Database Research Summaries2018 VIGS-enabled Interrogation of SB R Genes
Research Focus
The focus of this project is to identify the actual gene(s) within each of the multi-gene R/QRL loci.
Objectives
- Characterize the Rag5 gene conferring resistance to soybean aphids.
- Interrogate the Rps8 locus conferring resistance to the root rot pathogen P. sojae.
- Assess how the plant hormone auxin contributes to quantitative resistance to seedling pathogens.
- Develop a novel tool for selecting breeding progeny that harbor resistance genes.
Results
- Rag5: We have now harvested the Rag5-transgenic seed from two of the Rag5 lines and two control GFP lines. The transgenic seeds have been sowed during the October to December quarter of 2018. The seedlings are now been tested to verify the presence of the Rag5 transgene. Once these testing are complete, the positively transgenic plants will be subjected to feeding with soybean aphids to determine whether they indeed become resistant to the soybean aphids. Soybeans that are naturally susceptible to aphids; should become resistant if transformed with the correct Rag5 gene.
- Rps8: We have decided recently to use the PI line #399073 as the target plant for VIGS-enabled interrogation of Rps8 gene candidates. This is because the Rps8 gene was originally isolated in PI 399073; and it compared to the breeding lines that acquired the Rps8 gene from PI399073, the PI 399073 itself is substantially more responsible to ALSV VIGS. We are currently carrying out two parallel sets of experiments under this objective.
- QTLs on Chromosome 19: We are using two different approaches to attack the candidate genes mapped to the QTLs. We are assessing the candidate genes that potentially confer resistance to Fusarium graminearum in the seed coat. We are using ALSV VIGS to target the candidate genes CG1, CG2, CG3, CG4, and CG5 in the PI line #567301B resistant to F. graminearum. Our preliminary testing showed that we probably will succeed in silencing these genes in the seed coat, so that their expression would be diminished in the seed coat. The seed harvested from these plants will then be tested for loss of resistance to F. graminearum. In order to investigate a new gene found in the Conrad/Sloan population that was implicated in resistance to the root rot pathogen P. sojae, we used a hairy root procedure to successfully silence this gene, named as CG6. The resulting hairy roots are being assessed for changes in resistance to P. sojae.
Importance
- Full characterization will lead to its mobilization to more soybean varieties, resulting in improved soybean resistance to soybean aphid.
- An improved understanding facilitates more straightforward breeding of this valuable trait to other soybean varieties, reducing soybean losses caused by infections.
- Identification of genes within the two QRLs accelerates the adoption of these QRLs in elite soybean varieties, boosting soybean resistance to P. sojae in a more broad and long-lasting fashion. Although QRLs typically do not provide 100% protection, they target a broader category of pathogens (e.g. moreP. sojae pathotypes), and are harder to evade than single gene-mediated resistance.
- Success in developing a virus-based system expressing avr proteins will provide the seed industry with a faster and cost-effective tool for screening breeding progeny. This system will likely attract industry interest, providing licensing opportunities.
For more information about this research project, please visit the National Soybean Checkoff Research Database.
Funded in part by the soybean checkoff.
