Author
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Seiler, Gerald |
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Submitted to: Helia
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/15/2004 Publication Date: 8/14/2004 Citation: Seiler, G.J. 2004. Wild Helianthus annuus, a potential source of reduced palmitic and stearic fatty acids in sunflower oil. Helia. 27(40):55-62. Interpretive Summary: In recent years consumers have become more concerned about the consumption of saturated fats in their diet. High levels of saturated fat consumption may contribute an increase in blood serum cholesterol, and high blood serum cholesterol increases the risk of heart disease. Prompted by nutritional recommendations to consume fats lower in saturates and food manufacturers' interest in reducing the use of hydrogenated oil, food processors have become interested in oils with specific fatty acid profiles. Vegetable oils are the principal source of fats in many diets. Compared to other edible vegetable oils, the saturated fatty acid concentration in sunflower oil of 12% is considered moderate, with the principal saturated fatty acids being palmitic (6.5%) and stearic (4.5%) acids. Canola oil has only 4% palmitic and 2% stearic acids which is considered low in saturated fats. A reduction of saturated fatty acids in sunflower oil to the 6 to 8% level would increase the acceptability of sunflower oil as a healthier edible oil. The genus Helianthus contains 50 species, 36 perennial and 14 annual. Wild sunflower species serve as a potential resource for improving fatty acid composition in cultivated sunflower. The objective of this preliminary study was to search the vast genetic diversity available from wild annual sunflower, Helianthus annuus, the closest relative of the cultivated sunflower, for potential sources of reduced saturated fatty acids; less than 7.0% combined palmitic and stearic fatty acids. The survey found the average palmitic acid concentration in the populations ranged from 3.9 to 6.5% for the populations. Average stearic acid concentrations ranged from 1.9 to 3.0%. Achene oil of one population of wild annual sunflower, the closest relative of cultivated sunflower, ANN-2229 from Holmquist, South Dakota, had a palmitic acid level that averaged 3.9%, while stearic acid averaged 1.9%. The combined 5.8% palmitic and stearic acids is 50% lower than the present level of these fats in sunflower oil. When grown in the greenhouse, the saturated palmitic acid averaged 4.0%, while stearic acid averaged 1.9%, similar to the original population. This would indicate that palmitic and stearic acids have a genetic base with the potential for selection and incorporation into cultivated sunflower. Crossing this population with an inbred cultivated line produced early generation plants with achene oil that averaged 4.5% palmitic and 2.6% stearic acid, for a total of 7.1%. The inbred cultivated parent averaged 6.5% palmitic and 4.2% stearic acid totaling 10.7%. Preliminary information indicates that palmitic and stearic fatty acids in sunflower oil can be reduced by introducing genes from a population of a wild annual progenitor into cultivated sunflower. Further research will be needed to determine the inheritance of these fatty acids. Acceptable agronomic traits will also have to be bred into the lines and monitored during the introduction of the genes into cultivated sunflower. Technical Abstract: The current trend in human diets is to decrease consumption of the saturated palmitic and stearic fatty acids. Healthy diets restricting not only total fat, but the saturated portion of that fat, would decrease blood serum cholesterol and the risk of heart diseases. Edible vegetable oils are the principal source of fats in many diets. Sunflower oil, which is fifth in production among edible vegetable oils in the world, contains 65 g kg-1 saturated palmitic and 45 g kg-1 saturated stearic acids. These concentrations are high compared to rapeseed oil with 40 g kg-1 palmitic and 20 g kg-1 stearic acids. A reduction of saturated fats in traditional sunflower oil would lead to a healthier edible oil. The objective of this preliminary study was to search the vast genetic diversity available from wild Helianthus annuus, the closest relative of the cultivated sunflower, for potential sources of reduced saturated fatty acids; less than 70 g kg-1 combined palmitic and stearic fatty acids. Achenes of eighty-two populations of wild H. annuus were collected from the central Great Plains of the USA. Composited 20-achene samples from each population were analyzed for saturated fatty acids using organic base-catalyzed transesterification of fatty acid methyl esters and capillary gas chromatography. The average palmitic acid concentration ranged from 39 to 65 g kg-1 for the populations. Average stearic acid concentrations ranged from 19 to 37 g kg-1. Achene oil of one population of wild H. annuus from Holmquist, South Dakota, USA had a palmitic acid concentration averaging 39 g kg-1, while stearic acid averaged 19 g kg-1. The combined 58 g kg-1 palmitic and stearic acids is almost 50% lower than the present level of these fatty acids in sunflower oil. The level of saturated fatty acids observed in the population remained low when plants were grown in the greenhouse under uniform conditions. In the greenhouse, palmitic acid concentration of this population averaged 40 g kg-1, while stearic acid averaged 19 g kg-1. Crosses between this population and an inbred cultivated line produced F1 plants with an achene oil that averaged 39 g kg-1 palmitic and 21 g kg-1 stearic acid. In comparison, the inbred cultivated parent averaged 61 g kg-1 palmitic and 51 g kg-1 stearic acid. F2 plants produced achene oil that averaged 45 g kg-1 palmitic and 23 g kg-1 stearic acid, for a total of 68 g kg-1. When F1 plants were backcrossed to the cultivated inbred, BC1F1 plants produced achene oil that averaged 45 g kg-1 palmitic and 26 g kg-1 stearic acid for a total of 71 g kg-1. In comparison, the inbred cultivated parent averaged 65 g kg-1 palmitic and 42 g kg-1 stearic acid, for a total of 107 g kg-1. Preliminary information indicates that palmitic and stearic fatty acids in sunflower oil can be reduced by introducing genes from a wild annual population into cultivated sunflower. Further research will be needed to determine the inheritance of these fatty acids. Other agronomic traits will also have to be monitored during introgression of the fatty acids genes. |
