| Summary: | <p>Abstract</p> <p>Background</p> <p>A series of <it>Rps </it>(resistance to <it>Pytophthora sojae</it>) genes have been protecting soybean from the root and stem rot disease caused by the Oomycete pathogen, <it>Phytophthora sojae</it>. Five <it>Rps </it>genes were mapped to the <it>Rps1 </it>locus located near the 28 cM map position on molecular linkage group N of the composite genetic soybean map. Among these five genes, <it>Rps1</it>-k was introgressed from the cultivar, Kingwa. <it>Rps1</it>-k has been providing stable and broad-spectrum <it>Phytophthora </it>resistance in the major soybean-producing regions of the United States. <it>Rps1</it>-k has been mapped and isolated. More than one functional <it>Rps1</it>-k gene was identified from the <it>Rps1</it>-k locus. The clustering feature at the <it>Rps1</it>-k locus might have facilitated the expansion of <it>Rps1</it>-k gene numbers and the generation of new recognition specificities. The <it>Rps1</it>-k region was sequenced to understand the possible evolutionary steps that shaped the generation of <it>Phytophthora </it>resistance genes in soybean.</p> <p>Results</p> <p>Here the analyses of sequences of three overlapping BAC clones containing the 184,111 bp <it>Rps1</it>-k region are reported. A shotgun sequencing strategy was applied in sequencing the BAC contig. Sequence analysis predicted a few full-length genes including two <it>Rps1</it>-k genes, <it>Rps1</it>-k-1 and <it>Rps1</it>-k-2. Previously reported <it>Rps1</it>-k-3 from this genomic region <abbrgrp><abbr bid="B1">1</abbr></abbrgrp> was evolved through intramolecular recombination between <it>Rps1</it>-k-1 and <it>Rps1</it>-k-2 in <it>Escherichia coli</it>. The majority of the predicted genes are truncated and therefore most likely they are nonfunctional. A member of a highly abundant retroelement, <it>SIRE1</it>, was identified from the <it>Rps1</it>-k region. The <it>Rps1</it>-k region is primarily composed of repetitive sequences. Sixteen simple repeat and 63 tandem repeat sequences were identified from the locus.</p> <p>Conclusion</p> <p>These data indicate that the <it>Rps1 </it>locus is located in a gene-poor region. The abundance of repetitive sequences in the <it>Rps1</it>-k region suggested that the location of this locus is in or near a heterochromatic region. Poor recombination frequencies combined with presence of two functional <it>Rps </it>genes at this locus has been providing stable <it>Phytophthora </it>resistance in soybean.</p>
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