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The seed vigor of a super-sweet mutant of sweet corn (Sweetie 76) was compared to that of a traditional, non-mutant variety (Jubilee). The inherent seed vigor of a typical super-sweet corn mutant was considerably less than that of a traditional non-mutant variety. Leakage of reducing sugars from sweet corn seeds at a low temperature was not correlated with seed vigor.

Thesis (M.S.)--University of Kentucky, 2000. / Title from document title page. Document formatted into pages; contains viii, 52 p. : ill. Includes abstract. Includes bibliographical references (p. 47-51).

Three varieties of sweet corn (Zea mays L.) , including two supersweet (Crisp 'N Sweet 710 and Rogers 3376) and one normal sweet (Jubilee), were harvested at six stages of maturity (80-72% moisture for supersweet and 75-68% moisture for normal sweet) at three days intervals. Changes in physical and chemical properties over the 15 day harvest period and effects of steam blanching on carbohydrate composition of both genotypes of sweet corn were determined. Moisture content of the kernels decreased with maturity. A quick microwave oven moisture method for determining moisture content of normal sweet and supersweet corn was evaluated and found to be a good alternative method for the time-consuming standard AOAC vacuum oven method. Yield (as represented by average ear weight) increased linearly with maturity. Percent soluble solids was determined to be a satisfactory maturity index for normal sweet corn but not for supersweet corn. The pericarp content in the normal sweet corn Jubilee increased 25% over the 15-day harvest period compared to a mean of 5-6% in the supersweet varieties. Values of the shear press tests were not significantly correlated to % moisture, and only values of compression work showed a positive trend to increase with maturity. Total sugars of supersweet corn averaged 2-3 times higher and decreased more slowly than those of normal sweet corn in the comparable maturity range for processing. Sucrose was the major sugar in both corn genotypes and represented about 80% of the total sugars (9-20% dry weight) in normal sweet corn versus 90% of the total sugars (30-45%) in supersweet corn. Polysaccharides consisted mainly of starch in supersweet corn and of water soluble polysaccharide (WSP) in normal sweet corn. Normal sweet corn contained about twice as much polysaccharides as did supersweet corn. Percent total polysaccharides increased with maturity. Although higher in sugars, supersweet corn had lower % total carbohydrates than normal sweet corn due to its low polysaccharide content. Blanching of corn-on-the-cob for 10 minutes in 99°C steam resulted in a significant loss of sugars. Blanching did not significantly reduce total polysaccharides of sweet corn. / Graduation date: 1990

Thesis (Ph. D.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

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The effect of different blanching treatments and packaging materials on the enzymatic (lipoxygenase and peroxidase) activity and fatty acid stability of two different varieties of sweet corn on the cob (Jubilee and GH 2684) was evaluated during nine months of frozen storage at -23.3°C. The initial moisture content in the kernels of the two sweet corn varieties averaged 72.5%. After nine months of frozen storage the moisture content in the kernels of corn depended greatly on the packaging material used. The ears stored in Cryovac B and E bags showed the best moisture retention (72.2% final moisture content), followed by the polyethylene bags (71.4%) while the ears stored without packaging material showed severe dehydration (70.1%). The peroxidase and lipoxygenase activities were determined using spectrophotometric assays on a crude extract obtained from liquid nitrogen powdered corn. Both unblanched varieties of sweet corn showed similar initial peroxidase specific activity and general behavior during the nine months of frozen storage. The presence of lipoxygenase isozymes with different thermal stabilities in both varieties was suggested by the higher lipoxygenase specific activity found in Jubilee after freezing and nine months of frozen storage (0.135 units/mg protein) compared with the GH 2684 variety (0.115 units/mg protein). Complete inactivation of lipoxygenase was obtained after 9 minutes steam blanching at 100°C. Peroxidase was more heat resistant showing some remaining specific activity after 9 minutes steam blanching with a complete inactivation after 15 minutes steam blanching. No regeneration of either enzyme was observed during the nine months of frozen storage suggesting a permanent disruption of the active site of both enzymes. Relative fatty acid content was determined by gas chromatographic analysis of fatty acids methyl esters. The major fatty acids present in both varieties were palmitic (14.93%), stearic (2.79%), oleic (31.54%), linoleic (46.87%) and linolenic (1.89%) acids. Good stability of the polyunsaturated fatty acids was observed during the nine months storage at -23.3°C, with autoxidation as the main mechanism responsible for the decrease in the relative percent of polyunsaturated fatty acids. Some enzymatic oxidation also occurred, decreasing the linolenic acid content. The control of the degradation of polyunsaturated fatty acids depended mostly on the frozen storage temperature (-23.3°C) and not on the oxygen permeability of the different packaging materials. The results obtained in our study suggested that blanching of the ears of sweet corn had an important effect on reducing the enzyme activity but little effect on the polyunsaturated fatty acid degradation after 9 months of storage at -23.3°C. / Graduation date: 1994

