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a Mississippi State Univ., North Mississippi Research and Extension Center, 5421 Highway 145 South, P.O. Box 1690, Verona, MS 38879
b Sunflower Research Unit, USDA-ARS, 1307 N 18TH ST, Northern Crop Science Lab., Fargo, ND 58105
c Delta Research and Extension Center, P.O. Box 197, Stoneville, MS 38776
d Dep. of Plant and Soil Sci., Dorman Hall, Mississippi State Univ., MS 39762
e Dep. of Engineering, Nova Scotia Agricultural College, 50 Pictou Road, P.O. Box 550, Truro NS B2N 5E3 Canada
* Corresponding author (vj40{at}pss.msstate.edu).
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ABSTRACT |
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 TOPNOTES ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Abbreviations: ICAP, inductively coupled argon plasma spectrometer • LET, low energy technology • PPI, preplant incorporated
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TOPNOTESABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Received for publication July 24, 2007.
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INTRODUCTION |
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TOPNOTESABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Sunflower oil has a wide range of applications, such as in the food industry, in commercial products, or in biodiesel production (Arkansas Biofuel Enterprises, 2007; National Sunflower Association, 2007). The fatty acid composition of vegetable oils influences their functional and nutritional properties (Warner et al., 2003; Burton et al., 2004) and determines their uses. The fatty acid composition of sunflower oil depends on genetic and environmental conditions (Robertson et al., 1978; Lajara et al., 1990; Miller and Vick, 1999; Sobrino et al., 2003). Sunflower seed contain up to 90% unsaturated fatty acids (combined oleic and linoleic), and approximately 10% saturated fatty acids (palmitic and stearic) (Steer and Seiler, 1990). Depending on fatty acid composition, sunflower can be divided into traditional sunflower with oleic acid content of 14 to 39% of the oil, mid-oleic acid sunflower (42–72% oleic acid content, also called NuSun, Mycogen, Breckenridge, MN, in the United States), and high-oleic acid sunflower (75–91% oleic acid) (Codex Alimentarius Committee, 2005). Consumers value mid-oleic and high-oleic acid sunflower because of their proven health benefits (Jing et al., 1997; Krajcovicova-Kudlackova et al., 1997; Hu et al., 2001). Hence, breeders have recently developed several mid- and high-oleic acid sunflower hybrids (Hardin, 1998; Kleingartner, 2002; Burton et al., 2004). Oleic acid and saturated fatty acids are desirable in frying, because unlike polyunsaturated fatty acids, they do not need to be hydrogenated. High- and mid-oleic sunflower oils are heart-healthy, with high stability in frying applications, and have a long shelf life, which makes the oil a valuable all-purpose commodity for the nearly 3 billion kg per year market of frying oils (Warner et al., 2003).
Although sunflower oil is known mainly as an edible oil for human nutrition, it can also be used for biodiesel production. Biodiesel is one of the renewable fuels that is produced mainly from soybean [Glycine max(L.) Merr.], canola (Brassica sp.), sunflower, and other oilseed crops (National Sunflower Association, 2007). According to the USDA, biodiesel offers environmental, economic, and national security benefits (National Sustainable Agriculture Information Service, 2007). With the acceptance of biodiesel as a replacement for petroleum-based fuel, growers in the southeastern United States have been looking for an opportunity to tap into this rapidly expanding market. The U.S. biodiesel demand increased by more than 400 times from 1999 to 2006 (National Sunflower Association, 2007). Most areas in Mississippi have spring-planted row crops, with significant expertise and equipment for growing the row crops. Sunflower has been shown to fit well into cereal-based rotations (Halvorson et al., 1999). Sunflower for biodiesel production was evaluated earlier in Florida within the low energy technology (LET) concept (Green et al., 1980, 1981, 1982) but has not been explored in Mississippi.
There is potential for sunflower (for production of cooking oil or biodiesel) to fit into some of the traditional cropping systems and subsequently to improve economic sustainability of agriculture in Mississippi. There is insufficient research on the effect of N and cultivar in the southern states with respect to productivity, oil content, and fatty acid profile of sunflower oil. No research on these characteristics has been reported for Mississippi conditions. Our hypothesis was that sunflower can be grown under Mississippi environmental conditions for cooking oil or biodiesel production, and both N rates and hybrids will have an effect on seed yield, oil content, and fatty acid composition. The objective of the research was to evaluate the effect of N, hybrid, and their interaction on yield, oil content, and composition of sunflower seed at five locations in Mississippi.
