Map Location of the <i>Rpp1</i> Locus That Confers Resistance to Soybean Rust in Soybean

<jats:title>ABSTRACT</jats:title><jats:p>Soybean rust (SBR), caused by <jats:italic>Phakopsora pachyrhizi</jats:italic>, was first discovered in North America in 2004 and has the potential to become a major soybean [<jats:italic>Glycine max</jats:italic> (L.) Merr.] disease in the USA. Currently, four SBR resistance genes have been identified but not mapped on the soybean genetic linkage map. One of these resistance genes is the <jats:italic>Rpp1</jats:italic> gene, which is present in the soybean accession PI <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://200492">200492</jats:ext-link> The availability of molecular markers associated with <jats:italic>Rpp1</jats:italic> 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 BC<jats:sub>5</jats:sub> Williams 82 isoline L85‐2378, which contains the <jats:italic>Rpp1</jats:italic> resistance allele from the soybean accession PI <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://200492">200492</jats:ext-link>, for candidate regions that might contain <jats:italic>Rpp1</jats:italic> One candidate region was found with the SSR marker BARC_Sct_187 on linkage group G. A population of BC<jats:sub>6</jats:sub>F<jats:sub>2:3</jats:sub> lines segregating for the <jats:italic>Rpp1</jats:italic> resistance locus was genotyped in this region on linkage group G followed by inoculation with the <jats:italic>P. pachyrhizi</jats:italic> isolate India 73‐1 in the USDA‐ARS Biosafety Level 3 Plant Pathogen Containment Facility at Ft. Detrick, MD. The <jats:italic>Rpp1</jats:italic> gene was mapped between SSR markers BARC_Sct_187 and BARC_Sat_064 on linkage group G.</jats:p>