A novel FAD2-1 A allele in a soybean plant introduction offers an alternate means to produce soybean seed oil with 85% oleic acid content

Abstract

The alteration of fatty acid profiles in soybean to improve soybean oil quality has been a long-time goal of soybean researchers. Soybean oil with elevated oleic acid is desirable because this monounsaturated fatty acid improves the nutrition and oxidative stability of soybean oil compared to other oils. In the lipid biosynthetic pathway, the enzyme fatty acid desaturase 2 (FAD2) is responsible for the conversion of oleic acid precursors to linoleic acid precursors in developing soybean seeds. Two genes encoding FAD2-1A and FAD2-1B were identified to be expressed specifically in seeds during embryogenesis and have been considered to hold an important role in controlling the seed oleic acid content. A total of 22 soybean plant introduction (PI) lines identified to have an elevated oleic acid content were characterized for sequence mutations in the FAD 2-1A and FAD2-1B genes. PI 603452 was found to contain a deletion of a nucleotide in the second exon of FAD2-1A. These important SNPs were used in developing molecular marker genotyping assays. The assays appear to be a reliable and accurate tool to identify the FAD 2-1A and FAD2-1B genotype of wild-type and mutant plants. PI 603452 was subsequently crossed with PI 283327, a soybean line that has a mutation in FAD2-1B. Interestingly, soybean lines carrying both homozygous insertion/deletion mutation (indel) FAD2-1A alleles and mutant FAD2-1B alleles have an average of 82-86% oleic acid content, compared to 20% in conventional soybean, and low levels of linoleic and linolenic acids. The newly identified indel mutation in the FAD2-1A gene offers a simple method for the development of high oleic acid commercial soybean varieties.

Combinations of mutant FAD2 and FAD3 genes to produce high oleic acid and low linolenic acid soybean oil

“…In the Columbia, MO environment it requires four mutant genes with the 17D FAD2-1A missense allleles contributing to the high oleic background to produce less than 3 % linolenic acid content consistently, and combining four genes could be more challenging for soybean breeders. Recently, our group has generated another source of high oleic acid soybeans with nearly 85 % oleic acid and less than 3 % linolenic acid content with a combination of a mutant FAD2-1A allele containing a single base deletion resulting in a frameshift and premature translation termination from PI 603452 and the missense mutant FAD2-1B gene from PI 283327 (Pham et al 2011). We anticipate that with this high oleic acid soybean background, similar to the situation with the null FAD2-1 alleles from M23, only one mutant FAD3 gene will be needed to lower the content of linolenic acid to below 3 % in Missouri production environments, and possibly two mutant FAD3 genes will be necessary to further reduce linolenic acid content to 1 % in cooler environments.…”

QTLomics in Soybean: A Way Forward for Translational Genomics and Breeding

“…In soybean, functional markers have been developed for several QTLs and a summary of these functional markers is presented in Table 4, which will be very useful for soybean molecular breeders for carrying out translational breeding in soybean. Pham et al (2010, 2011) used allele specific functional markers for FAD2-1A and FAD2-1B genes to combine mutant alleles in a single background. They identified soybean lines carrying both homozygous mutant FAD2-1A alleles and mutant FAD2-1B alleles producing >80% oleic acid content, compared to 20% in conventional soybean.…”

The Role of Genomics and Biotechnology in Achieving Global Food Security for High-Oleic Vegetable Oil

“…Furthermore the members of these subclasses may be distinguished by comparative differences in SNP patterns within FAD2 gene sequences. For example, two alleles of GmFAD2-1A and 12 distinct SNP based haplotypes of the GmFAD2-1B gene have been reported among only 22 Plant Introductions from the USDA Soybean Germplasm Collection that exhibited genetic variation in oleic acid concentration 49) . In subsequent breeding experiments, the genetic combination of recessive alleles (indel mutations) of both GmFAD2-1A and GmFAD2-1B produced hybrid progeny with about 80％ or more oleic acid in seed oil 47,50) .…”

“…In subsequent breeding experiments, the genetic combination of recessive alleles (indel mutations) of both GmFAD2-1A and GmFAD2-1B produced hybrid progeny with about 80％ or more oleic acid in seed oil 47,50) . It is not clear whether all of the GmFAD2-1B haplotypes 49) will confer the high-oleic phenotype when combined with the recessive GmFAD2-1A allele. However, the ability to identify haplotypes based on SNP patterns that are specific to each known FAD2-1 allele 50) and also ancillary genes (other than FAD2 genes) that are associated with high-oleic acid concentration in seed oil 51) has made it possible to track and manage the determinants of the high oleic trait among breeding populations or among proprietary cultivars.…”