Submitted to: Genome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2001
Publication Date: N/A
Interpretive Summary: The soybean cyst nematode (SCN) is the major pest of soybean and causes an estimated $1 billion loss in soybean in the USA annually. The most practical management strategy has been the use of resistant cultivars. One soybean gene conferring partial resistance to SCN is the Rhg4 resistance allele on Linkage Group A2 of the soybean genetic map. We cloned a large piece of DNA near this gene from the soybean cultivar Williams 82 which is susceptible to attack by the SCN. We identified landmark pieces of DNA and used those landmarks to identify DNA from the same region of a soybean accession which is resistant to all known races of SCN. Our studies indicate that the Rhg4 gene may be located in a piece of this cloned DNA that is present in resistant genome, but that is absent in the Williams 82 genome. This information is useful to soybean researchers interested in cloning SCN resistance genes, because it provides DNA markers for the region around an important gene conferring resistance to the SCN, which could lead to cloning of the gene.
Technical Abstract: The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is the foremost pest of soybean (Glycine max L.Merr.) and is responsible for the loss of more than $1 billion annually. The most practical management strategy has been the use of resistant cultivars. The rhg1 resistance allele on Linkage Group G and the Rhg4 resistance allele on Linkage Group A2 of the soybean genetic map are especially important. Markers closely linked to the Rhg4 locus were used to screen a bacterial artificial chromosome (BAC) library of susceptible 'Williams 82' and identified a 150kb BAC. End-sequenced Eco R I subclones located to an Apa I restriction map provided landmarks for use in identifying the same region in a BAC library of the soybean accession PI 437.654, resistant to all known races of SCN. Eighty-seven PI 437.654 BACs were assigned to contigs at stringency levels ranging from 1e-05 to 1e-12. Two contigs represented the PI 437.654 counterpart of the Williams 82 BAC. Primers derived from end-sequences of BACs connected the two contigs. The two PI 437.654 contigs are of greater physical distance than the 150 kb Williams 82 BAC, and some primers amplify bands from the mid-portion of the PI 437.654 BAC contig that are not amplified from the Williams 82 BAC. These observations suggest that the Rhg4 gene may be located in an insertion in the PI 437.654 genome relative to the Williams 82 genome. This information is important to researchers interested in cloning soybean cyst nematode resistance genes, because it provides molecular markers for the region around an important gene conferring resistance to the soybean cyst nematode, which could lead to cloning of the gene.