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

植物有不同的能力来改造土壤，使其更稳定和多产的想法并不新鲜。一些更引人注目的证据来自大沙尘暴等环境灾难，在那里，从草原草到单一种植玉米的过渡直接导致了毁灭性的土壤侵蚀。根就像土壤中的钢筋，分泌出聚合土壤的化合物，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，增加它们渗透的距离，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已经发现，具有几乎相同基因组成的作物群体在多毛和渗出方面存在很大差异。对于植物育种家来说，这些发现是令人兴奋的，因为它们表明有能力根据对土壤有很大影响的根系性状选择作物。通过在根表面对土壤进行工程改造，作物吸收更多的养分，并且还增强了对作物的水和气体的运输和储存。这意味着作物将能够更有效地捕获和储存养分，并创造一个更能抵御干旱或洪涝等天气引起的压力的环境。在寻找应对粮食安全挑战的作物方面，这种尚未开发的通过根系性状改善土壤物理操纵的潜力提供了相当大的潜力。该项目将探索各种根系性状如何改变土壤的物理性质，以提高作物捕获水分和养分的效率。最终的产出将是数据和数值模型，这将有助于植物育种者确定更可持续农业生产的最佳根系性状。我们首先从一系列作物中收集根系分泌物，并将它们以特定浓度添加到不同的土壤中。渗出物和渗出物：土壤混合物的物理测试将提供关于根系如何改变土壤的水动力学和机械稳定性的新信息。这些信息被用来适应医学生物学和土壤力学的模型，以开始描述土壤如何在植物根部的界面形成。接下来，我们用生长在土壤中的植物进行测试。我们将测量不同的根性状（毛和渗出）如何改变水动力学（存储，运输和疏水性）使用小规模的探针，并提取土壤，以测量其机械性能是如何受到影响。X射线成像将测量土壤结构如何随着根系生长和土壤干湿变化而变化。沿着根系的长度，由于年龄的不同，影响也不同。根毛生长，死亡，然后降解，所以我们将测量从茎基部到根尖的根-土界面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，我们把作物在温室和田间成熟。这与HGCA关于土壤管理的项目相联系，我们使用了10多年来不同形式土壤耕作的地块。随着越来越多的可耕地农民转向减少投入的耕作系统，田间资源使我们能够探索在用于植物育种的传统条件下（犁至20 cm）与浅耕相比，根系性状的反应。这将我们最初的实验室研究带入该领域，从而可以验证项目中开发的数值模型。因此，我们将探讨土壤是如何操纵的植物在根-土界面和特定的根性状的影响，以提高资源捕获。植物育种者将能够利用这些信息来确定有利的根系性状，以寻找更可持续的作物品种。我们还将提高对土壤结构的理解，并影响碳和水的动态。

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.