Progress to understand the value of root traits for plant breeding has been slow due to challenges associated with phenotyping and the lack of known genes to target using molecular breeding approaches. To address this challenge and knowledge gap, our research has developed innovative phenotyping tools and contributed genetic breakthroughs that now provide new opportunities for imposing direct selection and manipulation of the below-ground components of wheat and barley.
Image: Shallow vs deep root system
In 2015, we developed the ‘clear pot’ root phenotyping method (Richard et al. 2015), which uses transparent pots and a smartphone for imaging. The cost-effective and high-throughput technique has transformed the ability to measure seminal roots traits in wheat. It has since been adopted in institutes and breeding programs around the world, including Mexico, Uruguay, Morocco, Algeria, Germany, England, and France. Its high-throughput nature has provided a gateway for QTL and gene discovery. We have applied the technique to discover QTL for root architecture in bread wheat (Richard et al. 2018), durum wheat (Alahmad et al. 2019), and barley (Robinson et al. 2016).
Our most renowned genetic breakthrough in cereal roots was the discovery that VRN1, a key gene in the flowering pathway, also modulates root system architecture in wheat and barley (Voss-Fels et al. 2018, Molecular Plant).
This was the first study to reveal the pleiotropic effects of flowering time loci on root development and, importantly, identified allelic variants that provide unique combinations of root and shoot architectures. The discovery was a result of significant collaboration with CSIRO and researchers in Germany. Since publication, a number of studies in other crops (e.g. common bean and maize) have also reported the involvement of flowering time loci in modulating root architecture. Thus, the VRN1 breakthrough created a new focus for crop researchers aiming to uncouple above- and below-ground development.
Most recently, Hickey Lab developed an innovative ‘toolkit’ to rapidly modify root systems through single plant selection (Rambla et al. 2021 Plant Methods). Using this approach, we developed elite wheat lines with modified root traits, which were evaluated for the first time in the field in 2021 using a combination of above- (UAV) and below-ground (root coring) phenotyping techniques to validate changes to the root system and investigate root-shoot relationships.