ARS | Publication request: Fine Mapping the Soybean Aphid Resistance Gene Rag1 in Soybean

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 30, 2009
Publication Date: March 1, 2010
Repository URL: http://hdl.handle.net/10113/47270
Citation: Kim, K.S., Bellendir, S., Hudson, K. A., Hill, C.B., Hartman, G.L., Hyten, D., Hudson, M.E., Diers, B.W. 2010. Fine mapping the soybean aphid resistance gene Rag1 in soybean. Theoretical and Applied Genetics. 20(5):1063-1071.

Interpretive Summary: In this study, the Rag1 gene, which confers soybean plants with resistance to soybean aphid was genetically mapped using a number of new molecular markers. Using the newly available soybean genome sequence, it is possible to narrow down the region of the soybean genome that contains the resistance gene to 115 kilobases. This defined genetic interval contains a number of genes that can now be tested as candidates for Rag1 This information will be useful to soybean breeders in their attempts to incorporate the aphid resistance trait into plants, and the methods used to identify molecular markers can be applied to mapping a number of different traits in many crop species. Knowledge of the identity of the gene that confers aphid resistance and understanding of the mechanism of resistance will be useful to scientists to understand how soybean and other plant species resist insect pests.

Technical 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 centiMorgan (cM) marker interval on soybean chromosome 7 [formerly linkage group (LG) M]. The development of additional genetic markers more closely linked to Rag1 was needed to accurately position the gene to improve the effectiveness of marker-assisted 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 fine map of the Rag1 interval, 824 BC4F2 and 1,000 BC4F3 plants segregating for the gene were screened with markers flanking Rag1. Plants with recombination events close to the gene were tested with SNPs identified in previous studies along with new SNPs identified using the Williams 82 draft soybean genome sequence and gene-scanning melt-curve analysis. Progeny of these recombinant plants were evaluated for aphid resistance. These efforts 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 draft genome of 115 kb. Markers identified in this study that are closely linked to Rag1 will be a useful resource in MAS for this gene. In addition, several candidate genes for Rag1 are present within the 115 kb interval.