Developing tools for introgression into wheat where recombination is not possible

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Gene introgression from wild relatives into wheat through recombination relies on the chromosomes of both parents exhibiting synteny along their length. This restricts which wild species can be exploited as a source of important traits as many have rearranged their chromosomes relative to wheat. To exploit the genetic diversity in wild relatives a novel method is needed to facilitate the introgression of beneficial traits to improve wheat.

We propose to develop a novel method by identifying and understanding gametocidal genes, the genes that have been found to be responsible for preferential transfer of segments of wild chromosomes into wheat when using conventional introgression techniques of backcrossing. There are at least two tightly linked genes, termed breaker and inhibitor, which are involved in preferential transmission. This system can be exploited to induce, and recover, translocations between wheat chromosomes and the alien donor. We will study the gametocidal genes on the group 4 chromosomes of Aegilops sharonesis, as they produce a major effect.

The strategy to identify the gametocidal genes is that used to successfully define the Ph1 locus (Griffiths et al 2006). The gene content of the gametocidal region will be established using genome synteny with rice and Brachypodium. This information provides markers with which to saturate the Aegilops sharonensis gametocidal region, thereby providing an initial framework for fine mapping. A physical map of the region covering the gametocidal genes is then established using a BAC library of Aegilops sharonensis. By placing the breakpoints of deletions known to either encompass, or not, the gametocidal genes first onto rice/Brachypodium, and then onto the physical map of the Aegilops sharonensis region, we will define a minimum deletion region containing the gametocidal genes. Sequencing will reveal the gene content of the region and allow us to identify candidates for the breaker and inhibitor genes

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