PUSHING THROUGH HARD TIMES: uncovering how roots sense soil compaction

Food security represents a major global issue. Topsoil, the most precious "natural capital assets", provides nearly 95% of food. The sense of urgency over topsoil is growing as the population is projected to reach 9 billion by 2050. Compaction hampers soil's ability to filter water, absorb carbon and retain water and nutrient to support the crop plants. The ability of a crop to efficiently absorb water and nutrients relies on its root system to fully explore soil available.

Use of heavy farming equipment, intensity of farm traffic and overgrazing lead to soil compaction. For example, the average weight of vehicles used on farms has approximately tripled since 1966 and maximum wheel loads have risen by a factor of six. Soil compaction can reduce crop yields by as much as 60%. Therefore, developing compaction resistant crops is of paramount importance. Despite its increasing global agronomic importance, little is known about how crop roots may respond to soil compaction.

My BBSRC Discovery Fellowship investigates how crop roots respond to soil compaction and then use this knowledge to develop crops with improved penetration ability. My project initially attempts to 'fill in the gaps' between roots sensing soil compaction and then altering their growth and shape of their root tips. To help my studies, I have already identified plant signals and genes such as ethylene and EIN2 that are important for this process. Several promising approaches will also be conducted including modifying roots to be less sensitive to ethylene.

The knowledge gained from my fellowship will provide new information about the key genes and processes controlling root responses to soil compaction, helping breeders design novel approaches to manipulate root growth to enhance resource capture and yield in crops. Developing future crops resistant to soil compaction can help their roots forage deeper for water to help mitigate drought stress (hard soil which is tough to penetrate), reduce flooding (compacted soil poses increased risk of flooding by restricting the water absorption from the surface), nitrogen stress (as this nutrient leach deeper in soil) and also capture more carbon in the soil.

My fellowship project will be undertaken in Plant Sciences at the University of Nottingham. The University hosts a world leading multidisciplinary team of researchers composed of experts from Maths, Plant, Crop, Soil and Computer Sciences, all dedicated to 'uncover' the hidden half of plants. To achieve this, these researchers have created the Hounsfield Facility which hosts state-of-the-art microCT scanners and other advanced imaging platforms.

I will also benefit from the unparalleled support of my host Prof. Malcolm Bennett and colleagues Soil Scientist Prof. Sacha Mooney and Crop Scientists Dr. Sean Mayes, Dr. Rahul Bhosale and Dr. Darren Wells. My project also involves international and UK collaborators which include experts in Sweden (Prof. Karin Ljung for hormone analysis), China (Prof. Dabing Zhang providing rice resources and expertise) and Rothamsted Research (Dr. Steve Thomas and Dr. Richard Whalley, wheat genetics and soil compaction expertise).

Soil compaction represents a major challenge facing modern agriculture due to changing tillage practices and increased weight of modern farming equipment. When soil strength becomes excessive crop roots are unable to penetrate soil due to mechanical impedance. Despite its importance, there is a significant knowledge gap concerning how crop roots overcome soil compaction. I recently discovered that the gaseous hormone signal ethylene regulates root responses to mechanical impedance in crops after I demonstrated rice roots of ethylene response mutants can penetrate highly compacted soil, in stark contrast to wild type plants.

My BBSRC Discovery fellowship aims to discover how ethylene controls compaction responses in crop roots and then exploit this knowledge to engineer novel compaction resistant cereal crops. To achieve these ambitious goals, I will address 3 key objectives. Objective 1 will determine if reduced diffusion of the gaseous signal ethylene acts as a regulatory mechanism to trigger root adaptive growth changes in compacted soil environments.

Objective 2 will pinpoint the key downstream signals and genes underpinning root-soil compaction responses and later functionally validate promising candidate genes to manipulate root penetration traits in cereal crops.

Objective 3 will validate ethylene regulates wheat root soil compaction responses and then deliver high throughput phenotypic screens, germplasm and markers to accelerate breeding efforts to select compaction resistant wheat lines.

My BBSRC Discovery fellowship project is very timely, novel and employs cutting-edge interdisciplinary tools and technologies available and/or developed at the host Institute that includes state-of-art tomographic imaging, deep learning and genomic resources that I will exploit to address this major global agronomic problem.