A novel Phakopsora pachyrhizi resistance allele (Rpp) contributed by PI 567068A

Abstract

The Rpp6 locus of PI 567102B was mapped from 5,953,237 to 5,998,461 bp (chromosome 18); and a novel allele at the Rpp6 locus or tightly linked gene Rpp[PI567068A] of PI 567068A was mapped from 5,998,461 to 6,160,481 bp. Soybean rust (SBR), caused by the obligate, fungal pathogen Phakopsora pachyrhizi is an economic threat to soybean production, especially in the Americas. Host plant resistance is an important management strategy for SBR. The most recently described resistance to P. pachyrhizi (Rpp) gene is Rpp6 contributed by PI 567102B. Rpp6 was previously mapped to an interval of over four million base pairs on chromosome 18. PI 567068A was recently demonstrated to possess a resistance gene near the Rpp6 locus, yet PI 567068A gave a differential isolate reaction to several international isolates of P. pachyrhizi. The goals of this research were to fine map the Rpp6 locus of PI 567102B and PI 567068A and determine whether or not PI 567068A harbors a novel Rpp6 allele or another allele at a tightly linked resistance locus. Linkage mapping in this study mapped Rpp6 from 5,953,237 to 5,998,461 bp (LOD score of 58.3) and the resistance from PI 567068A from 5,998,461 to 6,160,481 bp (LOD score of 4.4) (Wm82.a1 genome sequence). QTL peaks were 139,033 bp apart from one another as determined by the most significant SNPs in QTL mapping. The results of haplotype analysis demonstrated that PI 567102B and PI 567068A share the same haplotype in the resistance locus containing both Rpp alleles, which was designated as the Rpp6/Rpp[PI567068A] haplotype. The Rpp6/Rpp[PI567068A] haplotype identified in this study can be used as a tool to rapidly screen other genotypes that possess a Rpp gene(s) and detect resistance at the Rpp6 locus in diverse germplasm.

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

“…Thirteen of the 25 assays (11 near Rpp1 and two near the Rpp3 locus) detected polymorphisms between UG‐5 and 'Williams 82' (Table S1). The master mix and PCR cycling conditions used for the KASP assays were the same as those previously described by King et al (2016a). Endpoint readings were determined using a Roche LightCycler 480 II with LightCycler ® Software 2.0 (Roche Diagnostics Corporation Indianapolis).…”

“…The Rpp1 , Rpp4 and Rpp6 loci are located on chromosome (Chr.) 18 (Chakraborty et al, 2009; Garcia et al, 2008; Hossain et al, 2015; Hyten et al, 2007; King et al, 2016a; Li et al, 2012). The Rpp2 gene was mapped to Chr.…”

Soybean Crop: A Review on the Biotechnological Advances and Expectation for Modern Cultivars

“…Searching for resistant genotypes, the United States formalized a trademark for the Rpp5 gene selection, which promotes resistance to Asian rust (King et al, 2016). The method facilitates the development of resistant varieties to this pest.…”

Prospects for Durable Resistance Against an Old Soybean Enemy: A Four-Decade Journey from Rpp1 (Resistance to Phakopsora pachyrhizi) to Rpp7

“…Multiple alleles of Rpp genes exist in soybean genomes, which show differential responses to selected P. pachyrhizi pathotypes or demonstrate different gene actions [56,62,71,77,82]. For instance, Chakraborty et al, [62] showed that a P. pachyrhizi isolate from Zimbabwe (ZM01-1) produced RB lesions on soybean line PI 594538A, but TAN lesions on PI 200492, the original source of Rpp1.…”