BREAKTHRU: developing soil compaction resistant wheat

Significant improvements in crop yields are urgently required to meet the increase in world population by 2050. The ability of a crop to efficiently absorb water and nutrients relies on its root system to fully explore the available soil. However, soil can become too hard for roots to penetrate. This is referred to as soil compaction and represents a major challenge facing modern agriculture due to changes in how fields are managed and increasing weight of modern farming equipment. If crop roots are unable to penetrate soil due to compaction, this results in reduced yields of 25%, and up to 75% when combined with drought stress. Over half of Europe's farmed soil are prone to compaction, costing billions of pounds of losses. Despite its importance, little was known about why roots actually stop growing in hard soils. A series of (literally) ground-breaking experiments by our team (Pandey et al, 2021, Science) recently revealed that roots are able to penetrate highly compacted soil after disrupting their sensitivity to a plant hormone signal called ethylene.

The BREAKTHRU project proposes to exploit this new knowledge and re-engineer wheat to become resistant to hard soils by modifying their root responses to the signal ethylene. We will identify new wheat varieties whose roots are less sensitive to ethylene. Advanced imaging and artificial intelligence approaches will then be used to test whether the new wheat varieties we have selected are better able to grow in compacted soil and capture nutrients and water more readily. Finally, we will grow the most promising wheat lines in realistic field conditions including when soil has been compacted by farm machinery.

The knowledge gained from this study will provide vital new information about the key genes controlling root responses to soil compaction, helping breeders to design novel approaches to overcome soil compaction and enhance resource capture and yield in crops supporting efforts to improve food security in the UK.

Soil compaction represents a major challenge facing modern agriculture, reducing crop yields by up to 75% when combined with drought as roots struggle to penetrate hard soils, causing billions of pounds in losses annually. Efforts to mitigate the impacts of soil compaction include reducing tillage, controlled traffic farming (CTF) or sub-soil management. However, these approaches can be time consuming, costly to implement and ineffective for the deeper soil profile. Engineering crops to better withstand compacted soil environments offers a novel solution to improve crop growth in affected fields (Europe has 36-million-hectares of soil prone to compaction). This is now a realistic possibility after our recent discovery that roots can penetrate compacted soils after disrupting their sensitivity to the plant signal ethylene (Pandey et al. Science, 2021).

In this BBSRC project we propose to build on our recent findings and improve root responses to compacted soil in the most important UK crop wheat by modifying its ethylene response. Objective 1 describes how we will exploit natural allelic resources, induced (TILLING) and transgenic approaches to disrupt ethylene responses in either entire plants or selected root tissues. Objective 2 will use advanced phenomic and AI-based approaches to determine which ethylene insensitive wheat lines improve root and shoot growth in compacted soils. Objective 3 addresses whether ethylene insensitive wheat lines have improved performance and resilience for drought and nutrient capture under controlled conditions. A subset of the best performing wheat ethylene lines will then be tested under field conditions in Objective 4 to assess if our ethylene-based mechanism improves rooting across a range of UK soil management practices that cause compaction. The new knowledge generated promises to be transformative in laying the foundation for new crop varieties with improved root compaction traits.