Characterisation of the low temperature tolerant locus (Ltp1) on wheat chromosome 5D

未来50年，小麦产量需要增加60%。然而，这种增长需要在气候变化的背景下发生。预计到本世纪末，全球气温将波动几度。近10亿人口的小麦种植区将受到气温大幅波动和相关减产的影响。小麦开花期间的高温会对随后的粮食产量产生重大影响。随着包括英国在内的其他地区出现更多极端天气，气候也将变得越来越难以预测。花发育期间的寒冷天气也与小麦产量的突然下降有关。在20世纪80年代中期，在花卉发育期间发生的寒冷潮湿天气导致了严重的不育，导致英国产量减少了70%。在这种气候变化的背景下，小麦产量需要增加。很明显，筛选小麦的野生近缘品种，找出比小麦更耐温的品种是可能的。这样的性状可以通过预育种从野生亲缘种转移到小麦上。然而，这种方法存在一些问题。首先，研究表明，近亲小麦对温度的耐受性更强，仅仅是因为它们的基因组结构比小麦更简单，而不是因为它们携带的基因使它们具有更高的耐温性。其次，小麦花发育的某些阶段对温度的影响比其他阶段更敏感。小麦品种和野生近缘种似乎也更耐温，仅仅是因为它们改变了减数分裂前和减数分裂阶段的时间，以避免极端的温度。当然，这种策略并不能缓解处理昼夜温度显著变化的问题。因此，培育出真正耐温的花发育阶段的小麦是当务之急。选择真正耐受温度的植物需要鉴定大量处于花发育温度敏感阶段的植物，然后将它们置于一定温度范围内，然后对结实率的后续影响进行评分。这种方法将非常耗时和费力。实际上，它需要在有限数量的工厂上执行。我们的项目解决了这个问题。这将为选择在花发育过程中对温度更耐受的小麦提供工具。我们的策略是基于这样一个事实，即我们最近的研究已经缩小了花发育的温度敏感阶段，包括复制发生时的减数分裂前。先前的研究表明，5DL的长臂也携带一个基因座，该基因座为减数分裂前阶段的细胞提供低温耐受性。我们最近的研究证实并扩展了这些观察结果，即小麦染色体5D （5DL）的长臂携带一个位点Ltp1，它在这一阶段为细胞提供对低温（和高温）的耐受性，随后影响染色体是否同源或同源配对。我们已经进行了初步的定位，并将位点定义为5DL的近端区域，其中包括Ph1等位基因的位置。我们将对该图谱进行细化，以确定Ltp1在减数分裂前控制低温耐受性，并生成资源来表征5DL Ph1同等位基因。所产生的资源将用于评估这些基因座是否也控制对高温的耐受性。Ltp1的特征将为我们提供筛选大量小麦品种的工具，以识别具有不同位点变异的小麦品种。可以对这些植物的耐温水平进行评估，以确定为植物提供最高耐温水平的变异。

Wheat production will need to increase by 60% in the next 50 years. However, this increase will need to happen against a background of climatic change. Temperatures are predicted to fluctuate globally by several degrees by the end of this century. The wheat growing area of nearly one billion people will be affected by major temperature fluctuations and an associated reduction in yield. Higher temperatures during wheat's flowering can have a major effect on subsequent grain yield. The climate is also going to become increasingly unpredictable with more extremes of weather in other regions, including the UK. Cold weather during floral development is also associated with sudden reductions in wheat yields. Cold wet weather occurring during floral development during mid-1980s resulted in significant sterility, leading to a 70% reduction in yields in the UK. Wheat yields need to increase against this background of climate change. Clearly it is possible to screen wild relatives of wheat for those exhibiting greater temperature tolerance than wheat. Such characters can then be transferred from the wild relative to wheat through prebreeding. However, there are problems with this approach. Firstly, studies have shown that the relatives are more tolerant of temperature simply because their genome structure is simpler than wheat, not because they necessarily carry genes which provide them with a higher level of temperature tolerance. Secondly, there are particular stages in wheat's floral development that are more sensitive to temperature effects than others. Wheat varieties and wild relatives may also seem apparently more temperature tolerant simply because they have altered the timing of their pre-meiotic and meiotic stages, to avoid the extremes of temperature. Of course, such a strategy does not alleviate the problem of dealing with marked changes in temperatures during day and night. Thus, developing wheat whose floral development stages are truly more tolerant of temperatures is an important priority. Selection of plants truly tolerant of temperatures would require the identification of large numbers of plants at the temperature sensitive stage of floral development, then subjecting them to a range of temperatures, before scoring the subsequent effect on the level of seed set. This approach would be hugely time consuming and laborious. Realistically, it needs to be performed on a limited number of plants. Our project addresses this problem. It will provide tools for selecting wheat that is more tolerant of temperatures during floral development. Our strategy is based around the fact that our recent research has narrowed down a temperature sensitivity stage of floral development covering pre-meiosis when replication occurs. Previous research showed that the long arm of 5DL also carries a locus which provides cells at this pre-meiotic stage with a tolerance to low temperatures. Our recent studies confirmed and extended these observations, namely that the long arm of wheat chromosome 5D (5DL) carries a locus, Ltp1 which provides cells at this stage with a tolerance to low (and high) temperatures, subsequently affecting whether chromosomes pair homologously or homoeologously. We have undertaken preliminary mapping and have defined the locus to the proximal region of 5DL, which includes the location of the Ph1 homoeoallele. We will refine the mapping to identify Ltp1 controlling low temperature tolerance during pre-meiosis, and generate resources to characterise the 5DL Ph1 homoeoallele. The resources generated will be used to assess whether these loci are also controlling tolerance to high temperature. The characterisation of Ltp1 will provide us with tools for screening a large number of wheat varieties to identify those with different variants of the locus. Such plants can be assessed for level of their temperature tolerance, to identify the variant providing the plant with the highest level of temperature tolerance.