Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/16/2007
Publication Date: 7/30/2007
Citation: Chappell, A.S., Bilyeu, K.D. 2007. The low linolenic acid soybean line PI 361088B contains a novel GmFAD3A mutation. Crop Science. 47(4):1705. Interpretive Summary: Health concerns surrounding the intake of trans fatty acids in the diet have driven interest in the production of vegetable oils stable for cooking and frying that do not contain trans fats. Linolenic acid is the major unstable component of vegetable oil and its reduction is the reason for hydrogenation and creation of trans fats in soybean oil. Plant breeding efforts have centered on the desire to generate soybean varieties that produce good yields of stable oil which contain no trans fatty acids through genetic reductions in linolenic acid. In the work described in this manuscript, a soybean plant introduction breeding line containing reduced levels of linolenic acid was characterized at the molecular level in an effort to improve breeding resources for low linolenic acid content in soybean oil. We identified a mutation in a candidate fatty acid desaturase gene. New molecular markers were developed to allow soybean breeders to efficiently capture the trait when developing new soybean varieties. The impact of these results is the expansion of the tools available to plant breeders that are trying to incorporate the low linolenic acid trait into other elite lines and to more rapidly develop new varieties that will offer more desirable oil characteristics for the U.S. soybean products market.
Technical Abstract: Characterization of genetic mutations at the molecular level allows for the development of perfect genetic markers and rapid assays to detect those markers, which enables breeders to directly select for desired alleles in early generations of segregating populations. The objective of this study was to identify any genetic lesions found in the GmFAD3A gene in the low linolenic acid soybean (Glycine max (L.) Merr) line, PI 361088B, which contains a fan allele and 38.1 g/kg linolenic acid in the seed oil. An additional objective was to develop rapid molecular marker assays that distinguish between the wild-type and PI 361088B alleles. The entire genomic sequence of the GmFAD3A gene in PI 361088B was determined and 3 PCR-based assays were developed. Two thymine nucleotides are inserted into a run of four thymines from nucleotide position 307 to 310 of the GmFAD3A coding sequence, resulting in a frame-shift and the introduction of a premature stop codon at nucleotide 328. Presumably this insertion results in a null allele. Two molecular marker assays were developed that rely on PCR amplification of the region of interest followed by restriction endonuclease digestion and agarose gel electrophoresis or melting curve analysis. A third assay is an allele-specific PCR-based assay that does not require any endonuclease step and requires only melting curve analysis. In conclusion, the low linolenic acid soybean line PI 361088B contains a coding mutation in GmFAD3A; this allele can easily be distinguished from the corresponding wild-type allele using any of three rapid molecular marker assays that were developed.