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Title: New mutation in Delta-9-Stearoyl-Acyl Carrier Protein desaturase gene associated with enhanced stearic acid levels in soybean seed

Author
item BOERSMA, JEFFREY - University Of Guelph
item ABLETT, GARY - University Of Guelph
item GRAINGER, CHRISTOPHER - University Of Guelph
item Gillman, Jason
item Bilyeu, Kristin
item RAJCAN, ISTVAN - University Of Guelph

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2012
Publication Date: 6/12/2012
Citation: Boersma, J.G., Ablett, G.R., Grainger, C., Gillman, J.D., Bilyeu, K.D., Rajcan, I. 2012. New mutation in Delta-9-Stearoyl-Acyl Carrier Protein desaturase gene associated with enhanced stearic acid levels in soybean seed. Crop Science. 52:1736-1742.

Interpretive Summary: Stearic acid is a saturated fatty acid and is found as part of conventional soybean seed oil, but represents only a very minor component of the total oil (~3%). Stearic acid has utility for industrial purposes and has recently been demonstrated to be largely free of the negative health effects noted for other saturated fats. As a result, there has been increased interest in utilizing stearic acid in baking and other food applications. This is especially relevant as consumption of high levels of palmitic acid, the major component of palm oil, is strongly correlated with coronary heart disease. Several soybean mutant lines have been identified which feature elevations in stearic acid content (raising the level from 3% to ~10-26%), and one causative gene locus has been identified. Nevertheless, the genetics behind this trait remain illdefined, which has hindered the development of elevated stearic acid lines for industrial and food applications. Here we report on the identification of the genetic basis for elevated stearic acid content from two independent mutant lines. We have discerned specific mutations affecting a fatty acid biosynthetic gene as causative for the majority of the increase in stearic acid noted. We also describe the development of molecular genetic markers to directly select for the genetic cause of this valuable trait. The use of such markers has the potential to dramatically accelerate breeding efforts, increase the efficiency and reduce the costs involved in developing soybean lines with elevated stearic acid content.

Technical Abstract: Soybean [Glycine max (L.) Merr] oil from conventional cultivars typically contains ~3% stearic acid of the total seed oil. Increased stearic acid concentration in the seed oil of soybeans is desirable from both food and industrial use stand-points. To date a small number of mutants have been developed with increased stearic acid levels three to six times that of normal. At least two such lines were found to possess separate mutations in delta-9-stearoyl-ACP-desaturase-C (SACPD-C) that dramatically increased seed stearic acid concentration. We now report additional independent mutations of this gene that increase seed stearic acid levels of the soybean germplasm line RG7 three-fold to ~ 11.6%. An F5 RIL population was developed to determine the relationship between the RG7 SACPD-C mutation and stearic acid concentration. Transgressive segregation in the progeny of the cross between mutant lines RG7 and RG2 further increases seed stearic acid to almost 18%, suggesting the presence of yet another gene having a significant effect on stearic acid accumulation. We also discerned an independent, presumably allelic, mutation within the SACPD-C gene in line RG8, which features an elevation of stearic acid (~10.6%). Molecular markers diagnostic for the RG7 and RG8 SACPD-C mutations were developed, enabling rapid selection for these mutations in the development of cultivars with enhanced seed stearic acid content in the seed oil.