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MATERIALS AND METHODS |
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TOPNOTESABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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The fatty acid composition of the seed oil of the four hybrids resulted from the influence of both the hybrid genotype and the environment of the hybrid seed production fields in Woodland, CA. Five locations (Fig. 1 ) were chosen to represent major growing areas and different soil types of Mississippi (Table 1 ). All five sites had different soil types (Table 1) (U.S. Department of Agriculture, Soil Survey Division, Natural Resources Conservation Services, 2001).
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The previous crop at each of the five locations was different: fallow in Newton, corn in Stoneville and Verona 1, soybean in Starkville, and perennial grass in Verona 2 locations. Soil tillage was as traditional for row crops in the region and included disking and formation of raised beds at 97 to 102 cm center to center at the beginning of April. The raised beds are typically used for row crops in the region to improve surface drainage. Weed control at all locations was conducted by using preplant incorporated (PPI) herbicide Treflan (DowAgroSciences, Zionsville, IN; trifluralin: 
,,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 4.5 to 5.6 kg ha–1, depending on soil type. The herbicide was applied after the initial formation of the raised beds, and then carefully incorporated. Seeding was accomplished with a cone planter at 3.8 cm depth, at 97 to 102 cm interrow space, and a seeding rate to provide 6.4 seed m–1 of row. Because of differences in seed size among the hybrids, seeding rate (by weight) was different for each hybrid, but was the same for a particular hybrid at every location. Seeding rates for the hybrids DKF2990, DKF3510, DKF3875, and DKF3901 were 3.47, 5.12, 4.37, and 4.13 kg ha–1, respectively. Plots were 6 by 4 m, with four rows in every plot.
Nitrogen [as urea-ammonium nitrate solution (UAN) 32% N] was knifed in on either side of the row (20–25 cm from row) and was applied in 67 kg ha–1 increments: the first 67 kg increment in the 67, 134, and 202 kg ha–1 N treatments was applied at the seeding stage; the second application (in the 134 and 202 kg ha–1 N treatment) was applied a month later in V-4, R-1 stage (Schneiter and Miller, 1981), and a third application (in the 202 kg ha–1 treatments) a month later after the second application in R-2 stage (Schneiter and Miller, 1981). With respect to diseases, head rot (Rhizopus sp.) was identified; however, the incidence was very low and did not warrant any treatments. Blackbirds (Agelaius phoeniceus L.) proved to be a major pest factor. For control of blackbirds, propane cannons were used. Also, stem weevil (Cylindrocopturus adspersus LeConte) and head clipping weevil (Haplorhynchites aeneus Boh.) infestation was found at the two Verona locations only. Hence, sunflower at Verona was treated with Sevin (80% carbaryl, Lesco, Inc., Tjroy, MI) at 1.4 kg ha–1. Harvesting commenced when all plants reached harvesting maturity, after physiological stage R-9 (Schneiter and Miller, 1981), and was accomplished by harvesting the two inner rows in each plot. Threshing was done using a stationary thresher (Almaco, LPR-E, Nevada, IA), seed moisture was determined using a stationary electronic grain-moisture tester (Model GAC2000, Dickey-John, Auburn, IL) in a 500-g sample from each plot. Seed subsamples (around 100 g) from each plot at the five locations were further cleaned by hand to remove any occasional broken seed or impurities, put immediately in a freezer at –20°C for 24 h to prevent disease development and kill insects, and then stored in a refrigerator at 4°C until further analysis.
Fatty Acid Composition Analysis
Each sample of clean and unbroken seed was ground in a Krupps coffee grinder and a portion (0.15–0.25 g) was added to a 13 x 100 mm disposable culture tube. Three milliliters of a solution of hexane-chloroform-0.5 M sodium methoxide in methanol (Sigma, St. Louis, MO) (75:20:5, v/v/v) was added to the tube and the mixture was vortexed for 2 to 5 s. The mixture was settled for 10 min and the upper clear portion was transferred to a vial. The vial was capped and the sample was injected into a Hewlett-Packard Model 5890 gas chromatograph containing a DB-23 capillary column (30 m x 0.25 mm, J&W Scientific, Folsom, CA), which was held at 190°C for 4 min, then increased to 220°C at 15°C/min, held at 220°C for 1 min, then increased to 240°C at 25°C/min, and finally held at 240°C for 1.0 min, for a total run time of 8.8 min. Fatty acid concentrations are expressed as percent by weight of the total fatty acids.