Coleomegilla maculata is a beneficial coccinellid commonly found in sweet cornfields in Kentucky. Previous work on C. maculata has shown an ovipositional preferencefor the weed Acalypha ostryaefolia, compared to three selected weed species and corn. Also, predation of C. maculata egg clusters on A. ostryaefolia was less compared toclusters on corn and the presence of A. ostryaefolia led to higher densities of C. maculata larvae on corn. I determined C. maculata ovipositional preference among weed species in fieldtests using nine common weeds. I also examined ovipositional preference using just A.ostryaefolia and Abutilon theophrasti. I assessed the roles of potential prey densities,plant structures, and weed attractiveness to adult C. maculata. Finally, I examineddiurnal and nocturnal predation of C. maculata eggs on corn, A. ostryaefolia, A.theophrasti, and Amaranthus hybridus. Significant ovipositional preference was always observed for A. theophrasti. C. maculata egg clusters on A. theophrasti and A.ostryaefolia were preyed upon less frequently than clusters on A. hybridus and corn.

Sweet Corn Inhibitor (SCI), a small (11811Da.) protein from the seeds of opaque-2 corn is a potent and specific inhibitor of trypsin and the activated Hageman Factor (Factor βXIIa) of the human blood plasma coagulation system. With the eventual aim of obtaining insight into the structure- function relationships of the selective SCI-pXIIa interaction, a synthetic gene for SCI was cloned into Saccharomyces cerevisiae (yeast) and Escherichia coli (E.coli) expression systems in an attempt to obtain overexpression of the recombinant gene product. The establishment of functional expression, together with an isolation and purification procedure for SCI would provide a system for obtaining selected reactive-site mutants of SCI by cassette- and oligonucleotide-directed mutagenesis. A yeast secretion vector for a truncated form of SCI (tSCI) was constructed by cloning the gene for α-factor prepro-tSCI fusion, downstream to the α-mating factor (MFα1) promoter of yeast. Yeast transformants containing the expression vector failed to express and secrete the desired product. The synthetic gene encoding the complete SCI sequence was cloned into E.coli expression vectors that directed both cytoplasmic and periplasmic expression. In cytoplasmic expression, the SCI gene was cloned directly downstream to the powerful, inducible λ-phage PL- and trc-promoters. No expression was obtained with the latter. With the former, expression levels of up to 3% of the total bacterial protein were obtained. These levels were improved 3- to 4-fold on incorporation of the E.coli dnaY gene product. Solubilisation and refolding of the purified SCI inclusion bodies failed to yield the active, correctly folded product. Failure to obtain an N-terminal sequence indicated an incompletely processed N-terminal methionine. For periplasmic expression, SCI, fused in-frame to the signal sequence of OmpA, a major E.coli outer membrane protein, was cloned into the same λ-phage P_L promoter vector. High levels (=10%) of expression of insoluble SCI were obtained. The nearly homogeneous product was obtained by a two-step procedure, involving ion-exchange chromatography, followed by hydrophobic interaction chromatography. Characterisation by N-terminal sequencing, SDS-PAGE and electrospray mass spectrometry, confirmed the presence of correctly processed SCI in the form of covalently associated dimers. Refolding studies are at present in progress.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 159-167). Also available on the World Wide Web.