HIGH-RESOLUTION GENETIC AND PHYSICAL MAPPING OF MOLECULAR MARKERS LINKED TO THE PHYTOPHTHORA RESISTANCE GENE RPS1-K IN SOYBEAN

The resistance of soybean to Phytophthora root and stem rot caused by Phytophthora sojae is conferred by a series of single-dominant Rps gen es, We have applied random amplified polymorphic DNA (RAPD) and amplif ied fragment length polymorphism (AFLP) analyses to isolate molecular markers linked to Rps1-k, Five RAPD markers were identified and mapped closely to one side of Rps1-k, AFLP analysis was carried out with nea r isogenic lines and bulks obtained from F-3 families. Twenty-seven ma rkers were identified, Nineteen of these were specific to the resistan t parent, Five AFLP markers were amplified from the susceptible parent , One of these markers, TC1, mapped at 0.07 centimorgans (cM) from the Rps1 locus, Three AFLP markers were co-dominant, and one of these, CG 1, mapped at a distance of 0.06 cM from the Rps1 locus on the opposite side of the rest of the markers, Two RAPD, 17 AFLP, and 14 restrictio n fragment length polymorphism (RFLP) markers originating from duplica ted sequences were mapped within a 3-cM map interval, These results su ggest that Rps1-k is located at the end of an introgressed region, Phy sical mapping data indicate that the Rps1-k-flanking markers CG1 and T C1 may be located within a 125-kb chromosomal fragment.