Oil Content Analysis
Oil content of the seed was determined using a 40-mL sample of cleaned, weighed seed using a Maran Ultra Resonance NMR instrument (Resonance Instruments Ltd., Witney, UK), following the American Oil Chemists' Society Official Methods and Recommended Practices, AK4–95 (American Oil Chemists' Society, 1994). Because seeds from different hybrids had various moisture contents, oil contents were adjusted to 0% moisture content.
Statistical Methods
For each of the five locations, the design was two-factor factorial in four blocks for yield response, and in three blocks for the fatty acid composition responses. The factors of interest: hybrid with four levels (DKF3875, DKF2990, DKF3510, and DKF3901) and N application rate with four levels (0, 67, 134, and 202 kg ha–1) were treated as fixed. Block effect was treated as random in the Mixed procedure of SAS (SAS Institute Inc., 1999). Since the fatty acid compositions for the different hybrids of the original certified seed were not uniform (Table 2
), the corrected fatty acid composition responses calculated as the difference between the measured and the original were analyzed. The implication of this correction is: if a treatment mean is positive, then the treatment increases the composition; and if it is negative, then the treatment decreases the composition. For each response and within each location, the residuals were examined to verify normal distribution and constant variance assumption of the error terms as described in Montgomery (2005).
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RESULTS AND DISCUSSION |
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TOPNOTESABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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Main and Interaction Effects of Hybrid and Nitrogen on Measured Responses
Statistical analyses indicated that the interaction effect of hybrid and N rate was significant on seed yield at the Verona 1 and Starkville (marginally) locations suggesting that at these locations, effectiveness of N application depends on the hybrid (Table 3
). At the Stoneville, Newton (marginally), and Verona 2 (marginally) locations, the main effect of hybrid was significant on yields, whereas the main effect of N rate was significant at Stoneville only (Table 3).
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Concentration of one of the main fatty acids, oleic, was significantly affected by hybrid at all locations. In addition, oleic acid was marginally affected by N rate at the Verona 2 location. With the exception of the Verona 2 location (where there was a marginally significant interaction between hybrid and N rate), hybrid was the major modifier of linoleic acid, the other major acid in sunflower oil (Table 3).
Hybrid and N rate were significant with respect to oil concentration (corrected for 0% seed moisture) at Stoneville, Newton, and the Verona 2 location, but only the main effect of hybrid was significant on oil content at the Verona 1 location (Table 3). These results confirm the general understanding that both genotype and environment are major modifiers of seed oil content of sunflower (Leon et al., 2003).
Effect of Hybrid on Seed Yields in Different Locations
At Stoneville, DKF3510 provided higher seed yields compared to DKF3901 or DKF2990 (Table 4
). However, DKF3875 yielded similarly to DKF3510 and to DKF3901. At Newton, higher yields were provided by DKF3510 with lower yields from DKF3901 and DKF3875, whereas yields from DKF2990 were not different from the other hybrids. At the Verona 2 location, DKF3901 provided greater yields compared to DKF2990, while yields from the other two hybrids were not significantly different from DKF3901 or DKF2990. The above results suggest that genotypes (hybrids) can express differential comparative productivity depending on the local environment conditions and soil properties (Table 1).
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Oleic Acid
With the exception of one hybrid at one location (DKF3510 at the Verona 2 location), the concentration of oleic acid in all hybrids at all five locations increased relative to the oleic acid concentration in the original certified seed (Table 4 and Table 2). This increase in oleic acid actually "transformed" traditional sunflower hybrids DKF3875, DKF2990, and DKF3901 into mid-oleic acid sunflower (Codex Alimentarius Committee, 2005) or even into NuSun (National Sunflower Association, 2007), which is a significant finding. Overall, the increase in oleic acid concentration relative to the original seed depended on the hybrid: the lower the oleic acid concentration in the original seed, the higher was the increase for oleic acid concentration. Hence, a higher increase in oleic acid was found in DKF2990, lower in DKF3875, even lower in DKF3901 and lowest in DKF3510.
Linoleic Acid
Overall, the linoleic acid decreased relative to the respective concentrations in the original seed (Table 4 and Table 2). However, this reduction depended on hybrid; and at all locations, whenever there was an increase in the oleic acid concentration, there was a corresponding decrease in linoleic acid concentration.
