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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #429320
Research Project: Leveraging Crop Genetic Diversity and Genomics to Improve Biotic and Abiotic Stress Tolerance in Soybean

Location: Corn Insects and Crop Genetics Research

Title: Rpp2 encodes a TIR-NBS-WH-LRR protein that confers resistance to Phakopsora pachyrhizi in soybean

Author
item Holan, Katerina
item THUNES, NICOLE - Oak Ridge Institute For Science And Education (ORISE)
item Lincoln, Lori
item Wright, Amy
item DIERS, BRIAN - University Of Illinois
item ABDELNOOR, RICARDO - Embrapa
item O'Rourke, Jamie
item Whitham, Steven
item Pedley, Kerry
item Graham, Michelle

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2026
Publication Date: 4/2/2026
Citation: Holan, K.L., Thunes, N.C., Lincoln, L.M., Wright, A.L., Diers, B., Abdelnoor, R.V., O'Rourke, J.A., Whitham, S.A., Pedley, K.F., Graham, M.A. 2026. Rpp2 encodes a TIR-NBS-WH-LRR protein that confers resistance to Phakopsora pachyrhizi in soybean. Molecular Plant-Microbe Interactions. https://doi.org/10.1094/MPMI-02-26-0013-R.
DOI: https://doi.org/10.1094/MPMI-02-26-0013-R

Interpretive Summary: Soybean rust, caused by the fungus Phakopsora pachyrhizi, is one of the most formidable pathogens of soybean. It is established in all major soybean growing areas of the world and presents a significant impediment to global soybean production. Severe infection reduces photosynthesis, resulting in premature defoliation, reduced seed quality and reduced crop yield. ARS scientists in Ames, Iowa, and Fort Detrick, Maryland, collaborated with university scientists to sequence the region of the genome containing Resistance to Phakopsora pachyrhizi 2 (Rpp2), identifying 14 candidate resistance genes. Knocking down the activity of these genes resulted in loss of resistance to soybean rust. Of the 14 genes, only one was activated in response to soybean rust infection, making it the sole candidate for Rpp2. Breeders can use this information to stack soybean rust resistance genes into elite soybean cultivars to defend against pathogen attack. This research will benefit farmers, growers and the American public.

Technical Abstract: The obligate biotrophic fungus Phakopsora pachyrhizi Syd. & P. Syd., the causal agent of soybean rust, is among the most formidable pathogens of soybean (Glycine max [L.] Merr.). The pathogen is now established in all major soybean growing areas of the world and presents a significant impediment to global soybean production. Most soybean germplasm is susceptible, enabling the fungus to penetrate and colonize the leaf tissue, causing tan-colored necrotic lesions to form at the site of infection. Severe infection reduces photosynthesis and causes premature defoliation, which ultimately decreases crop yield and seed quality. Eight genetic loci, Rpp1/Rpp1b to Rpp7 and Rpp6907, that confer race-specific resistance to P. pachyrhizi (Rpp) have been identified. Rpp2 was identified and characterized in the soybean accession PI 230970 and fine-mapped to a 188.1 kb interval on chromosome 16, a region predicted to contain several toll/interleukin-1 receptor nucleotide-binding leucine-rich repeat (TIR-NLR) genes. To identify Rpp2, we constructed a bacterial artificial chromosome (BAC) library from the resistant soybean accession PI 230970. Sequencing BACs that span the Rpp2 locus identified fourteen candidate genes with homology to the TIR-NLR family of resistance genes with integrated winged-helix (WH) domains. Of these, seven are predicted to encode full-length R proteins. Co-silencing the Rpp2 candidate genes compromised resistance in soybean accession PI 230970. Gene expression analysis suggests that a single gene, Rpp2C7_PI, which shares greatest homology to Rpp2C6_Wms82 (Glyma.16G136600) in the Williams 82 reference genome, is responsible for Rpp2-mediated resistance.