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Title: MAP LOCATION OF THE RPP1 LOCUS THAT CONFERS RESISTANCE TO PHAKOPSORA PACHYRHIZI (SOYBEAN RUST) IN SOYBEAN

Author
item Hyten, David
item Hartman, Glen
item Nelson, Randall
item Frederick, Reid
item CONCIBIDO, V - MONSANTO COMPANY
item Cregan, Perry

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2006
Publication Date: 1/1/2007
Citation: Hyten, D.L., Hartman, G.L., Nelson, R.L., Frederick, R.D., Concibido, V.C., Cregan, P.B. 2007. Map location of the Rpp1 locus that confers resistance to Phakopsora pachyrhizi (soybean rust) in soybean. Crop Science. 47:837-840.

Interpretive Summary: Soybean rust, caused by Phakopsora pachyrhizi, may become a major soybean disease in the United States since its recent discovery in the U.S. in 2004. It can cause yield losses ranging from 13 to 80% and most cultivars grown in the U.S. are highly susceptible to soybean rust which could lead to significant yield losses and major economic damage to U.S. soybean production. Four known genes that control resistance to soybean rust have been defined. We used molecular markers known as simple sequence repeats (SSRs) to determine the position on the soybean chromosomes of one of these genes which is known as Rpp1. The SSR genetic marker we identified allowed us to predict which soybean breeding lines carry the Rpp1 resistance gene. This marker, BARC-Sct_187, is 99.2% accurate in predicting whether a soybean breeding line carries the Rpp1 resistant gene. This marker will be useful for integrating the Rpp1 soybean rust resistant gene into modern cultivars, to combine it with other identified resistant genes for soybean rust, and to help determine the exact location of this resistant gene for molecular cloning. This information will be used by crop breeders and seed companies to increase the efficiency of incorporating this resistant gene into new soybean cultivars.

Technical Abstract: Soybean rust (SBR), caused by Phakopsora pachyrhizi, was first discovered in North America in 2004 and has the potential to become a major soybean disease in the United States.. There are currently four SBR resistance genes that have been identified but not mapped on the soybean genetic linkage map. One of these resistant genes is the Rpp1 gene which is present in the soybean accession PI 200492. The availability of molecular markers associated with Rpp1 will permit marker-assisted selection and expedite the incorporation of this gene into U.S. cultivars. We compared simple sequence repeat (SSR) markers between ‘Williams 82’ and the BC5 Williams 82 isoline L85-2378 which contains the Rpp1 resistance allele from the soybean accession PI 200492 for candidate regions which might contain Rpp1. One candidate region was found with the SSR marker BARC_Sct_187 on linkage group G. A population of BC6F2 lines segregating for the Rpp1 resistance locus was genotyped with Sct_187 followed by inoculation with the P. pachyrhizi isolate India 73-1 in the USDA-ARS Biosafety Level 3 Plant Pathogen Containment Facility at Ft. Detrick, MD. Sct_187 was tightly linked to the Rpp1 gene with a genetic distance of 0.8 cM. This marker will be useful for integrating Rpp1 resistance into modern cultivars.