The Stupar research group has recently developed a system that can either add a new gene to the genome (standard transformation) or reliably generate targeted DNA changes for specific genes (using a CRISPR/Cas9 system )(Michno et al. 2015; Liu et al. 2019). For the proposed project, both of these methods will be used to create new traits in soybean plants for genes involved in IDC tolerance and plant architecture. A list summarizing the target genes for this project is shown below:

1. IDC genes: We have used genetics and genomics to identify a leading candidate gene for IDC tolerance on soybean chromosome 5. We are testing the actions of this gene by changing its function in transient hairy root tissues. We will overexpress the gene and measure iron content in these cells. We will also mutate this gene in ‘Bert’ using gene editing techniques at UMN and phenotype the resulting plant in IDC conditions in subsequent generations. Identification of this gene will lead to new insight into IDC mechanisms in soybean and lead to new genetic and/or management strategies that target the functions of these pathways.

2. Architecture genes: We have made significant progress on using gene editing to mutate a candidate architecture gene known as Lps1. In this funding cycle, we will identify the mutants and evaluate their phenotype to see if they show the hypothesized changes in plant branch angle. Additionally, numerous genes have been identified in other plant species that regulate shoot architecture. Genes that exhibit a large effect and appear to be conserved across plants are the LATERAL SUPPRESSOR (LAS) and TEOSINTE BRANCHED1 (TB1) genes, and the MORE AXILLARY GROWTH (MAX) gene family. We plan to examine the function of these genes in soybean. This information will be used to identify a stronger architecture type that informs molecular breeding efforts for more robust soybean varieties.

To map the branch orientation trait, we will order advanced inbred lines that are polymorphic for this trait. We will use identify molecular markers that segregate with the respective orientation types (spiral or flat). We will identify nearly identical siblings that vary for these markers and establish near isogenic lines (NILs) from the progeny of the siblings, which will allow us to compare the effect of this trait on harvestable yield. We will fine-map this locus by tracking molecular markers that segregate with the respective spiral and flat branching orientations. From this, molecular markers that segregate with the trait will be identified for breeders to use.