Molecular Breeding Strategies for Improvement of Complex Traits in Soybean

Soybean [Glycine max (L.) Merrill] is the leading oilseed crop grown in the world. Yield, fatty acids, protein, and oil are commercially important soybean traits; thus evaluation of breeding strategies for improvement of these traits is merited. To accomplish this, a comparison of molecular and phenotypic breeding strategies from progeny row selections was performed. From this it was determined that molecular strategies consistently outperformed phenotypic selections (PS) in the progeny row stage for soybean yield, fatty acids, protein, and oil. For yield, Epistacy was the preferred selection method. For fatty acids, protein, and oil, the genomic selection (GS) strategies were preferred. Additionally, a second comparison of molecular and phenotypic strategies was performed with selections from replicated field trials. These comparisons displayed mixed results except for yield, for which PS was the dominant method. With selection from replicated field trials, PS and GS methods were comparable for fatty acids, protein, and oil; indicating that either of these methods could be useful for making improvements. In addition to selection method evaluation, increased knowledge of genomic regions governing soybean yield, fatty acids, protein, and oil would be helpful. Thus, quantitative trait loci (QTL) detection was performed for these traits, with a total of 29 identified. Of these QTLs, three were candidates for confirmed status and four were candidates for positional confirmations. Additionally, possible candidate genes for soybean yield, fatty acids, protein and oil associated with QTLs in this study were identified; as were pleiotropic effects between protein and oil and between the fatty acids. The results from this research should be beneficial for those seeking to make soybean improvements. Researchers making selections from both progeny rows and replicated field trials can draw from these results when choosing which selection strategy to use. The gained knowledge of influential genomic regions for these traits can have application in improvement efforts. Future research seeking to implement high performing molecular breeding strategies and to identify causative genes for vi these and other QTLs impacting targeted traits will be important for the soybean breeding community.