Plant Genome IV Conference Plant Genome IV Conference
Phytophthora root rot is a fungal disease caused by the pathogen Phytophthora megasperma Drechs. F. Sp. Glycinea T. Kuan & D.C. Erwin. This disease is second only to soybean cyst nematode in causing crop loss in soybean (Glycine max L. Merr.). Seven genes with alleles conferring resistance to the pathogen are known. Six of these genes have been placed on the soybean genetic map. A map-based gene cloning strategy has been implemented to clone Rps1, a resistance gene located on linkage group N. Rps1 is one of the most agriculturally important resistance genes and is used in many breeding programs. The locus is thought to include either a single gene which possesses multiple alleles, or to comprise a tightly linked cluster of genes. Near-isogenic lines for Rps1-c (Williams 79) and Rps1-k (Williams 82) have been compared to the recurrent parent, Williams, using 830 random oligonucleotide primers, RFLPs and microsatellite markers. A 37 cM region of donor DNA surrounding the Rps1 locus has been defined and the resistance gene has been mapped relative to these markers. A BAC library (3-5 genome equivalents) consisting of 150 kb average sized inserts has been developed to facilitate BAC-landing onto the Rps1 locus. Soybean sequences containing conserved motifs similar to other disease resistance genes have been amplified, sequenced and mapped in preparation of identifying putative resistance genes on BACs.