Map Location of the Rpp1 Locus That Confers Resistance to Soybean Rust in Soybean

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 [Glycine max (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 Rpp1 gene, which is present in the soybean accession PI http://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 http://200492, for candidate regions that might contain Rpp1 One candidate region was found with the SSR marker BARC_Sct_187 on linkage group G. A population of BC6F2:3 lines segregating for the Rpp1 resistance locus was genotyped in this region on linkage group G 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. The Rpp1 gene was mapped between SSR markers BARC_Sct_187 and BARC_Sat_064 on linkage group G.

Molecular mapping of soybean rust resistance in soybean accession PI 561356 and SNP haplotype analysis of the Rpp1 region in diverse germplasm

“…SBR resistance alleles from the other four soybean accessions were previously mapped to the same region on chromosome 18 (Hyten et al 2007;Chakraborty et al 2009;Ray et al 2009). Although we could not use the same markers as in the previous studies, the physical locations of these markers on the G. max genome (assembly version 1.01) (http://soybase.org) could be directly compared.…”

“…Four soybean accessions, PI 200492 (Rpp1), PI 594538A (Rpp1-b), PI 587886 and PI 587880A, with SBR resistance genes that mapped to the Rpp1 region on chromosome 18 (Hyten et al 2007;Chakraborty et al 2009;Ray et al 2009), PI 561356, the cultivar Williams 82 as well as 33 major North American soybean ancestors that contribute at least 95 % of the alleles in North America cultivars released from 1947 and 1988 (Gizlice et al 1994) were used for SNP haplotype analysis in a 213-kb interval surrounding Rpp1 (Table 1). Seeds of the accessions were obtained from the USDA Soybean Germplasm Collection (Urbana, IL, USA).…”

“…Spores of the isolate were routinely increased on "Williams 82" and stored under liquid nitrogen. Inoculum preparation and plant inoculations were conducted as described by Hyten et al (2007). After inoculation, plants were incubated for 24 h at 20°C in a dew chamber and then moved to a greenhouse maintained at 20°C for 14 days until symptoms were ready to be scored.…”

“…Urediniospores collected from leaves of Williams 82 were suspended in sterile distilled water containing 0.01 % Tween 20 (sodium monolaurate) and inoculated plants were incubated inside a dew chamber set at 20°C for 24 h (Pham et al 2009). For the ZM01-1 test, two replications of 12 plants of each PI and Williams 82 were tested and inoculations were conducted as described by Hyten et al (2007). The responses to isolates FL07-1 and ZM01-1 (IM, RB or TAN) were evaluated 15 days after inoculation.…”

“…Rpp1 from PI 200492 (Hyten et al 2007), Rpp1-b from PI 594538A (Chakraborty et al 2009) and SBR resistance genes from PI 587886 and PI 587880A (Ray et al 2009) were mapped to the same region on soybean chromosome 18 [linkage group (LG) G]. Rpp2 (Silva et al 2008) was mapped on chromosome 16 (LG J), Rpp3 ) and Rpp?…”