromosomes of the same genome. The distribution of Hordeum and Secale chromosomes to the poles at anaphase occurred at random.