Fine mapping the soybean aphid resistance gene Rag1 in soybean

Abstract

The soybean aphid (Aphis glycines Matsumura) is an important soybean [Glycine max (L.) Merr.] pest in North America. The dominant aphid resistance gene Rag1 was previously mapped from the cultivar 'Dowling' to a 12 cM marker interval on soybean chromosome 7 (formerly linkage group M). The development of additional genetic markers mapping closer to Rag1 was needed to accurately position the gene to improve the eVectiveness of markerassisted selection (MAS) and to eventually clone it. The objectives of this study were to identify single nucleotide polymorphisms (SNPs) near Rag1 and to position these SNPs relative to Rag1. To generate a Wne map of the Rag1 interval, 824 BC 4 F 2 and 1,000 BC 4 F 3 plants segregating for the gene were screened with markers Xanking Rag1. Plants with recombination events close to the gene were tested with SNPs identiWed in previous studies along with new SNPs identiWed from the preliminary Williams 82 draft soybean genome shotgun sequence using direct re-sequencing and gene-scanning melt-curve analysis. Progeny of these recombinant plants were evaluated for aphid resistance. These eVorts resulted in the mapping of Rag1 between the two SNP markers 46169.7 and 21A, which corresponds to a physical distance on the Williams 82 8£ draft assembly (Glyma1.01) of 115 kilobase pair (kb). Several candidate genes for Rag1 are present within the 115-kb interval. The markers identiWed in this study that are closely linked to Rag1 will be a useful resource in MAS for this important aphid resistance gene.

Mapping soybean aphid resistance genes in PI 567598B

“…The difference or similarity of action between dominant and recessive aphid resistance genes in soybeans remains to be investigated. The QTLs detected in this study are located in similar genomic regions as Rag1 on chromosome 7 (Li et al 2007, Kim et al 2010 and Rag3 on chromosome 16 (Zhang et al 2010). Although the two resistant genes in PI 567598B were considered recessive (Mensah et al 2008), and Rag1 or Rag3 was considered dominant or co-dominant (Hill et al 2006a;Zhang et al 2010), they may still be the same genes as Rag1 and Rag3, since the susceptible parent in this study was different from the ones used for characterizing Rag1 and Rag3.…”

Fine mapping of the soybean aphid-resistance gene Rag2 in soybean PI 200538

“…Both Rpg1-b and the third gene are outside the 54-kb region containing Rag2, so they are likely not Rag2. Our research on fine mapping Rag1 also showed that the 115-kb region including Rag1 contains two NBS-LRR genes (Kim et al 2010). These gene predictions for the Rag2 region are all based on the Williams 82 sequence and Williams 82 does not contain (Tamulonis et al 1997).…”

Detection of novel QTLs for foxglove aphid resistance in soybean

“…Thus, these putative R genes could be strong candidates for the major foxglove aphid resistance gene, Raso2. Among the previously reported soybean R genes, Rag1, soybean aphid resistance gene, was mapped to 115 kbp on chromosome 7 that corresponds to Raso2, and there are two candidate NBS-LRR genes in the Rag1 interval (Kim et al 2010a). However, the gene source of Rag1, cultivars 'Jackson' and 'Dowling', did not show the resistance responses to Korea biotype foxglove aphid in Fig.…”