Improving Nebraska's Soybean Protein & Oil Content

Impact on Soybean Production and Value

The detection of genes that influence the protein and oil composition value of soybean seed will be important for public and proprietary breeders to introduce these traits into high yielding soybean varieties

James Specht and George Graef (2011)


Key Terminology

Linkage map is a map of genes on a chromosome based on their likelihood of being inherited together. This gives a relative distance between genes, but not a physical distance.

Alleles are alternative forms of the same gene that are located on different chromosomes.

Near isogenic lines (NILs) are breeding lines that are genetically identical except for specific regions of interest that are associated with a gene, or genes, of interest. This allows researchers to study the effects of the genes of interest without the influence of other genetic variability.

Single nucleotide polymorphism (SNP) is the common variation of a single nucleotide in the DNA sequence of members within a species. They occur throughout the genome and can be used as molecular markers to map genes

Germplasm refers to the total genetic material available for study – mainly from the genetic material represented in the available accessions

Quantitative traits are traits, or phenotypes, that are influenced by two or more genes and the environment.

Quantitative trait loci (QTL) are regions of DNA that contain, or are closely linked to, genes of quantitative traits.


Study Objectives

1. Determine the linkage map positions for all genes (QTLs) that influence soybean seed protein and oil content.

2. Identify flanking markers for each gene that can be used by USA soybean breeders to track and introgress genes for high protein and oil into high yielding varieties.

3. Once the QTL alleles and flanking markers are identified, start the introgression process for Nebraska bred varieties.


Findings

We used 48 matings of high protein germplasm plant introductions to high yielding varieties to detect what we believe to be nearly all of major QTLs that control soybean seed protein content. We also used matings of two very high seed oil content breeding lines to a high yield variety and to each other to detect QTLs that control soybean seed oil content. Flanking SNPs were identified for seed protein QTLs detected on soybean chromosomes 2, 3, 4, 5, 6, 7, 8, 10, 14, 15, 18, and 20, and of these, the QTLs detected on 2, 7, 10, 14, 16, and 18 are new discoveries. The high-protein alleles at these QTLs should be useful in developing soybean varieties with sufficient seed protein levels that can generate the higher valued 48% protein meal.

Flanking SNP markers were also identified for seed oil QTLs detected on 6, 7, 10, 11, 15, 17, and 19. The high-oil alleles at these QTLs should be useful in developing soybean varieties with higher oil content that may be of value to the soybean biodiesel industry. As noted in Objective 3 above, we have started to mate the progeny lines that have multiple high protein QTL alleles and/or high oil QTL alleles into our highest yielding Nebraska breeding lines.


Next Steps

We will prepare a factorial set of near-isogenic lines (NILs) for each protein QTL to determine what combination of high protein alleles can provide high protein seed content with minimal impact on soybean yield.

We also will prepare a similar factorial set of NILs for each oil QTL.