Capturing microbial co-symbiosis to sustain plant productivity

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As the world's environment changes it is essential that we produce crop plants adapted to these changes. Within soil, species of bacteria and fungi are involved in symbiotic relationships with the root and at the root-soil interface (so called rhizosphere of crops). The relationship allows each partner to benefit from mutual trading of resources such as critical growth-limiting nutrients. This is important since plants must acquire elemental nutrients such as nitrogen and phosphorus from their surrounding environment and the availability of these nutrients is often a major limitation to plant growth. As well as bringing nutritional enhancement, mutualistic interactions bring additional benefits to improve plant productivity, such as enhanced plant resistance to adverse environmental conditions or pathogen attack. However we cannot gain all of these benefits by simply adding many 'friendly' microbes to soil since the need of one microbe might cancel out the positive effect of another microbe on the plant. How the many rhizosphere microbes compete and combine to affect the plant is a complex question that needs to be studied at a detailed level.We have discovered that an important mutualistic fungus that helps protect plants against disease and supplies plants with phosphorus can also increase 'nodulation' in Medicago, a plant species that is a close relative of peas and beans. Nodulation is an interaction of nitrogen-fixing bacteria with plant roots that enables plants to gain otherwise unusable nitrogen. We will investigate how this enhancement of nodulation occurs, and determine if it still occurs for plants grown in different soil types. To do this we will use a range of state-of-the-art plant, soil and microbe analytical technologies to assess how microbes, plants and the soil type each contribute to the rhizosphere (microbial communities and soil adjacent to the root), and how this affects crop productivity in a range of soil types. New technologies for the identification of soil microbes mean that we are now at a point where we can study the effects of environments on multilateral interactions at the root rhizosphere - one of the most complex ecosystems on Earth. Together the results will help explain the enhanced-mutualistic effects that we have found. It will also help us to determine the importance of specific factors in the rhizosphere for agriculture, and how they could be enhanced to improve crop productivity in new environments.