Chromosome pairing between Hordeum and wheat can be promoted in the absence of the Ph1 locus

Abstract

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 iploids during meiosis (each chromosome only pairs with its identical, homologue, and not with related or homoelogous chromosomes). Chromosome pairing is controlled in wheat by the Ph1 locus, which suppresses homoeologous chromosome pairing. Therefore the hybridization be tween 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 germplas m carrying introgressions from Hordeum chilense, a wild barley with high potential for wheat breed ing 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.