Developing tools for introgression into wheat where recombination is not possible

该项目将解决一个重要问题，该问题阻碍了小麦野生近缘种遗传多样性的开发。能够与野生近缘种一起工作，从而将有益的性状引入小麦将是一项重大的科学成就，并将极大地改善育种者培育性能更高的小麦新品种的方式。一些野生近缘种适应于在不同的气候条件下茁壮成长，或者它们具有对重要疾病的天然抗性和/或具有可能影响产量的其他重要特征。我们想做的是生产出能够利用这种多样性的工具，并将这些有利的特征遗传地引入小麦。通过这样做，我们将使小麦育种者能够以可持续的方式改善小麦性能，增加产量，引入抗病和抗旱能力。在少数情况下已经做到了这一点。如何阻止其他野生近亲被利用？原因是基因顺序的相似性，特别是在染色体末端（端粒），是必要的，以使染色体在减数分裂过程中有效地排列和重组。没有重组，就没有机会将野生近缘种的遗传多样性引入小麦。重组在某些情况下是可能的，但与小麦染色体相比，许多野生近缘种已经重新排列了它们的染色体，这使得基因转移变得困难，如果不是不可能的话，在减数分裂期间进行重组。那么我们如何克服这个问题呢？我们想要做的是利用在一些野生物种中发现的特殊基因，即所谓的杀配子基因。这些基因是在培育小麦品系时发现的，这些小麦品系有一条来自野生亲缘关系的额外染色体片段，因为发现野生亲缘关系的一些染色体优先传递给后代。这些染色体被称为“杜鹃”染色体（或配子体染色体）。这些染色体上的杀配子基因诱导染色体断裂，这经常导致小麦和野生品种染色体之间的易位或交换。这一策略为基因从野生物种的染色体转移到小麦提供了一条途径。然而，它是费力的，需要丰富的细胞遗传学经验。我们想要更聪明地使用这个系统，所以我们需要了解它的生物学基础，因此这个项目的目的是确定负责控制沙龙盾4S染色体上的配子体杀伤效应的基因。目前所有的育种都是基于染色体分类和染色体进行减数分裂重组的能力。确定杀配子体效应的生物学基础将使替代系统能够更有效地开发和应用于植物育种。这将最终提高小麦的遗传多样性，特别是可用于小麦改良的野生物种库。

This project will address an important problem which has hampered the exploitation of the genetic diversity held within wild relatives of wheat. Being able to work with wild relatives so that beneficial characteristics can be introduced into wheat will be a major scientific achievement and dramatically improve the way breeders can generate new varieties of wheat with increased performance. Some wild relatives are adapted to thrive under different climatic conditions to that of domestic wheat, or they carry natural resistance to important diseases and/or carry other important characteristics which could influence yield. What we want to do is to produce the tools which will allow the exploitation of this diversity and genetically introduce these favourable characteristics into wheat. In doing so we will be enable wheat breeders to, amongst other things, improve wheat performance in a sustainable way, increase yield, introduce disease resistance and drought tolerance. In a small number of cases this has already been achieved. What stops other wild relatives being used? The reason is that similarity of gene order, particularly at the chromosome ends (telomeres), is necessary to allow the chromosomes to align efficiently and recombine during the process of meiosis. Without recombination there isn't the opportunity to introduce the genetic diversity of wild relatives into wheat. Recombination Is possible in some cases but many wild relatives have rearranged their chromosomes compared with wheat chromosomes, making gene transfer difficult, if not impossible, by recombination during meiosis. So how can we overcome this problem? What we want to do is to exploit special genes, known as gametocidal genes that are found in some wild species. These genes were discovered when breeding to produce wheat lines that had an additional segment of a chromosome from a wild relative, because some chromosomes from the wild relative were found to transmit preferentially to the offspring. These chromosomes have been termed 'cuckoo' chromosomes (or gametocidal chromosomes). Gametocidal genes on these chromosomes induce chromosomal breakages which frequently result in translocations, or exchanges, between the chromosomes of wheat and those of the wild species. This strategy provides a route for the transfer of genes from chromosomes of wild species into wheat. However it is laborious and requires extensive experience in cytogenetics. We want to be smarter in the use of this system and so we need to understand its biological basis therefore the aim of this project is to identify the genes responsible for controlling the gametocidal effect on the 4S chromosome of Aegilops sharonensis. All breeding is currently based on chromosome assortment and the ability of chromosomes to undergo meiotic recombination. Identifying the biological basis for the gametocidal effect will enable an alternative system to be more effectively exploited and deployed in plant breeding. This will ultimately enhance the genetic diversity in wheat and in particular the pool of wild species which can be exploited for wheat improvement.