Dissertations / Theses on the topic 'Waxy maize'

PURPOSE: The purpose of this study is to examine the effects of different types of carbohydrates on blood glucose response in collegiate soccer athletes at rest. This will help to determine the effectiveness of a carbohydrate supplement in providing sustained energy and maintained performance if ingested prior to a soccer match. METHODS: In a cross-over design, 10 female collegiate soccer players (n= 10, age 20.10 ± .99 years, height 65.55 ± 2.77 inches, weight 64.12 ± 8.36 kilograms) from the University of South Florida reported to the laboratory on five separate occasions after an overnight fast. Once a baseline blood glucose measurement was obtained, subjects ingested one of four different carbohydrate beverages (dextrose, maltodextrin, Vitargo®, and waxy maize) and a control (water). Each subject consumed 1 gram of carbohydrate per kilogram body weight in a 7% solution. Order of carbohydrate and control supplements was randomly assigned for each participant. After the subject ingested one of the test beverages blood glucose measurements were taken at the 30, 45, 60, 90, 120, and 180 minute time points (a total of three hours). The same procedures took place during each subject's visit. A series of one-way analysis of variance (ANOVA) were performed using SPSS 19 to determine differences in the blood glucose response at each time point between the carbohydrate supplements. RESULTS: No significant difference existed between treatments for blood glucose levels at baseline. At 30, 45, and 60 minutes, blood glucose concentrations following dextrose, maltodextrin, and Vitargo® ingestion were significantly higher as compared to the placebo ingestion. No significant difference was observed between waxy maize and placebo at these time points. At ninety minutes the blood glucose concentrations for dextrose and Vitargo® were significantly higher than placebo, and at 120 minutes only Vitargo® was significantly higher than the placebo. Finally, at 180 minutes, the blood glucose concentration for waxy maize was significantly higher than all other treatments. CONCLUSION: The main finding of this study was that waxy maize does not observe a sharp increase in blood glucose response following ingestion but maintains an elevated blood glucose concentration over an extended period of time. All other treatments (maltodextrin, dextrose, and Vitargo®) resulted in a significant rise in blood glucose within the first thirty minutes following ingestion.

Maize is susceptible to biotic and abiotic stresses. The most important abiotic stresses in Africa are drought and low soil fertility. Aflatoxin contamination is a potential problem in areas facing drought and low soil fertility. Three studies were conducted to evaluate maize germplasm for tolerance to stress. In the first study, fifteen maize inbred lines crossed in a diallel were evaluated under drought, low N stress, and well-watered conditions at six locations in three countries to estimate general (GCA) and specific combining ability (SCA), investigate genotype x environment interaction, and estimate genetic diversity and its relationship with grain yield and heterosis. GCA effects were not significant for grain yield across environments. Lines with good GCA effect for grain yield were P501 and CML258 across stresses. Lines CML339, CML341, and SPLC7-F had good GCA effects for anthesis silking interval across stresses. Additive genetic effects were more important for grain yield under drought and well-watered conditions. Heterosis estimates were highest in stress environments. Clustering based on genetic distance calculated using marker data from AFLP, RFLP, and SSRs grouped lines according to origin. Genetic distance was positively correlated with grain yield and specific combining ability. In the second study, synthetic hybrids were evaluated at seven locations in three countries to estimate GCA and SCA effects under low N stress and optimal conditions and investigate genotype x environment interaction. GCA effects were significant for all traits across low N stress and optimal conditions. The highest yielding synthetic hybrids involved synthetics developed from stress tolerant lines. Synthetics 99SADVIA-# and SYNA00F2 had good GCA for grain yield across low N stress conditions. Heterosis was highly correlated with grain yield. Optimal environments explained more variation than stress environments. The third study evaluated the agronomic performance and aflatoxin accumulation of single and three-way cross white maize hybrids at five locations in Texas. Inbreds CML343, Tx601W, and Tx110 showed positive GCA effects for grain yield. Significant GCA effects for reduced aflatoxin concentration were observed in lines CML269, CML270, and CML78 across locations. Differences in performance between single and three-way crosses hybrids were dependent mostly on the inbred lines.

