Transgenic Maize

Transgenic maize for commercial production currently confers either insect resistance or herbicide tolerance or a combination of these traits. The introduction of transgenic maize has resulted in an increase in maize production. Effects of these transgenic plants on non-target insects, soil, and animals consuming them have been studied, and in general these effects are small. The economic impact of transgenic maize into the global market has been tremendous because maize can no longer be marketed as a simple commodity. Identity preservation and tracking systems are now required to ensure that maize meets the tolerance levels set by different countries for content of transgenic maize

Seed Quality of Maize Inbred Lines with Different Composition and Genetic Backgrounds

By introgressing exotic germplasm into elite maize in the USA, breeders have developed lines with wider variability for seed oil and protein contents than in U.S. adapted lines. Seed quality of these introgressed lines has not been evaluated. The objectives of the study were (i) to characterize introgressed inbred lines for seed quality, (ii) to assess the effects of oil and protein contents on seed quality, and (iii) to determine whether the interaction between genetic background and production location was significant. The lines used in the study were developed by crossing elite lines of Stiff Stalk and non-Stiff Stalk heterotic background with St. Croix and Argentina germplasm. They were grown at four locations of the U.S. Corn Belt. Seed quality was measured by standard germination test, a series of vigor tests, and an inbred quality index. Genotype × location interactions were significant. Genotypic differences were observed for all the traits measured within each location. Seed composition and genetic background did not affect germination, however production location did. Standard germination ranged from 56 to 93% in Iowa, 48 to 89% in Missouri, 53 to 91% in Illinois, and 52 to 89% in Nebraska. High protein inbred lines had a saturated cold test of 64%, averaged across locations, while the low protein line averaged 49%. Inbred lines with St. Croix background and lines produced in colder locations (Iowa and Nebraska) had high cold test percentage. Inbred lines with St. Croix background, all having low oil contents, had the lowest accelerated aging test results (49%), whereas inbred lines with Argentina background had the highest (65%). The low protein inbred line had low accelerated aging results (49%), whereas high protein inbred lines averaged 62%. Because seed composition affects seed quality of the inbred, it is important that breeders evaluate new germplasm for seed quality early in the breeding program

Improving the fatty acid composition of corn oil by using germplasm introgression

The general public has shown increasing interest in consuming oils that are beneficial to health. Thus, oil from corn (Zea mays L.), along with most major edible oils, has been the target of genetic alterations to improve the fatty acid composition. The fatty acid profile goals vary, depending upon the intended use for the oil. We have targeted the development of corn oil with 1) low total saturated fatty acids, 2) high total saturated fatty acids, and 3) mid-oleic acid, in each case via two different sources: exotic germplasm identified through an international program to broaden the corn germplasm base and introgression of a wild, grassy relative of corn, Tripsacum (Tripsacum dactaloides L). We have been successful at identifying corn lines with each of the noted traits

Thermal and Gelling Properties of Maize Mutants from the OH43 Inbred Line

Starches were isolated from the maize (Zea mays) inbred line Oh43, from its single mutants (amylose extender [ae], brittle-1 [bt1], brittle-2 [bt1], dull-1 [dul], floury-2 [fl2], horny [h], shrunken-2 [sh2], sugary- 1 [sul], and waxy [wx]), and from the double-mutant combinations within Oh43. Differential scanning calorimetry was used to determine the onset temperature (To), range, and enthalpy (DeltaH) of gelatinization and retrogradation, and percentage of retrogradation. The gel strength was measured by using a Voland-Stevens texture analyzer. For gelatinization, the starches of wx dul and sh2 dul had the highest To. Double-mutants ae bt2 and ae dul had the highest To of retrogradation. The highest DeltaH of gelatinization was observed for h wx. The gelatinization enthalpy peak for bt1 starch had a characteristic low temperature shoulder and wide range. Compared with the respective single mutants, most double-mutant combinations had higher To and DeltaH for gelatiniztion and lower To for retrogradation. For gel strength, the dul starch gave the lowest values for firmness and stickiness among the samples. Double mutants generally had gel strength measurements lower than those of the single mutants bt1, bt2, fl2, h, and sh2 but higher than those of dul

Effect of Planting Date on Maize Starch Thermal Properties.

