Soybean Genome Sequencing Project:

There are several loci in the soybean genome that are known to confer resistance to the soybean cyst nematode (SCN).  Two important loci are designated Rhg1 and Rhg4. These two loci are responsible for most resistance to SCN.  The Rhg₁ locus is located on Linkage Group G of the soybean map, while the Rhg₄ locus is located on Linkage Group A2.  Our laboratory constructed a soybean map using genetic mapping techniques and molecular markers.  The Rhg₄ locus is closely linked to the I locus conferring black seed coat.  We identified markers residing close to the I locus, hecn to the Rhg₄ locus.  One marker, the RFLP marker pBLT65, mapped very close to the Rhg₄ locus and was used in a screen to clone the locus to clone the gene by map position.  See Cloning by map position.

We identified a 145 kb portion of the genome near or containing the rhg₄ locus in the SCN-sensitive soybean cultivar Williams.  We used developed numerous molecular markers from this piece of DNA to identify the similar portion of DNA from the genome of an SCN-resistant soybean genotype, PI437.654.  We have approximately 600 kb of DNA cloned from PI437.654 at the Rhg₄ locus, including DNA containing the I locus and containing pBLT65.

DNA sequence from Williams and PI437.654 will be annotated and compared.  The portion of our web site containing the annotated DNA sequence of this region from the two genotypes is under construction.