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

点击翻译按钮获取中文摘要

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.