Update:
The key activities undertaken in this project focused on characterizing genes involved in Peking-type SCN resistance to elucidate their mechanism of action and identify the most effective combination of genes for use in elite germplasm to enhance durability of resistance. We made substantial progress towards determining how Rhg1 and Rhg4 function in soybean Peking-type resistance to SCN by further characterization of Rhg1 and Rhg4 gene function. We show that the SNAP protein at the rhg1 locus is required and sufficient for Peking-type SCN resistance in combination with Rhg4. We provide compelling genetic evidence that Peking-type rhg1 resistance in cv Forrest is fully dependent on the Rhg4 gene and demonstrate that this resistance is mechanistically different from the PI 88788-type of resistance that only requires rhg1. We identified specific soybean root proteins that directly interact with Rhg1 and Rhg4 to mediate resistance. We also made significant progress towards establishing a gene model for Peking-type resistance to SCN by conducting forward screening of developed soybean mutant populations to identify genes involved in SCN resistance and identifying and analyzing potential genes that interact with the Rhg1 and Rhg4 genes using bioinformatics, TILLING and mutant analysis. Lastly, we collaborated with the USB Soybean Tissue Culture & Genetic Engineering Center (Dr. Wayne Parrott) to transfer SCN resistance genes into elite germplasm and are continuing to work with Center scientists to deliver identified SCN resistance genes into different genetic backgrounds and test for increased efficacy/durability of resistance.
Did this project meet the intended Key Performance Indicators (KPIs)? List each KPI and describe progress made (or not made) toward addressing it, including metrics where appropriate.
KPI 1: Soybean proteins that interact with the Rhg1 and Rhg4 proteins are determined and confirmed to play a role in SCN resistance. These findings are shared with and adopted by soybean breeders.
>> Co-immunoprecipitation assays have identified potential Rhg1 and Rhg4 interacting proteins, including a potential Rhg1-Rhg4 interaction, and are being analyzed to decipher the mechanisms by which these interactions trigger the resistance mechanism to SCN. The results have been shared with soybean breeders and this knowledge has been adopted for more efficient development of varieties with Peking-type resistance.
KPI 2: Transgenic soybeans with different combinations of resistance loci are developed and the effect on the resistance phenotype is measured. These are made available to public and private soybean breeders.
>> We developed and demonstrated for the first time the functionality of a SCN resistance gene (Rhg4) in a transgenic soybean plant. With our new knowledge of how Peking-type resistance is working, multiple dual constructs carrying both Rhg1 and Rhg4 (derived from Forrest) have been designed and transformed into different genetic backgrounds for testing. This may offer a means to more quickly develop Peking-type resistance in high yielding varieties with other valued traits.
KPI 3: Effective breeding strategies for durable SCN resistance in soybean are developed and are utilized by public and private soybean breeders worldwide.
>>We initiated the development of several EMS mutagenized soybean populations with resistance to SCN. These populations are being used to decipher SCN resistance and provide new germplasm for SCN breeding with no yield penalty.
Expected Outputs/Deliverables - List each deliverable identified in the project, indicate whether or not it was supplied and if not supplied, please provide an explanation as to why.
1. A better understanding of how SCN resistance genes function to confer resistance to SCN – SUPPLIED, ADDITIONAL ANALYSIS UNDERWAY
2. Developed approaches to breed for more durable resistance in soybean – SUPPLIED, ADDITIONAL ANALYSIS UNDERWAY
3. Whole soybean transgenic lines with various gene combinations evaluated for resistance to SCN – SUPPLIED, ADDITIONAL ANALYSIS UNDERWAY
4. Identification of potential new genes for resistance to SCN – SUPPLIED, ADDITIONAL ANALYSIS UNDERWAY
Describe any unforeseen events or circumstances that may have affected project timeline, costs, or deliverables (if applicable.)
Project was terminated at the end of the first year of a proposed three year project.
What, if any, follow-up steps are required to capture benefits for all US soybean farmers? Describe in a few sentences how the results of this project will be or should be used.
The knowledge gained will be exploited to improve soybean cultivars for disease resistance by accelerating breeding programs, strategically deploy resistance for enhanced durability, and contribute required knowledge for engineering existing elite soybean cultivars for SCN resistance.
List any relevant performance metrics not captured in KPI’s.
Peer-reviewed publications reporting the results of this work:
Rhg1
The soybean GmSNAP18 gene underlies two types of resistance to soybean cyst nematode (2017) Shiming Liu, Pramod K. Kandoth, Naoufal Lakhssassi, Jingwen Kang, Vincent Colantonio, Robert Heinz, Greg Yeckel, Zhou Zhou , Sadia Bekal, Johannes Dapprich, Bjorn Rotter, Silvia Cianzio, Melissa G. Mitchum & Khalid Meksem. Nature Communications | 8:14822 | DOI: 10.1038/ncomms14822
Characterization of the Soluble NSF Attachment Protein gene family identifies two members involved in additive resistance to a plant pathogen (2017) Naoufal Lakhssassi, Shiming Liu,*, Sadia Bekal,*, Zhou Zhou, Vincent Colantonio, Kris Lambert, Abdelali Barakat & Khalid Meksem. Scientific Reports | 7:45226 | DOI: 10.1038/srep45226
Rhg4
Systematic mutagenesis of serine hydroxymethyltransferase reveals an essential role in nematode resistance (2017) Pramod K. Kandoth, Shiming Liu, Elizabeth Prenger, Andrew Ludwig, Naoufal Lakhssassi, Robert Heinz, Zhou Zhou, Amanda Howland, Joshua Gunther, Samantha Warren, Andi Dhroso, Peter LaFayette, Donna Tucker, Sarah Johnson, James Anderson, Alaa Alaswad, Silvia R. Cianzio, Wayne A. Parrott, Dmitry Korkin, Khalid Meksem, & Melissa G. Mitchum. Plant Physiology | 175:1370-1380
SCN resistance is known to be mediated by multiple genes/clusters of genes. Recent work, including that described here, has shed light on how the products of known resistance genes actually function to confer SCN resistance to the soybean plant. The researchers have added to the knowledge of the 2 primary SCN resistance genes, Rhg1 and Rhg4, but also identified alternative alleles and potential sources of resistance outside of these two genes for future analysis.