Cloning and mode of action of the major interspecific crossability locus (Kr1) in wheat

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The genetic diversity available to breeders within wheat is very limited compared to that available within cultivated and related wild relatives of wheat. However a number of barriers need to be overcome in order to have access to the full range of diversity within the wild species and to exploit this by introducing desirable genes from this exotic germplasm. The first barrier can be the failure of pollen from wild species to fertile the wheat ovary. Although wheat can be crossed with a wide range related species, most adapted wheat varieties are incompatible because of the failure of the pollen to fertilise the ovary. The biological basis for this failure of pollen from wild relatives to penetrate the wheat style and ovary remains to be elucidated. The present proposal addresses this issue. Kr1 gene on wheat chromosome 5B has the largest effect in inhibiting the ability to make crosses with most related species, for example rye and Hordeum bulbosum. We aim by the end of this project to have identified a candidate gene for Kr1 on wheat chromosome 5B. This will be achieved by exploiting the variability in crossability from the presence of the dominant (non-crossable) allele in wheat Hobbit variety and the recessive (crossable allele) in the variety Chinese Spring (CS). Kr1 will be fine mapped using single chromosome recombinant lines involving Hobbit (CS5B). Synteny with rice and Brachypodium genomes, and the building and sequencing of a wheat contig to region defined as containing Kr1 will reveal a candidate for the gene.

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