Cytological Irregularities in Hybrids between Species of Wheat with the Same Chromosome Number

Abstract

In hybrids between different 42-chromosome species of wheat a considerable percentage of pollen mother cells show one or a few univalent chromosomes. Such cells are occasionally seen in the pure species but in a much smaller proportion of cases than in the hybrids. The irregularities may be interpreted in essentially the same way as WINGE has interpreted similar phenomena in heterozygous speltoid mutations: with respect to a group of 6 chromosomes vulgare would be ABC/ABC Spelta ABB/ABB(or AB₁B₂/AB₁B₂) and compactum ACC/ACC(or AC₁C₂/AC₁C₂) They may also be interpreted as the result of a more general weakened affinity associated with genetic diversity and not relating to particular pairs of chromosomes.
Hybrids in many combinations between species of the 28-chromo-some group showed only slightly greater amounts of irregularity than the pure species. In special crosses the proportion was much higher. Except in such cases there is no evidence of specific chromosome diversity. Nor is there any evidence of connection between non-homologous chromosomes.