Our results indicate that genotype (hybrid) determined the concentration of the main fatty acids in sunflower oil, oleic and linoleic. Indeed, previous research demonstrated that the fatty acid profile of sunflower oil is genetically controlled (Burton et al., 2004). In general, our results also support earlier studies that found a strong influence of environmental conditions on oil profile (Robertson et al., 1978). However, this is the first study to demonstrate such a dramatic increase in oleic acid content of sunflowers relative to the original seed.
Seed Oil
Seed oil concentration in this study was generally high and similar to previous reports (de la Vega and Hall, 2002,; National Sunflower Assocation, 2007). Seed oil concentration is important for growers and processors. For example, currently, sunflower crushing plants in North Dakota and in Kansas offer 2% price premium for every 1% oil above 40% (National Sunflower Assocation, 2007). At the Stoneville and Verona 2 locations, DKF2990 and DKF3875 contained a greater amount of oil compared to the other two hybrids (Table 4). However, at Newton, oil content was higher in DKF2990, less in DKF3510 and DKF3901, and least in DKF3875. Oil content at Verona 1 was highest in DKF2990, less in DKF3875, lower in DKF3901 and lowest in DKF3510 (Table 4). The above results suggest that sunflower seed oil concentration depends on genotype (hybrid), but it may be expressed differentially under different environments.
Effect of N on Seed Yields, Oil Content, and Fatty Acid Composition
At Stoneville, seed yields were increased with increased N rates at 67 to 202 kg ha–1 (Table 5
). At Stoneville, Newton, and Verona 2 locations, increasing N rates tended to decrease the reduction in the concentration of stearic acid relative to the original seed (Table 5). However, the reduction was not significantly different for 67 to 202 kg ha–1 N rates. Unlike at the other locations, the application of N at a higher rate significantly increased oleic acid at the Verona 2 location.
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The above results suggest that genotypes react differently to the environmental conditions in different areas of Mississippi with respect to oleic and linoleic acid concentration, and fatty acid composition in general. Sunflowers grown in Mississippi would generally increase the accumulation of oleic acid of traditional sunflower and "transform" them into mid-oleic acid or NuSun hybrids (National Sunflower Association, 2007). This may improve marketability of sunflower seed oil produced in Mississippi because consumers value high-oleic acid sunflower seed. Reducing the concentration of saturated fatty acids in vegetable oils is preferred by consumers and has promoted breeding programs for low stearic and palmitic acid sunflower (Burton et al., 2004; Miller and Vick, 1999). As expected, the increase in oleic acid causes a corresponding reduction in the accumulation of linoleic acid in sunflower oil. The increase in oleic acid from north to south latitude and the corresponding reverse trend in linoleic acid has been reported by Robertson et al. (1978). The same authors found that latitude had limited effect on saturated fatty acid concentration in sunflower oil. Similar results on the effect of climatic conditions and latitude on linoleic acid were reported by Lajara et al. (1990). Sobrino et al. (2003) developed models to explain and predict oleic acid concentration in sunflower oil as a function of geographic and climatic conditions. They reported temperature during development and maturation of sunflower achenes is one of the most important factors for production of oleic acid. Izquierdo et al. (2006) also developed a model for predicting fatty acid composition in sunflower. They found that during the 100 to 300 degree-days (above 6°C) after flowering, the minimum night temperatures accounted for most of the variability of oleic acid concentration.
Interaction Plots
Interaction plots of hybrid by N application rate revealed that at the Starkville location, N rates at 202 kg ha–1 increased yields from DKF3510, but did not affect yields for DKF3875 or DKF2990 (Fig. 2
). Nitrogen at 67 and 134 kg ha–1 rates decreased yields of DKF3901. Yields at 202 kg ha–1 increased relative to the 67 kg ha–1 N rate, but were not different from the 0 kg ha–1 or the 134 kg ha–1 rates. At the Verona 1 location, N application in general increased yields in all hybrids (Fig. 2). Yields from DKF3875 and DKF3510 increased correspondingly in the 67 rate and then in the 134 kg ha–1 N rates, but further N increase did not result in a corresponding yield increase. For DKF2990, higher yields were achieved in the 67 kg ha–1 rate, but further N increase did not bring a corresponding yield increase. It has been demonstrated that sunflower is a good N scavenger and may require relatively low N fertilizer application rates (34 kg N ha–1) to provide good yields (Halvorson et al., 1999). Hence, in some countries sunflower is grown with no addition of fertilizers (Mercau et al., 2001; Ruiz and Maddonni, 2006). Seed yields at the Verona 1 location were high and similar to sunflower yields reported in the literature (Halvorson et al., 1999; de la Vega and Hall, 2002). Overall, seed yields in this study at four of the locations were similar or much exceeded the average sunflower yields in the United States for the 2001–2006 period, which varied between 1280 and 1750 kg ha–1 (National Sunflower Association, 2007).
