Phenotyping root function in wheat

在英国，大约30%的小麦产量是在土壤上进行的，土壤水分不足会使产量（平均）减少1-2吨/公顷。这造成每年1.12亿至2.24亿英镑的产量损失（Foulkes等人，2001年）。包括有限范围的小麦品种的研究表明，具有深根系的基因型与水分有限环境中的高产相关，而具有浅根系的基因型与土壤水分充足时增加的养分吸收相关。然而，目前还没有全面的了解根系结构的配置导致提高产量，水分和养分利用效率的弹性，或什么权衡，如果有的话，有产量潜力。这是因为根隐藏在地下，只有通过艰苦的、破坏性的挖掘才能发现重要的特征。 该项目将开发一种利用电磁感应（EMI）的快速、非侵入性技术，以测量不同小麦品种地块不同深度的土壤干燥程度。目前的EMI技术可用于分析电导率随深度的变化，但不用于研究根系活动。该项目的一个关键目标是优化EMI的现有能力，以便它们可以用于表征不同小麦品种下的水分提取概况。我们将使用劳动密集型、侵入性和缓慢的电阻层析成像（ERT）作为工具，提供土壤干燥的高分辨率图像，以帮助优化快速、非接触和高效的EMI。 随着作物生长，土壤剖面的土壤水分提取模式与根系的生长和活动有关，将用EMI测量。这些数据将使用常规技术进行验证，例如通过土壤取芯进行根取样，埋置土壤水分探头，通过土壤强度计测量土壤强度的变化，以及根拉强度。最初的田间试验将包括20个英国精英小麦品系，其中一些品系在初步数据中显示出土壤水分提取模式的差异。我们将在田间试验中使用我们新的根系表型分析工具包与Avalon x Cadenza作图群体，该群体已经显示出营养吸收，产量和谷物品质的显着遗传变异。我们将确定我们的新工具包和小麦根QTL已经公布的QTL之间的对应关系。我们将使用不同深度的土壤干燥数据来测试假设，这些假设描述了干燥表层土壤中产量、深层水提取、土壤强度和根系位置之间的关系。这些信息对于育种者来说是必不可少的：例如，仅仅知道哪些品种可以产生更深的根是不够的;在对特定根系性状进行选择之前，还需要确认这样的根系在一系列环境中转化为更高的产量和产量稳定性。 在项目开始时，我们将建立一个由育种家和其他行业成员组成的项目咨询小组，以帮助指导调查材料的选择。该项目将提供一种全新的测量可能性，可应用于大型田间试验，以提供不同深度土壤水分随时间变化的空间图。在项目顾问小组的帮助下，我们将确定可用于测试我们新方法的现有田间试验。有许多实验室方法可用于对幼苗中的根进行表型分析，这些方法已经导致发现与各种根性状相关的QTL。然而，这是罕见的，任何这些QTL在田间条件下进行验证，因为目前的方法，检查在该领域的根是耗时和昂贵的。拟议中的研究将填补这一空白，并可能补充NIAB的BBSRC-LINK项目中关于小麦根系的工作。

In the UK, approximately 30% of the production of wheat is on soils where insufficient soil moisture decreases yields by (on average) 1-2 t/ha. This costs between £112M and £224M each year in lost production (Foulkes et al. 2001). Studies comprising a limited range of wheat cultivars have shown that genotypes with deep root systems have been associated with high yield in water limited environments, while those with shallow root systems have been associated with increased nutrient uptake when soil water is plentiful. However, there is no comprehensive understanding of what configuration of root system architecture leads to improved resilience of yields, water and nutrient use efficiency, or what the trade-offs, if any, there are with yield potential. This is because roots are hidden underground, and important traits are discovered only by laborious, destructive excavation of roots. This project will develop a rapid, non-invasive technique using electromagnetic inductance (EMI) to measure the degree of soil drying at different depths in plots of different wheat varieties. Current EMI technology can be used to profile with changes in conductance with depth, but is not being used to study root activity. A key objective for the project will be to optimise the existing capabilities of EMI, so that they can be used to characterize water extraction profiles beneath different varieties of wheat. We will use electrical resistance tomography (ERT), which is labour intensive, invasive and slow, as a tool to provide high resolution images of soil drying to help with the optimisation of EMI which is rapid, non-contact and efficient. Patterns of soil moisture extraction through the soil profile as the crop develops, which are related to growth and activity of the root system, will be measured with EMI. These data will be validated using conventional techniques such as root sampling via soil coring, buried soil moisture probes, changes in soil strength via penetrometer measurements, and root pulling strength. Initial field tests will comprise 20 UK élite wheat lines, some of which in preliminary data have shown differences in soil water extraction patterns. We will use our new root phenotyping tool kit in field trials with the Avalon x Cadenza mapping population, which has already shown significant genetic variation for nutrient uptake, yield and grain quality. We will determine the correspondence between QTLs identified with our new tool kit and wheat root QTLs already published. We will use soil drying data at various depths to test hypotheses that describe relationships between yield, deep water extraction, soil strength and root placement within drying superficial soil layers. This information is essential for the breeder: for instance, it is not enough to know which varieties can produce deeper roots; confirmation that such a root system translates to greater yield and yield stability across a range of environments is also required before any investment is made in selection for particular root traits. At the start of the project we will establish a project advisory panel comprising breeders and other members of industry to help guide the selection of materials for investigation. This project will provide a completely new measurement possibility that can be applied to large field trials to give a spatial map of soil water at different depths over time. With the help of the project advisory panel we will identify existing field trials that can be used to test our new methods. There are numerous laboratory methods available for phenotyping roots in seedlings that have led to the discovery of QTLs linked to various root traits. However, it is rare that any of these QTLs are validated under field conditions because current methods of examining roots in the field are time-consuming and expensive. The proposed studies will fill this gap, and can possibly complement work on wheat roots in the BBSRC-LINK project based at NIAB.