Submitted to: Trends in New Crops and New Uses
Publication Type: Book / chapter
Publication Acceptance Date: 12/22/2002
Publication Date: 12/22/2002
Citation: SEILER, G.J. POTENTIAL SOURCE OF REDUCED PALMITIC AND STEARIC FATTY ACIDS IN SUNFLOWER OIL FROM A POPULATION OF WILD HELIANTHUS ANNUUS. JANEIK, J., EDITOR. TRENDS IN NEW CROPS AND NEW USES. AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE PRESS. 2002. PP. 150-153. 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 to increased blood serum cholesterol, and high blood serum cholesterol increases the risk of coronary 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. Rapeseed 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. Accessions of wild sunflower species with lower saturated palmitic and stearic acids have been identified, but their stability and transfer into cultivated sunflower have not been documented. This study evaluates populations of wild annual H. annuus, the closest relative of cultivated sunflower, for reduced palmitic and stearic acids concentrations, to determine their stability and to explore the possibility of introgressing the reduced saturated fatty acid genes into cultivated sunflower. Of the individual populations analyzed, ANN-2229 (PI 586886) from Holmquist, South Dakota had the lowest palmitic acid concentration with 3.9% and the lowest stearic acid concentration with 1.9%, totaling 5.8%. This level is 50% lower than the level generally observed in oil of cultivated sunflower. This population was chosen to check the stability of the lower saturated fatty acids to see if the genes controlling these acids were dominant and if they could be transferred into cultivated sunflower. When progeny of ANN-2229 were grown in the greenhouse, the saturated fatty acids in achene oil was very similar to the levels observed in the original population. The reduced levels of saturated fatty acids observed in the original population appear to be stable, indicating the reduced levels of palmitic and stearic acids have a genetic base and the potential to be introgressed into cultivated sunflower. The first and second generation crosses with cultivated sunflower retained the reduced levels of saturated fatty acids with 4.0% palmitic and 2.0% stearic acids. Preliminary results indicate that introgressing genes from a population of the closest wild relative of the cultivated crop can reduce palmitic and stearic acid levels in sunflower oil. The genes appear to be relatively stable after transfer. Further research will be needed to study the inheritance of the genes controlling palmitic and stearic fatty acids and their relationship to other important traits. 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 present trend in human diets is to decrease the consumption of the saturated palmitic and stearic fatty acids. Healthy diets restricting not only total fat, but also the saturated portion of that fat would decrease blood serum cholesterol and the risk of coronary heart diseases. Edible vegetable oils are the principal source of fats in many diets. Sunflower oil, which is fourth in production among edible vegetable oils in the world typically contains 6.5% saturated palmitic and 4.5% saturated stearic fatty acids. These levels are high compared to rapeseed oil with 4% palmitic and 2% stearic fatty acids. A reduction of saturated fats in traditional sunflower oil would lead to a healthier edible oil. The objective of this study was to search the vast genetic diversity available from the wild ancestors of the cultivated sunflower for a potential source of reduced saturated fatty acids. A survey of wild annual Helianthus annuus, the closest relative of the cultivated crop, was undertaken to identify potentially useful populations with low (less than 7% combined) palmitic and stearic fatty acids. Achenes of 86 populations of H. annuus were collected from the central Great Plains of the USA. For each population, a composite sample of 20 achenes was 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 3.9% to 6.5% for the populations. Average stearic acid concentrations ranged from 1.9 to 3.7%. Achene oil of one population of wild H. annuus from Holmquist, SD (ANN-2229, PI 586886) had a palmitic acid level that averaged 3.9%, while stearic acid averaged 1.9%. The combined 5.8% 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 of this population averaged 4.0%, while stearic acid averaged 1.9%. This would indicate that palmitic and stearic acids have a genetic potential for selection. Crossing this population with an inbred cultivated line produced F1 plants with an achene oil that averaged 3.9% palmitic and 2.1% stearic acids. The cultivated inbred parent averaged 6.1% palmitic and 5.1% stearic acids. Achene oil of F2 plants averaged 4.1% palmitic and 1.8 stearic acids, for a total of 5.9%. When F1 plants were backcrossed to the cultivated inbred, palmitic acid averaged 3.8% and stearic acid averaged 1.9% for a total of 5.7%. Preliminary information indicates that palmitic and stearic 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. Other agronomic traits will also need to be monitored during the introgression of the fatty acids genes into cultivated sunflower.