Author
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Seiler, Gerald |
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Submitted to: International Sunflower Association Sunflower Yearbook
Publication Type: Proceedings Publication Acceptance Date: 6/30/2002 Publication Date: N/A Citation: N/A Interpretive Summary: The sunflower (Helianthus) consists of 50 species, 14 annual and 36 perennial and 19 subspecies and is one of the few native crops of North America. Having the wild relatives of the crop available within the boundaries of the USA has facilitated the collection of wild sunflower germplasm. Ten explorations covering the USA and Canada have been undertaken since 1980. It is the largest and most complete wild sunflower collection in the world having representative populations of all extant species. Germplasm from the wild sunflower collection has been used extensively to diversify the genetics of sunflower to make it an adaptable, viable, and sustainable crop. Cultivated hybrid sunflower production depends on a single male-sterile cytoplasm (French PET1) and a few fertility restoration genes. This narrows the genetic base putting the crop in a potentially dangerous position in terms of genetic vulnerability. The wild species have served as a source for new fertility restoration genes for the PET1 cytoplasm. It was not known whether the fertility restoration genes from the wild species for the commonly used cytoplasm were different from the ones used in many commercial hybrids. After testing, it appears likely that the restoration gene(s) of the eight wild sunflower accessions are at the same locus as the common restoration genes. The restoration genes from the eight wild sunflower accessions are likely to be alleles of the commonly used genes. A further study to compare these genes is needed. 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 survey of wild sunflower species, 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. Achene oil of one population of wild H. annuus from Holmquist, SD had a palmitic acid concentration of 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. Also achene oil of one population of wild H. giganteus (GIG-102) from INRA, Montpellier, France, had a palmitic acid level that averaged 47 g kg-1, while stearic acid averaged 18 g kg-1. The combined 65 g kg-1 palmitic and stearic acids is 40% lower than the present level of these fats in sunflower oil. The level of saturated fatty acids observed in the populations remained low when plants were grown in the greenhouse under uniform conditions. Preliminary information indicates that introducing genes from populations of wild ancestors into cultivated sunflower can reduce palmitic and stearic acids in sunflower oil. Further research will be needed to determine the inheritance of these fatty acids. Other agronomic traits will need to be monitored during the introgression of the fatty acids genes into cultivated sunflower. Technical Abstract: Sunflower (Helianthus annuus L.) is one of a few native crops of North America. Since the establishment of the wild sunflower germplasm collection in 1976, over 2200 accessions have been added to the collection, which is located at the USDA-ARS, North Central Regional Plant Introduction Station at Ames, Iowa. It is the largest and most complete wild sunflower collection in the world having representative populations of all extant species. Wild species are the source of the male sterile cytoplasm used in most all commercial hybrids, and of several resistance genes for prevalent sunflower pathogens. Germplasm from the wild sunflower collection has been used extensively to diversify the genetics of sunflower to make it an adaptable, viable, and sustainable crop. Cultivated hybrid sunflower production depends on a single male-sterile cytoplasm (French PET1) and a few fertility restoration genes. This narrows the genetic base putting the crop in a potentially dangerous position in terms of genetic vulnerability. The wild species have served as a source for new fertility restoration genes for the PET1 cytoplasm. It was not known whether the fertility restoration genes from the wild species for the PET1 cytoplasm are different from the commonly used Rf1 gene. Half-diallel progenies of crosses of RHA 274 with the wild species lines did not segregate for fertility restoration, except for crosses with Rf ANN-1742 and Rf ANN-1064. Non-segregation indicates that the restoration genes are at the same locus as the commonly used Rf1 gene in RHA 274. It is therefore likely that the restoration gene(s) of these lines are at the same locus as the Rf1 gene. The restoration genes from the eight wild sunflower accessions are likely to be alleles of the Rf1 gene. Further studies to compare them with the Rf1 gene are needed. In recent years consumers have become concerned about the consumption of saturated fats in their diet. Edible oils are the principal source of fats in many diets. Sunflower oil contains 11 % saturated palmitic and stearic acids. This is considered a moderate concentration. A reduction of the saturated fatty acids to the 6 to 7% concentration would enhance the acceptability of sunflower oil as a healthier edible oil. A population of wild H. annuus from Holmquist, SD (PI 586886) had an average palmitic acid concentration of 3.9%, and an average stearic acid concentration of 1.9%, totaling 5.9%. This concentration is approximately 45% less than typically observed in commercial sunflower. When plants were grown in a greenhouse, oil of the plants averaged 4% palmitic and 1.9% stearic, similar to the values observed in the original population indicating the trait's stability. Palmitic acid concentration for oil of interspecific F1, F2, and BC1F2 plants averaged 3.9, 4.1, and 3.8%, respectively, while stearic acid averaged 2.1, 1.8, and 1.9%, respectively. Achene oil of one population of wild perennial H. giganteus (GIG-102) from INRA, Montpellier, France, had a palmitic acid level that averaged 47 g kg-1, while stearic acid averaged 18 g kg-1. The combined 65 g kg-1 palmitic and stearic acids is 40% lower than the present level of these fats 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 averaged 48 g kg-1, while stearic acid averaged 16 g kg-1. Crossing this population with an inbred cultivated line produced F1 plants with achene oil that averaged 39 g kg-1 palmitic and 26 g kg-1 stearic acid. The inbred cultivated parent averaged 55 g kg-1 palmitic and 51 g kg-1 stearic acid. F2 plants produced achene oil that averaged 47 g kg-1 palmitic and 29 g kg-1 stearic acid, for a total of 76 g kg-1. When F1 plants were backcrossed to the cultivated inbred, BC1F1 plants produced achene oil that aver |
