Developing tools for introgression into wheat where recombination is not possible

该项目将解决阻碍开发野生近缘小麦遗传多样性的一个重要问题。能够与野生近亲合作，从而将有益的特征引入小麦将是一项重大的科学成就，并极大地改进育种者培育性能更好的新小麦品种的方式。一些野生近缘小麦适应于与国内小麦不同的气候条件，或具有对重要疾病的天然抗性和/或具有其他可能影响产量的重要特征。我们想要做的是生产工具，允许利用这种多样性，并从基因上将这些有利的特征引入小麦。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表现，增加产量，引入抗病和抗旱。在少数情况下，这一点已经实现。是什么阻止了其他野生亲戚被利用？这是因为基因序列的相似性，特别是染色体末端(端粒)的相似性，是使染色体在减数分裂过程中高效配对和重组所必需的。如果没有重组，就没有机会将野生近缘的遗传多样性引入小麦。重组在某些情况下是可能的，但许多野生近缘植物的染色体与小麦染色体相比已经重新排列，这使得在减数分裂期间通过重组进行基因转移即使不是不可能，也是困难的。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。这些基因是在培育含有来自野生亲缘关系的额外染色体片段的小麦品系时发现的，因为发现来自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(或杀配子染色体)。这些染色体上的杀配子基因导致染色体断裂，这经常导致小麦和野生物种的染色体之间的易位或交换。这一策略为将野生物种染色体上的基因转移到小麦中提供了一条途径。然而，它是费力的，需要在细胞遗传学方面有丰富的经验。我们希望更智能地使用这个系统，因此我们需要了解它的生物学基础，因此本项目的目的是鉴定负责控制沙毛山羊草4S染色体上的杀配子效应的基因。目前所有的育种都是基于染色体的分类和染色体进行减数分裂重组的能力。确定杀配子效应的生物学基础将使替代系统能够更有效地被开发和部署在植物育种中。这最终将提高小麦的遗传多样性，特别是可用于小麦改良的野生种库。

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.