Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2007
Publication Date: 3/1/2008
Citation: Bachlava, E., Dewey, R., Auclair, J., Wang, S., Burton, J.W., Cardinal, A. 2008. Molecular mapping of genes encoding microsomal omega-6 desaturase enzymes and their cosegregation with QTL affecting oleic acid content in soybean. Crop Science, 48:640-650. Interpretive Summary: Soybean oil would be more stable when used for frying and food fried in the oil would have a better flavor if the oleic acid content of the oil were increased to a mid-level. Mid-oleic soybean oil has about 60% oleic acid compared with 20% oleic acid for regular soybean. Genes in developing seeds that determine how much oleic acid in the final seed oil are called FAD genes. There are two classes of these genes, FAD2-1 and FAD2-2. The objective of this research project was to locate the FAD genes in the soybean genome. A linkage analysis of two populations of soybeans showed that one of the FAD2-1 genes FAD2-1A is located on linkage group 0 and the other, FAD2-1B is located on linkage group L. The two FAD2-2 genes are located on linkage groups I and L. The genes are linked to DNA markers, which can be used in soybean breeding research to develop mid-oleic soybean varieties.
Technical Abstract: The microsomal omega-6 desaturase enzymes, which catalyze the desaturation of oleic acid to linoleic acid during fatty acid biosynthesis, are encoded by the FAD2-1 and FAD2-2 genes in soybeans. Breeders aim to incorporate the high oleate trait into soybean germplasm in order to improve the nutritional value and oxidative stability of soybean oil. The objectives of this study were to map the isoforms of the FAD2-1 and FAD2-2 genes and investigate the association of these genetic loci with the oleate phenotype in three populations segregating for oleate content. The populations were grown in replicated multi-environment field trials. According to linkage analysis conducted for two of the populations, FAD2-1A and FAD2-1B mapped on linkage groups 0 and I, respectively, while the closely linked FAD2-2A and FAD2-2B isoforms mapped on linkage group L. Oleate QTL with minor effects were detected in the proximity of FAD2-1B and possibly FAD2-2B on linkage groups I and L. QTL affecting maturity were also detected on chromosomal regions adjacent to the GmFAD2 genes. The genotyping assays developed for the FAD2-1A, FAD2-1B, and FAD2-2B isoforms, as well as their linked SSR markers, can be used in soybean breeding programs for the elevation of oleic acid seed content through marker-assisted selection.