Root Phenotyping in the Field: The Use of X-ray Computed Tomography in Field Structured Soils.

It has now been recognised that understanding root traits which confer more effective use of resources represents a missed opportunity in breeding for more resilient crops (Richards et al., 2012). Roots are inherently difficult to assess in an agricultural setting and as a consequence breeders have largely ignored the contribution of roots to productivity (Lynch, 1995). A detailed understanding of roots and their immediate soil environment is a primary factor determining the availability of resources and is extrinsically linked to plant productivity (Moran et al., 2000). Yet, our understanding of how roots interact with the soil, especially at the micro-scale level, remains limited (Perret et al., 2007). Common techniques involve destructive analysis of RSA (root system architecture) result in the loss of key information (elongation rates and root angles) as well as important soil characteristics e.g. 3D pore connectivity (Mancuso, 2011). Direct visualisation of root:soil interactions has been impossible due to roots growing in opaque soil, but this is possible through the use of the technique X-ray Computed Tomography (CT). X-ray CT is a 3D non-destructive technique that can be repeatedly undertaken on the same soil core; allowing soil structure, porous architecture and root system architecture to be simultaneously visualised and quantified at scales relevant to root:soil interactions (µm). X-ray CT is used throughout the soil and plant sciences, such examples include using the technique to visualise and quantify soil structure (Mooney et al., 2012), investigating the impacts of soil compaction on growing roots (Tracy et al., 2012) and water filled pores (Tracy et al., 2015). The use of X-ray CT to directly visualise root:soil interactions in field structured soil and the impact of soil management and cultivation practice on root phenotypes and their ability to cope with stresses will be presented.