Novel alleles of FAD2-1A induce high levels of oleic acid in soybean oil

Soybean plays an important role in seed oil production for foods and industrial products in the USA. Chemical hydrogenation of commodity soybean oil increased functionality but unavoidably created trans fat which has been linked to many health issues in humans. An alternative to using hydrogenation of the oil to enhance oxidative stability is to genetically increase the level of oleic acid in the seed oil. Our goal was to develop a soybean germplasm as a source for more functional soybean oil with a high oleic acid, increased stearic acid, and low linolenic acid profile utilizing new and existing variant alleles of key fatty acid desaturase genes. Using forward genetics, novel alleles of FAD2-1A were discovered and characterized from a mutant soybean population already containing elevated seed stearic acid content. One of the two new FAD2-1A alleles, when combined with existing mutant alleles of FAD2-1B created a high oleic acid seed oil phenotype in soybean germplasm lines. The other new FAD2-1A allele produced lower and more variable oleic acid levels when combined with existing mutant alleles of FAD2-1B. Seed stearic acid increased to 10-11% in lines containing combinations of FAD2-1A and FAD2-1B mutant alleles plus the SACPD-C missense mutant alleles; however, the increase in stearic acid was associated with a decrease in the oleic acid content and did not meet the target of at least 20% stearic acid in the seed oil. In addition, existing FAD3 mutant alleles were incorporated into the novel high oleic acid and high oleic/elevated stearic acid soybean lines with four or five targeted alleles combined (FAD2-1A, FAD2-1B, FAD3A, FAD3C, and SACPD-C) to create soybean germplasm with more functional soybean oil. This study is beneficial for improving the quality of soybean oil based on nutritional value and oxidative stability.