Starches isolated from kernels of two maize (Zea mays L.) inbreds and their F1 progeny, grown after four planting dates, were evaluated for differences in thermal properties. Differential scanning calorimetry (DSC) was used to compare onset (To) and peak (Tp) temperature, range (Rn), and total enthalpy ((Delta)H) values of gelatinization. Amylose content (%AM) of samples was determined colorimetrically, and image analysis was used to determine average diameters of granules. Significant (P less than or equal to 0.05) increases for Tp and (Delta)H were observed with later planting dates. Significant genotypic differences also were seen for To, Tp, and (Delta)H. Later planting dates had no effect on %AM or starch granule size. Genotypes ranked similarly for %AM across each environment, and no differences were observed for average granule diameter. The presence of environmental effects on thermal properties of the starch suggests that if small differences (1-2 C or less than 0.2-0.3 cal/g) are to be identified among nonmutant genotypes, growing conditions may need to be controlled

Altered fatty-acid, protein, oil, and starch corn lines and method for producing same

Improved corn lines having high protein and/or oil content and a method for producing such a lines. In another embodiment, improved corn lines having high oleic fatty-acid content, and/or either elevated or lowered saturated fat content, and a method for producing such a lines. In yet another embodiment, improved corn lines having a starch composition including starch components having a lower peak onset, having lower or higher enthalpy of gelatinization (cal/g), having lower or higher range of gelatinization (° C.), and/or having lower or higher percentage retrogradation. According to the present invention, new genes are introduced from a novel source, viz. Tripsacum dactyloides L., into the Corn-Belt genome or other conventional corn lines and thus the genetic diversity is increased and germplasm and value-added trait enhancement are allowed through traditional plant breeding practices. Introgression merges Tripsacum genetic material into the corn breeding stock. Selection for lines having desired characteristics from the corn lines as well as having improved protein, oil, and/or starch characteristics provides the improved breeding stock of the present invention. In one embodiment, selection is based on near-infrared reflectance measurement of protein, oil, and/or starch of seed. In another embodiment, selection is based on differential scanning calorimetry measurement of starch thermal characteristics. In yet another embodiment, selection is based on gas chromatographic measurement of fatty-acid oil composition of seed. In some embodiments, particular types of fatty acids are selected for in the breeding process

Properties of Sugary-2 Maize Starch: Influence of Exotic Background.

Genetic modifiers of maize (Zea mays L.) starch thermal properties were examined by differential scanning calorimetry (DSC). Sugary- 2 (su2) kernels from segregating ears were identified based on textural appearance of starches following crosses between an exotic maize accession with the inbred OH43 homozygous for the su2 allele (OH43 su2). Two exotic maize accessions, PI213768 and PI451692, were used. Germs retained from su2 kernels were used to produce an F2 population of su2 plants containing 50% exotic germ plasm. With few exceptions, F2 ears from the populations were homozygous for the su2 allele. Significant (P less than or equal to 0.05) differences were seen between the exotic populations and OH43 su2 for gelatinization onset temperature (To), range (RN), enthalpy (deltaH), and retrogradation (%R). The number of DSC values with significant within-population variations was greater among F2 ears within the exotic populations than among ears within the inbred line OH43 su2. Standard deviations for DSC values were consistently greater for exotic su2 populations than for those of OH43 su2. Also, the population PI213768 su2 differed greatly from OH43 su2 for mean values of To, RN, deltaH, and %R (52.8 C, 13.4 C, 1.5 cal/g, and 34.5%, respectively) when compared to those of OH43 su2 (54.6 C, 10.6 C, 1.3 cal/g, and 29%, respectively). Results from this study indicate that examining the texture of starches from single kernels may be used to identify and develop populations homozygous for the su2 allele. In addition, the increased variability for DSC values within populations containing 50% exotic germ plasm suggest that genetic modifiers might be used to alter thermal properties and, possibly, functional properties of su2 starch

Starch-Thickened Acidic Foodstuffs and Method of Preparation

Starch-thickened acidic foodstuffs are provided in which the starch used as a thickener comprises sugary-2 starch obtaining from sugary-2 genotype maize seeds. Sugary-2 starch can be effectively used as a thickener in foodstuffs having a pH of 2.0 to 5.5

Physicochemical Properties of Starches from Mutant Genotypes of the Oh43 Inbred Line.

