Rhizosphere by design: breeding to select root traits that physically manipulate soil

植物有不同的改造土壤的能力，以使它们更稳定和更高产，这一想法并不新鲜。一些更具戏剧性的证据来自环境灾难，如大沙尘暴，从草原草到单一种植玉米的转变直接导致了毁灭性的土壤侵蚀。根在土壤中的作用就像加固棒，会释放出化合物，使土壤凝聚在一起，增加水分储存，帮助释放养分。根的表面也可以有毛发状的结构，这增加了它们穿透的距离，从而与土壤相互作用。因此，植物改造土壤的能力对它们自己的生产力有很大的好处。现代植物生物技术研究发现，基因构成几乎相同的作物群体的毛发和分泌物存在很大差异。对于植物育种者来说，这些发现是令人兴奋的，因为它们表明了一种选择作物根部特征的能力，这将对土壤产生重大影响。通过在根表改造土壤，作物吸收了更多的养分，水分和气体向作物的运输和储存也得到了加强。这意味着农作物将能够更有效地获取和储存养分，并创造出对干旱或内涝等天气压力更具弹性的环境。在寻找应对粮食安全挑战的作物方面，这种尚未开发的潜力在通过根系特征改善土壤物理操纵方面提供了相当大的潜力。该项目将探索不同的根系特征如何改变土壤的物理性质，以提高作物吸收水分和养分的效率。最终的输出将是数据和数字模型，这些数据和数字模型将帮助植物育种者确定更可持续的农业生产的最佳根系特征。我们首先收集一系列作物的根分泌物，然后以特定的浓度将它们重新添加到不同的土壤中。渗出物和渗出物的物理测试：土壤混合物将提供有关根部如何改变土壤的水动力和机械稳定性的新信息。这些信息被用来调整医学生物学和土力学的模型，以开始描述土壤如何在与植物根的交界处形成。接下来，我们将对种植在土壤中的植物进行测试。我们将使用小型探测器测量不同的根系特征(多毛和分泌物)如何改变水动力学(储存、运输和疏水性)，并提取土壤以测量其力学性质如何受到影响。X射线成像将测量土壤结构随着根的生长和土壤的潮湿和干燥而发生的变化。根部长度的影响因年龄的不同而不同。根毛生长、死亡，然后降解，所以我们将测量从茎的根基到根尖的根-土壤界面上的机械和水文行为的变化，以获得了解整个根系所需的信息。最后，我们在温室和大田里让庄稼成熟。这与HGCA关于土壤管理的项目相联系，在该项目中，我们使用经过10多年不同形式土壤耕作的地块。随着越来越多的耕地农民转向减少投入的耕作制度，田地资源让我们探索在用于植物育种的传统条件下(耕作至20厘米)与浅得多的耕作相比，根系特征如何反应。这将我们最初的实验室研究带入该领域，使该项目中开发的数值模型得以验证。因此，我们将探索植物如何在根-土壤界面操纵土壤，以及特定的根系特征对提高资源捕获的影响。植物育种者将能够利用这些信息来确定有利的根部特征，以寻找更可持续的作物品种。我们还将提高对土壤形态结构及其对碳和水动态的影响的理解。

The idea that plants have differing abilities to engineer soil to make them more stable and productive is not new. Some of the more dramatic evidence comes from environmental disasters like the Great Dust Bowl, where the transition from prairie grasses to monoculture maize led directly to devastating soil erosion. Roots act like reinforcing rods in soil and exude compounds that aggregate soils, increase water storage and help release nutrients. Roots can also have hair-like structures on their surface that increase how far they penetrate and therefore interact with soils. The ability of a plant to engineer soil therefore has significant benefits to their own productivity. Modern plant biotechnology research has identified large variations in the hairiness and exudation of populations of crops that have nearly identical genetic makeup. For plant breeders these findings are exciting, as they suggest an ability to select crops for root traits that will have a large impact on soils. By engineering the soil at the root surface, the crop takes up more nutrients, and the transport and storage of water and gases to the crop is also enhanced. This means that crops will be able to capture and store nutrients more efficiently, as well as produce an environment more resilient to weather induced stresses, such as drought or water-logging. In the search for crops to address food security challenges, this untapped potential in improving the physical manipulation of soils by root traits offers considerable potential. This project will explore how various root traits change the physical properties of soil to improve the efficiency with which crops can capture water and nutrients. The ultimate outputs will be data and numerical models that will help plant breeders identify optimal root traits for more sustainable agricultural production. We start by collecting root exudates from a range of crops and adding them back to different soils at specific concentrations. Physical testing of the exudates and of exudate:soil mixes will provide new information on how roots may change water dynamics and mechanical stability of soils. This information is used to adapt models from medical biology and soil mechanics to begin to describe how soils form at the interface with plant roots. Next we move to tests with plants grown in soil. We will measure how different root traits (hairiness and exudation) change water dynamics (storage, transport and hydrophobicity) using small scale probes, and extract soils to measure how its mechanical properties are affected. X-Ray imaging will measure how the soil structure changes as roots grow and soils wet and dry. Along the length of the root the effects are different due to age. Root hairs grow, die and then degrade, so we will measure changes in the mechanical and hydrological behaviour at the root-soil interface from the base of the stem to root tips to get information need to understand whole root systems. Finally we take crops to maturity in the glasshouse and field. This links into an HGCA project on soil management where we use plots that have been under different forms of soil cultivation for over 10 years. As an increasing proportion of arable farmers switch to reduced input tillage systems, the field resource lets us explore how the root traits respond under traditional conditions used for plant breeding (ploughing to 20 cm) versus much shallower cultivation. This takes our initial laboratory research into the field, allowing verification of numerical models developed in the project. We will hence explore how soils are manipulated by plants at the root-soil interface and the impact of specific root traits for improving resource capture . Plant breeders will be able to use this information to identify favourable root traits to target in the search for more sustainable crop varieties. We will also improve the understanding of the structure of soil forms and influences carbon and water dynamics.