At Stoneville, N at 134 and 202 kg ha–1 increased the concentration of palmitic acid in DKF3901, but not in other hybrids (Fig. 3 ). At Starkville, increased N rates did not change palmitic acid concentration in oil (Fig. 3). At the Verona 1 location, N rates at 134 and 202 kg ha–1 increased palmitic acid in the oil of DKF3875, and N rate at 202 decreased palmitic acid in DKF2990 relative to the 0 kg N ha–1. However, at the Verona 2 location, N rates at 134 and 202 kg ha–1 decreased palmitic acid in the oil of DKF3875 relative to the 0 kg N ha–1. Also in DKF2990, N at 202 kg ha–1 decreased palmitic acid relative to the 0 kg N ha–1 treatment (Fig. 3).
At the Verona 1 location, N at 202 kg ha–1 reduced stearic acid in DKF3875 relative to the 0 kg N ha–1 and the 67 kg N ha–1 rates (Fig. 4 ). Nitrogen at 67 and 134, but not at 202 kg N ha–1 rate, reduced stearic acid in DKF3901. Furthermore, N at 67 kg ha–1 decreased stearic acid in DKF2990 relative to the 0 kg ha–1 rates. At the Verona 2 location, N at 134 and 202 kg ha–1 rates reduced linoleic acid in DKF3875 and DKF2990 relative to the respective 0 kg ha–1 N rate (Fig. 4).
CONCLUSION
Overall, this study demonstrated sunflower could be a viable crop in Mississippi with yields comparable to other regions of the United States. Generally, increasing N rates reduced seed oil concentration but increased seed yields and subsequently oil yield per area. In most cases, N rate, hybrid, or N by hybrid interaction resulted in altered fatty acid profile of sunflower oil compared to the composition of the planted seed, with the effects being different at the different locations. Overall, fatty acid composition depended mainly on genotype (hybrid). Increased N application rates increased oleic acid concentration of the four hybrids in the Verona 2 location and decreased stearic acid concentration in the Stoneville, Newton, and Verona 2 locations.
The increase in oleic acid content in sunflower grown in Mississippi (relative to the original seed) could be used as a marketing tool, because oleic acid has been shown to have nutritional benefits and to reduce coronary heart disease (Jing et al., 1997; Krajcovicova-Kudlackova et al., 1997; Hu et al., 2001). The U.S. Department of Agriculture dietary recommendations call for a reduction of saturated fatty acids by the American consumer (U.S. Department of Agriculture, Human Nutrition Information Service, 1992). Also, high-oleic acid sunflower oil does not need to be hydrogenated when used as a frying oil, which offers significant advantages over the use of other vegetable oils such as soybean, canola, and traditional low-oleic acid sunflower (Kleingartner, 2002; National Sunflower Association, 2007). Although linoleic acid is valuable for the paint industry and has also been recognized to have health benefits, it may be less important than high-oleic acid, since other less expensive vegetable oils [soybean and corn (Zea mays L.)] are also high in linoleic acid and have an established status on the American market (Kleingartner, 2002). Hence, the high-oleic acid of sunflower oil translates into improved health and frying advantages. Our preliminary data demonstrated that sunflower production in Mississippi and possibly in other southern states is feasible. Sunflower could be grown as an oilseed or biodiesel crop in Mississippi and possibly for the health market. Further research is needed to establish the best management practices for sunflower in Mississippi and to evaluate sunflower in rotation with other field crops in the region.
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ACKNOWLEDGMENTS |
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REFERENCES |
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TOPNOTESABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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arkansasbiofuels/id33.html (accessed April 2007; verified 7 Mar. 2008).This article has been cited by other articles:
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  V. D. Zheljazkov, B. A. Vick, B. S. Baldwin, N. Buehring, T. Astatkie, and B. Johnson Oil Content and Saturated Fatty Acids in Sunflower as a Function of Planting Date, Nitrogen Rate, and Hybrid Agron. J., July 7, 2009; 101(4): 1003 - 1011. [Abstract] [Full Text] [PDF]
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