The physicochemical properties of 17 mutant genotypes of the Oh43 inbred line were investigated to clarify the relationship between structural characteristics and physicochemical properties and among the properties themselves. These physicochemical properties included blue value (BV), maximum absorbance wavelength (lambda[max]), limiting viscosity number ([nu]), swelling power and solubility at 85 C, and percent light transmittance (%T) of starch paste at 650 nm. Pasting properties were determined by means of Brabender viscoamylography, gel strength by texture analysis, and thermal properties by differential scanning calorimetry. Amylose content was the most important structural characteristic affecting the physicochemical properties of starch. Amylose content was significantly (P less than 0.01) correlated with BV (r = 0.96) and lambda(max) (r = 0.81) and was negatively correlated with [nu] (r = -0.83), %T (r = -0.88), swelling power (r = -0.86), and peak viscosity (r = -0.97). Other structural characteristics, including intermediate material content, average chain length of debranched amylopectin, and ratio of long B chains to short B chains plus A chains of amylopectin, were weakly correlated with properties. Some significant correlations were found among properties, including BV, %T, swelling power, and peak viscosity

Genetic Variation for Starch Thermal and Functional Properties Among Nonmutant Maize Inbreds\u27

Differential scanning calorimetry (DSC) has been used in previous \u3c 0.01) inbred by year interaction was present for all DSC parameters studies to detect differences in thermal properties among starches of non- with the exception of AH. Differences were observed in starch viscosities mutant maize (Zea mays L.) genotypes. This study was conducted to and gel strengths for six inbreds selected for highest and lowest Tp, AH, determine the magnitude of genetic and genotype by environmental effects and range (R,). Several significant (P \u3c 0.05) correlations occurred on starch properties among a set of exotic and domestic inbred lines. between DSC parameters and starch paste viscosities and gel strengths. Functional properties of starches from selected lines exhibiting extreme These data suggest that evaluation of starches from nonmutant genotypes DSC values also were investigated. Highly significant (P\u3c 0.01) differences by DSC can be used to predict some functional properties. A practical for DSC starch thermal properties were seen among the lines. Starches application of DSC in breeding programs may include screening maize from exotic lines generally had lower gelatinization onset temperature germplasm for extreme DSC values or population improvement through (TO), peak temperature (Tp), and enthalpy (AH). A highly significant (P recurrent selection. The maize wet-milling industry produces a number of starch- based products important in the food industry. Genetic variability in starch structure and functional properties has led to the use of specialty starches from waxy and high-amylose genotypes (Shannon and Garwood 1984). More recently, the introduction of starches containing double mutant combinations with proper- ties similar to chemically modified starches has resulted in several patents (Katz 1991). The application of differential scanning calorimetry (DSC) to the study of starch was first described by Stevens and Elton (1971). This technique offers a thermodynamic approach to the study of starch gelatinization by monitoring changes in the physical and chemical properties of starches (Donovon et al 1983). Use of DSC in investigating the thermal behavior of starches has become increasingly more popular because it requires only a small sample size and is easy to operate (Sanders et al 1990). Addi- tionally, DSC is relatively rapid compared with more traditional methods of studying starch gelatinization, making it suitable for breeding programs. Extensive variations in DSC parameters have been observed among starches of single- and double-mutant genotypes of maize indicating differences in starch structure and function (Brockett et al 1988, Sanders et al 1990, Wang et al 1992). More recent studies have revealed variations in DSC parameters among non- mutant sources of maize starch. Krueger et al (1987), for example, found differences in DSC parameters among two maize inbred lines and suggested that AH and peak height index (PHI) could be used as a means of identifying maize genotypes. White et al (1990) reported variability in thermal properties by DSC in genetically variable maize populations. The largest differences were observed for gelatinization onset (T.), range (Rn), and total enthalpy (AH). In addition, Li et al (1994) found large variations in DSC values among several exotic populations of maize, sug- gesting that selection among these on the basis of DSC values would identify genotypes having desired starch properties