Mapping and confirmation of two genes conferring resistance to soybean rust (Phakopsora pachyrhizi) in the soybean line UG-5 (Glycine max)

Development of durable resistance to soybean rust (SBR) is challenging due to the pathogenic diversity ofPhakopsora pachyrhizipopulations. The objective of this research was to investigate and confirm the genomic locations ofRppgenes in the Ugandan line UG-5 that confer resistance to different SBR pathotypes. Bulked segregant analysis revealed two genomic regions associated with resistance in a cross with rust-susceptible 'Williams 82'. Composite interval mapping in the F(2)and F(2:3)populations had a LOD score of 48.7 in a region 0.38 cM away from the estimated location of theRpp1locus on chromosome (Chr.) 18. An approximately 23-Kbp interval spanning theRpp1locus was flanked by SNP markers ss715632313 and ss715632318. Another interval was identified at theRpp3locus on Chr. 6 between markers Satt100 and ss715594488 (2.4 cM) in the F(2)population and between Satt100 and ss715594874 (4.3 cM) in the F(2:3)population, with a maximum LOD score of 25.6. UG-5 was thus confirmed to have SBR resistance genes at theRpp1andRpp3loci that can be pyramided into other elite cultivars.