Precision Mapping of Soybean Seed Protein QTLs on Chromosome 10 in Six Populations

Hundreds of high protein soybean plant introductions (PIs) exist in the USDA germplasm collection, and are potential sources of high protein genes.  A quantitative trait locus (QTL) identification is the start to using marker-assisted selection (MAS) to introgress desirable QTL alleles into soybean cultivars.  A total of 48 F₂ populations were created from high protein germplasm accessions to high-yielding public cultivars. In six of the 48 F₂ populations, a strong soybean seed protein QTL was detected with selective genotyping and mapped on chromosome 10 [formerly linkage group (LG) O].  This QTL is not currently listed in SoyBase.  The objective of this study was to more precisely map the soybean high protein QTL on Chr. 10 and identify possible candidate genes.  All 1,237 individuals in these six F₂ populations were genotyped with additional markers located in the Chr. 10 region surrounding the QTL peak.  Twenty simple sequence repeat (SSR) assays and four custom Taqman single nucleotide polymorphism (SNP) assays were developed for this purpose.  This effort resulted in the mapping of this soybean protein QTL in an 8-cM interval in those six populations.  The putative gene models located in the genomic sequence comprising this 8-cM Chr. 10 region include many genes.  However, considering that the QTL controls the magnitude of the seed protein content, the amino acid transporter genes are certainly of possible candidate gene interest.  A fine-mapping of the QTL using heterogeneous inbred families will be needed to precisely position the QTL and thus improve the effectiveness of MAS and the ability to eventually clone the underlying gene.