Mapping Genes Encoding Microsomal Omega-6 Desaturase Enzymes and Their Cosegregation with QTL Affecting Oleate Content in Soybean

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 soybean [Glycine max (L.) Merr.]. 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 multienvironment field trials. According to linkage analysis conducted for two of the populations, FAD2-1A and FAD2-1B mapped on Linkage Groups O and I, respectively, while the closely linked FAD2-2A and FAD2-2B isoforms mapped on Linkage Group L. Oleate quantitative trait loci with minor effects were detected in the proximity of FAD2-1B and possibly FAD2-2B on Linkage Groups I and L. Quantitative trait loci affecting maturity were also detected on chromosomal regions adjacent to the FAD2 genes. The genotyping assays developed for the FAD2-1A, FAD2-1B, and FAD2-2B isoforms, as well as their linked simple sequence repeat markers, can be used in soybean breeding programs for the elevation of oleic acid seed content through marker-assisted selection.