Identification and molecular mapping of Rps14, a gene conferring broad-spectrum resistance to Phytophthora sojae in soybean.

KEY MESSAGE: A soybean landrace carries broad-spectrum resistance to Phytophthora sojae, which is conferred by a single gene, designated Rps14, on the short arm of chromosome 3. Phytophthora sojae is the causative agent for Phytophthora root and stem rot in soybean [Glycine max (L.) Merr.] and can be managed by deployment of resistance to P. sojae (Rps) genes. PI 340,029 is a soybean landrace carrying broad-spectrum resistance to the pathogen. Analysis of an F2 population derived from a cross between PI 340,029 and a susceptible cultivar 'Williams' reveals that the resistance to P. sojae race 1 is conferred by a single gene, designated Rps14, which was initially mapped to a 4.5-cM region on the short arm of chromosome 3 by bulked segregant analysis (BSA), and subsequently narrowed to a 1.48 cM region corresponding to 229-kb in the Williams 82 reference genome (Wm82 v2.a1), using F3:4 families derived from the F2 population. Further analysis indicates that the broad-spectrum resistance carried by PI 340,029 is fully attributable to Rps14. The genomic sequences corresponding to the defined Rps14 region from a set of diverse soybean varieties exhibit drastic NBS-LRR gene copy number variation, ranging from 3 to 17 copies. Ultimate isolation of Rps14 would be critical for precise selection and deployment of the gene for soybean protection.