Extended: Evaluation of root system architecture diversity in field pennycress (Thlaspi arvense L.) and genetic dissection using genome-wide association mapping studies

The root system is the interface between the plant and the soil and is central to plant resource capture. Field pennycress (Thlaspi arvense L.) is a diploid annual that has the potential utility as a cover crop for reducing soil erosion and nutrient losses; and as a cash crop with rich oil seeds amenable as a biofuel (30-35% oil) or high-protein animal feed. The objective of this study was to (1) precisely characterise root system architecture diversity in pennycress, (2) uncover the molecular basis of root trait diversity in pennycress using genome-wide association studies (GWAS), and to (3) understand how root trait diversity can affects plant and ecosystem performance. A field trial was conducted for 354 sequenced pennycress accessions and a subset of these accessions were also grown in a mesocosm system as a controlled field plot in the greenhouse. Root and shoot traits were evaluated and 15N tracer uptake measurements were collected from greenhouse studies. Significant root trait diversity was observed among the panel with a positive correlation between root size to 15N tracer uptake. Both plant- and canopy-specific traits are being evaluated to assess how these traits contribute to performance as individuals and as a stand. Fine-mapping of quantitative root traits collected from the field has revealed significant marker–trait associations. As pennycress is highly amenable for CRISPR/Cas9 genome editing, knock-out mutants are being generated for root trait genes identified through GWAS. Together, through harnessing these diverse root phenotypes and genetic engineering it may be possible to enhance pennycress climate adaptation, enhance yield as a cash crop, and provide greater ecosystem function as a cover crop.