Loss of soil organic matter content and soil macroaggregates (crumbs) as a result of arable cultivation reduces soil water and nutrient holding capacity and are major global constraints on crop yields and efficient use of fertilizer. In the UK wheat yield have not increased over nearly 20 years due to interactions between genetic, environment and management constraints. Modern wheat breeding has focussed on selection for disease resistance and increasing yield and quality of the grain, without consideration of other traits that can influence soil quality and ultimately, the long-term sustainabilty of soil. Soil erosion is a major global problem exacerbated by ploughing, loss of soil organic matter and the macroaggregates that hold soil together against water and wind erosion.
One of the most important functional groups of organisms that are involved in stabilizing soil macroaggregates and contributing to soil organic matter storage are symbiotic fungi called mycorrhizas that receive sugars from plant roots in return for providing nutrients and water to the plants. We have recently shown that some modern wheat varieties have limited or no ability to form mycorrhizal symbiosis, and members of our consortium were amongst the first to show that conventional arable farming reduces the diversity and functioning of these symbionts. Loss of these symbionts and their functioning is thought to be contributory to loss of soil quality, both directly through effects on soil organic matter and soil structure, and indirectly though reductions in defences against pathogens which are induced by the symbiosis and plant growth promoting rhizobacteria that are thought to act synergistically with mycorrhizas.
MycoRhizaSoil will determine the crucial roles mycorrhiza and co-associated soil microorganisms play in maintaining soil structure and organic matter content, which are required for high yields, and directly addresses for the first time the benefits of selecting wheat genotypes and less intensive management to enhance the functional benefits of these crop-microbe interactions to deliver lower input, more sustainable and resilient wheat production.
Our approach combines laboratory and field based research using wheat lines that differ in mycorrhiza-forming capacity but are otherwise genetically very similar, selected over 500 lines of wheat bred from two parents that differed in mycorrhiza-forming ability. The laboratory-based research will resolve the mechanistic basis of mycorrhiza-induced systemic defenses to important root and shoot pathogens that cause major yield losses of wheat in the UK and globally. In a series of sequential field trials using the selected wheat lines we will determine the extent to which artificial inoculation with mycorrhizal fungi, the temporary conversion of crop land to grassland (to restore mycorrhiza) and adoption of no-tillage leads to improvements in soil quality and crop resilence to drought, excess water and native diseases compared to wheat grown conventionally with annual tillage. Our agenda-setting research programme identifies a new set of targets for optimising plant breeding and arable management for sustainable wheat production.
Our ambitious ultimate goal is to provide the scientific evidence to evaluate the benefits of simultaneously reducing the need for ploughing (one of the most fossil-fuel demanding farm operations and one of the most damaging to soil conservation and sustainability) and increasing the activities of beneficial soil microorganisms through wheat genotype selection. In combination we predict these approaches will increase the storage of soil organic carbon in the surface soil, help restore water-stable macroaggregates and increase crop resilience to climate stress (too much and too little water) and diseases.