Fine Mapping Soybean Aphid Resistance Gene rag1c in Soybean (Glycine max L.)

The soybean aphid (Aphis glycines Matsumura) is a new invasive soybean pest and can cause severe yield loss without treatment. Use of aphid resistant cultivars is a promising solution to control soybean aphid. In our Soybean Breeding program at Michigan State University (MSU), two soybean aphid resistance gene, rag1c and rag4, were identified in PI 567541B (Mensah et al. 2008) and they were later mapped to the soybean chromosome 7 (LG M) and chromosome 13 (LG F), respectively. These two genes explained 31-88% of the phenotypic variations in the trials (Zhang et al. 2009). The objectives of this study were: (1). fine mapping the soybean aphid resistance rag1c gene using the high generation residual heterozygous lines (RHL) and large fine mapping populations; (2) analysis of the candidate gene expression. To fine map the rag1c gene derived from PI 567541B, various approaches were carried out in this study. The rag1c gene was fine mapped in a 96 kbp interval flanked by the customer designed KASPar® SNP MSUSNP7-32 (Chromosome 7) and MSUSNP7-20 (Chromosome 7) based on the recombination events that resulted in the variation of the aphid resistance in the fine mapping lines. Moreover, the preliminary gene expression analysis indicated that the transcript abundance (TA) of the candidate rag1c gene in the interval was distinguished to the fine mapped Rag1 gene. The results of gene fine mapping and gene expression analysis in this study suggest that the interval defined by SNP markers MSUSNP7-32 and MSUSNP7-20 possesses the candidate gene rag1c.