Chromosome Pairing Between Wheat and Hordeum chilense Chromosomes is Promoted in the Background of ph1 Mutants

Wheat is an allopolyploid which has two or more sets of related chromosomes as the result of doubling chromosomes following sexual hybridization between closely related species. Hexaploid (bread) wheat contains A, B and D genomes and tetraploid (pasta) wheat contains A and B genomes. Despite their genome complexity, wheat behave as diploids during meiosis (each chromosome only pairs with its identical, homologue, and not with related or homoeologous chromosomes). Chromosome pairing is controlled in wheat by the Ph1 locus, which suppresses homoeologous chromosome pairing. Therefore the hybridization between polyploid wheat and related species caused inter-specific hybrids without chromosome pairing between wheat and related species. However, in the absence of the Ph1 locus (ph1 mutant) the chance of pairing between related chromosomes is increased. In this work, we exploit the ph1 mutant to development new wheat germplasm carrying introgressions from Hordeum chilense, a wild barley with high potential for wheat breeding due to its agronomical traits such as resistance to some diseases or high antioxidant content. In the absence of the Ph1 locus chromosome specificity has been suppressed in this project, allowing inter-specific chromosome associations between wheat and H. chilense for the first time. Chromosome pairing and recombination between H. chilense and wheat chromosomes were detected by genomic in situ hybridization. A summary of the breeding program carried out to transfer desirable agronomic traits from H. chilense into wheat is reviewed in this work.