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。据预测，到本世纪末，全球气温将波动几度。拥有近10亿人口的小麦种植区将受到重大气温波动和相关减产的影响。小麦开花期间的较高温度可能会对随后的谷物产量产生重大影响。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不可预测。花发育期间的寒冷天气也与小麦产量的突然下降有关。20世纪80年代中期，花发育期间出现的寒冷潮湿天气导致严重不育，导致英国产量下降70%。在这种气候变化的背景下，小麦产量需要增加。显然，有可能筛选出那些表现出比小麦更耐高温的野生近缘小麦。然后，这些特征可以通过预育从野生相对小麦转移到小麦。然而，这种方法也存在问题。首先，研究表明，亲缘关系之所以更耐高温，仅仅是因为它们的基因组结构比小麦更简单，而不是因为它们一定携带着为它们提供更高耐温水平的基因。其次，在小麦的花发育过程中，有一些特定的阶段比其他阶段对温度效应更为敏感。小麦品种和野生近缘似乎也似乎更耐高温，仅仅是因为他们改变了减数分裂前和减数分裂阶段的时间，以避开极端温度。当然，这样的策略并不能缓解应对昼夜气温显著变化的问题。因此，开发其花发育阶段真正更耐温的小麦是一个重要的优先事项。要选择真正耐受温度的植物，需要在花发育的温度敏感阶段识别大量植物，然后将它们置于一定范围的温度下，然后才能评估随后对结实水平的影响。这种方法将非常耗时和费力。实际上，它需要在有限数量的植物上进行。我们的项目解决了这个问题。它将为选择更耐受花发育期间温度的小麦提供工具。我们的策略是基于这样一个事实，即我们最近的研究缩小了花发育的温度敏感阶段，涵盖了复制发生时的减数分裂前。先前的研究表明，5DL的长臂也带有一个基因座，为处于减数分裂前阶段的细胞提供了对低温的耐受性。我们最近的研究证实并推广了这些观察结果，即小麦染色体5D(5DL)的长臂携带一个座位LTP1，它为细胞提供了对低温(和高温)的耐受性，随后影响染色体配对的同源或同源。我们已经进行了初步的定位，并确定了5DL近端的基因座，其中包括PH1同源等位基因的位置。我们将改进图谱，以确定在减数分裂前控制低温耐受性的LTP1，并产生资源来表征5DLPH1同源等位基因。所产生的资源将用于评估这些基因座是否也控制着对高温的耐受性。LTP1的特性将为我们提供工具来筛选大量的小麦品种来鉴定那些具有不同变异的小麦品种。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体。

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.