Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 2001
Publication Date: N/A
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 10% of the annual U.S.soybean crop. 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 corresponding region in a BAC library of the soybean accession PI 437.654, with broad resistance to SCN. Restriction fragment analysis determined that two contigs represented the PI 437.654 counterpart of the Williams 82 BAC. Primers derived from end-sequences of BACs connected the two contigs. Some of the markers on the PI 437.654 contig are separated by a greater physical distance (ca. 100 kb) than in the 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 the presence of an insertion in the PI 437.654 genome relative to the Williams 82 genome. Subclones of two PI 437.654 BACs suspected to contain the Rhg4 allele have been end- sequenced. The sequences were compared with those in GenBank, and sequence similarities are reported. A physical comparison of genomes is presented. A high degree of multi-level duplication may be responsible for reported organizational instability in this part of the genome.