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921.
922.
Ten parent corn lines, including four mutants (dull sugary2, amylose‐extender sugary2, amylose‐extender dull, and an amylose‐extender with introgressed Guatemalen germplasm [GUAT ae]) and six lines with introgressed exotic germplasm backgrounds, were crossed with each other to create 20 progeny crosses to increase resistant starch (RS) as a dietary fiber in corn starch and to provide materials for thermal evaluation. The resistant starch 2 (RS2) values from the 10 parent lines were 18.3–52.2% and the values from the 20 progeny crosses were 16.6–34.0%. The %RS2 of parents was not additive in the offspring but greater RS2 in parents was correlated to greater RS2 in the progeny crosses (r = 0.63). Differential scanning calorimetry (DSC) measured starch thermal characteristics, revealing positive correlations of peak gelatinization temperature and change in enthalpy with %RS2 (r = 0.65 and r = 0.67, P ≤ 0.05); however, % retrogradation (a measure of RS3) and retrogradation parameters did not correlate with %RS2. The %RS2 and onset temperature increased with the addition of the ae gene, likely because RS delays gelatinization. 相似文献
923.
Katherine M. Phillips David M. Ruggio Mehdi Ashraf‐Khorassani Ronald R. Eitenmiller Sungeun Cho Linda E. Lemar Charles R. Perry Pamela R. Pehrsson Joanne M. Holden 《Cereal Chemistry》2010,87(1):42-49
Twelve popular ready‐to‐eat breakfast cereals fortified with folic acid were sampled in the United States in 2006, and the data have been incorporated into the USDA National Nutrient Database for Standard Reference. Cereals were collected from three statistically selected retail outlets in each of four primary census regions, and four composites of each product were prepared using random groupings of three locations each. Folic acid was determined using a validated LC‐MS method, with 13C‐folic acid as an internal standard, after trienzyme treatment and solid phase extraction. A cereal reference material (AACC VMA399) was analyzed as a control. Selected samples were also assayed using the standard microbiological method, with and without trienzyme extraction, to generate an estimate of endogenous folate. On average, as shown on the label, folate content was underestimated. In seven cereals, folate was within 5% of the declared value; in four cereals, it was 5–20% higher; and in two cereals, it was >20% greater, representing –75 to +69 μg/serving (mean 17) of the label value, equivalent to –19% to +17% of the 400 μg/daily value. The microbiologically determined folic acid was higher than LC‐MS by 10–67% (mean 40%). Therefore, use of label values might underestimate folate intake from some breakfast cereals. 相似文献
924.
Linda D. Highfield Michael P. Ward Shawn W. Laffan Bo Norby Gale Wagner 《Veterinary research》2009,40(3)
Modeling potential disease spread in wildlife populations is important for predicting, responding to and recovering from a foreign animal disease incursion such as foot and mouth disease (FMD). We conducted a series of simulation experiments to determine how seasonal estimates of the spatial distribution of white-tailed deer impact the predicted magnitude and distribution of potential FMD outbreaks. Outbreaks were simulated in a study area comprising two distinct ecoregions in South Texas, USA, using a susceptible-latent-infectious-resistant geographic automata model (Sirca). Seasonal deer distributions were estimated by spatial autoregressive lag models and the normalized difference vegetation index. Significant (P < 0.0001) differences in both the median predicted number of deer infected and number of herds infected were found both between seasons and between ecoregions. Larger outbreaks occurred in winter within the higher deer-density ecoregion, whereas larger outbreaks occurred in summer and fall within the lower deer-density ecoregion. Results of this simulation study suggest that the outcome of an FMD incursion in a population of wildlife would depend on the density of the population infected and when during the year the incursion occurs. It is likely that such effects would be seen for FMD incursions in other regions and countries, and for other diseases, in cases in which a potential wildlife reservoir exists. Study findings indicate that the design of a mitigation strategy needs to take into account population and seasonal characteristics. 相似文献
925.
Evolution of a microbial acetyltransferase for modification of glyphosate: a novel tolerance strategy 总被引:6,自引:0,他引:6
Siehl DL Castle LA Gorton R Chen YH Bertain S Cho HJ Keenan R Liu D Lassner MW 《Pest management science》2005,61(3):235-240
N-Acetylation is a modification of glyphosate that could potentially be used in transgenic crops, given a suitable acetyltransferase. Weak enzymatic activity (k(cat) = 5 min(-1), K(M) = 1 mM) for N-acetylation of glyphosate was discovered in several strains of Bacillus licheniformis (Weigmann) Chester by screening a microbial collection with a mass spectrometric assay. The parental enzyme conferred no tolerance to glyphosate in any host when expressed as a transgene. Eleven iterations of DNA shuffling resulted in a 7000-fold improvement in catalytic efficiency (k(cat)/K(M)), sufficient for conferring robust tolerance to field rates of glyphosate in transgenic tobacco and maize. In terms of k(cat)/K(M), the native enzyme exhibited weak activity (4-450% of that with glyphosate) with seven of the common amino acids. Evolution of the enzyme towards an improved k(cat)/K(M) for glyphosate resulted in increased activity toward aspartate (40-fold improved k(cat)), but activity with serine and phosphoserine almost completely vanished. No activity was observed among a broad sampling of nucleotides and antibiotics. Improved catalysis with glyphosate coincided with increased thermal stability. 相似文献
926.
Oswaldo Taboada‐Gaytan Linda M. Pollak Lawrence A. Johnson Steven R. Fox Kevin T. Montgomery 《Cereal Chemistry》2010,87(3):175-181
Hybrids with high grain yield and higher starch, protein, or oil content are available to corn growers; however, they result from crossing adapted Corn Belt inbred lines that rarely include exotic germplasm. This study was conducted to determine whether Corn Belt lines introgressed with exotic materials from Argentina, Chile, Uruguay, Cuba, and Florida have appropriate wet‐milling characteristics in their hybrids. Ten lines from the Germplasm Enhancement of Maize (GEM) project with different starch contents were crossed to three adapted inbred lines used as testers. The B73×Mo17 hybrid was used as a control. The F1 generation of these 30 experimental hybrids was analyzed using both near‐infrared transmittance (NIT) technology and a 100‐g modified wet‐milling procedure, and measuring test and 1,000‐kernel weight. There was great variation among physical, compositional, and wet‐milling characteristics of the experimental hybrids, suggesting that exotic germplasm can be used to improve wet‐milling characteristics of Corn Belt hybrids. 相似文献