Tools for modifying chromosome pairing and recombination during breeding

Wild relatives of wheat have useful charcteristics such as increased tolerance to drought, salt and cold as well as resistance to various diseases. To meet the requirements of growing wheat under climate change and poor soil conditions, it will become increasingly important to be able to exploit such characteristics by transferring the genes responsible for such traits to wheat. However this transfer into wheat by conventional breeding has previously been very difficult because of the complexity of the wheat genome. Wheat has three sets of genetic information, or genomes, which inherently should make wheat genetically unstable. Stability is conferred by a gene complex, known as Ph1, which effectively prevents recombination of genes across the different genomes. Genes in genome A can only recombine with genes from A, B with B, etc. The good news is that it makes wheat genetically stable. The bad news is it also makes it very hard to get desirable genes from wild species into modern wheat varieties. But now, following extensive research into the Ph1 mechanism, we believe that we know how to temporarily switch off the Ph1 gene complex allowing breeders to transfer in useful 'wild' genes, without upsetting the genetic stability in the field. It will greatly increase the pool of genetic material breeders can use to improve varieties.

Wild relatives of wheat exhibit tolerance to salt, drought and cold as well as resistance to diseases. It would be useful to exploit such traits in wheat breeding. Unfortunately chromosome pairing and recombination of the chromosomes of the wild species and those of hexaploid wheat is suppressed by the activity of Ph1 locus. Moreover hexaploid wheat requires the activity of this locus to stabilise the pairing of the chromosomes of its three genomes and to have a high level of fertility. The molecular and cell biological characterisation of the Ph1 locus reveals that it affects replication and hence chromosome condensation at meiosis. If the chromosomes are not synchronised in their condensation, pairing and recombination can occur between the related chromosomes. The present proposal aims to exploit this information by developing tools which would better enable breeders to exploit the diversity in the wild relatives of wheat within their breeding programmes. We aim to assess whether it is possible to induce homoeologous pairing and recombination in the allopolyploid wheat, and its hybrids, through using drug treatment and genetic transformation. The approach aims to affect through drug treatment or transgenics the cell cycle of meiocytes prior to meiosis, inducing asynchronised condensation of chromosomes at meiosis. If this approach is validated in bread wheat then it should be possible to exploit the same approach for all crops, and therefore enhance the exploitation of wide crossing in plant breeding programmes. This will have significant implications both locally and globally for several agricultural commodities of importance