ARS | Publication request: Screening for differential resistance responses to Phakopsora pachyrhizi between Rpp3, Rpp?(Hyuuga) and 12 additional soybean accessions

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2010
Publication Date: June 1, 2010
Citation: Kendrick, M.D., Pedley, K.F., Frederick, R.D., Boerma, H.R. 2010. Screening for differential resistance responses to Phakopsora pachyrhizi between Rpp3, Rpp?(Hyuuga) and 12 additional soybean accessions. Phytopathology. 100:S61.

Technical Abstract: Asian soybean rust (ASR) is an economically significant disease caused by the fungus Phakopsora pachyrhizi. Five soybean genes that confer resistance to specific isolates of P. pachyrhizi (Rpp1 – Rpp5) were previously identified. More recently, the soybean cultivar Hyuuga (PI506764) was found to be resistant to field isolates of the pathogen. The genes Rpp?(Hyuuga) and Rpp3 map to the same region of chromosome 6, between markers Satt460 and Satt307, and Satt460 and Sat_263 respectively. Twelve additional soybean accessions with resistance to P. pachyrhizi and mapping within 5 cM of the Rpp3/Rpp?(Hyuuga) locus have been identified by a bulk-segregant approach. It is unknown whether the resistance genes in PI506764(Hyuuga), PI462312(Rpp3), and these 12 lines are identical, allelic, or independent genes. Previously it was reported that PI462312 (Rpp3) and PI506764 (Hyuuga) responded similarly when inoculated with 10 P. pachyrhizi isolates. However, when challenged with a Brazilian isolate, Rpp3 plants were susceptible while Rpp?(Hyuuga) were resistant, leading to the possibility that ‘Hyuuga’ may carry a unique allele at the Rpp3 locus or another resistance gene. To further characterize these 14 lines, we inoculated each with additional isolates. The differential responses that we observed suggest that two or more resistance alleles map to the same region of chromosome 6.