Contemporary learning theories derive much of their explanatory power from the assumption that all stimuli presented vie for associative strength, the assumption of Shared Weight Space (SWS). Theories based on this assumption have proven successful in explaining many of the observed conditioning phenomena in animals. However, work with humans has proven more complex due to outside knowledge, biases, and heuristics (see, e.g., Chapman, 1991; Msetfi et al., 2005; Perales et al., 2004; Tversky & Kahneman, 1974; Viken et al., 2005; Waldmann, 2000 & 2001). The present series of experiments sought to test the assumption of SWS in a task that is less susceptible to the influence of "top-down" factors. An information processing task (i.e., the correlated flankers task) was used so that human participants were completing a central task (i.e., responding to the target) and were unaware as to the importance of the contingencies in the designs, yet were still exposed to them via the irrelevant information (i.e., flankers). Four compound conditioning phenomena were studied in order to test the assumption of SWS. Evidence for the simple predictions coming from SWS theories was mixed. However, a slightly more complex version of these theories can explain the entire pattern of data quite elegantly.

Master of Science<br>Department of Grain Science and Industry<br>Yong Cheng Shi<br>Waxy wheat starch (WWS) containing little or no amylose has unique properties for food and industrial uses. Hydroxypropylation, a widely used means for modifying starches, could enhance functionalities of starch by substituting hydroxyl groups in starch. There are limited numbers of literatures regarding hydroxypropylation of WWS. WWS hydroxypropylated with 3.0-9.0% propylene oxide (PO) were prepared and compared to hydroxypropylated normal wheat starch (NWS) and hydroxypropylated waxy maize starch (WMS). The molar substitution (MS) of the resulting hydroxypropylated NWS, WWS and WMS was 0.055-0.151, 0.048-0.133, and 0.049-0.139, respectively. Gelatinization temperatures and enthalpy of hydroxypropylated starches were significantly lower than those of their unmodified counterparts and the extent of decrease was positively correlated to the MS. Differential scanning colorimetry (DSC) results showed that hydroxypropylation reduced the retrogradation of the starches during the storage after gelatinization but there were differences between the starches. For the same level of PO reaction (3 and 5% PO), hydroxypropylated WWS retrogradated less than hydroxypropylated WMS, suggesting that for the same level of cold storage stability, less PO is needed for WWS. After reacted with 6% PO, MS was 0.092 and 0.094, respectively, for WWS and WMS, and no retrogradation was observed for those hydroxypropylated starches, indicating that at MS ~0.094, hydroxypropyl groups prevents amylopectin chains from re-associating and forming crystalline structures. In contrast, a higher level of PO (9%) was needed to react with NWS to achieve the hydroxypropylated starch with an MS of 0.151 that gave no retrogradation. Consistent with microscopic observation results, Micro-Visco-Amylograph (MVA) analysis showed hydroxypropylated starches developed viscosity at lower temperatures and had improved hot and cold viscosities. The specific characteristics of hydroxypropylated starches are related to the degree of hydroxypropylation. Therefore, it is critical to determine the level of hydroxypropylation in modified starches. 1H NMR is a simple and rapid means of determining hydroxypropyl (HP) group in modified starches. In this study, a method to prepare a HP starch for NMR analysis was improved. The optimum parameters proposed to hydrolyze HP starches were 10% starch solid content, 3.5% (wt.%) DCl in D2O as the solvent, sodium acetate as an internal standard, heating at 90oC for 1 h. Optionally, 6% (v/v) trifluoroacetic acid-d as the water-peak shifting reagent. Six hydroxypropylated starch samples and two commercial cross-linked and hydroxypropylated starch samples were hydrolyzed with this modified method before 1H NMR analysis, and the results of HP group content in the samples were in agreement with the results from an enzyme-catalyzed method, which indicate that the improved acid hydrolysis method is applicable for both hydroxypropylated starch and cross-linked and hydroxypropylated starch.

碩士<br>國立臺灣大學<br>農藝學研究所<br>98<br>In order to understand the association between DNA sequence variation of waxy genes, and kernel appearance traits related to starch composition of maize hybrids grown in Taiwan, two white corns, four waxy corns, four sweet corns, four feed corns and 10 waxy inbreds with various whiteness were used as materials. In this study, extension of electrophoresis time, designation of SNP-specific primer, and TA-cloning of PCR product were used to identify the alleles of hybrid F1. The result indicates that the TA-cloning is the most efficient way to identify hybrid alleles. To determine the kernel appearance traits, total starch content, amylose content, whiteness and L, a, b value were investigated. It was found that sweet corns had the least starch content and waxy corns had the least amylase content, but the most starch and amylose content were produced in the kernel of white corns and feed corns. Results from whiteness and color scale determination showed that high amylose lines had lower whiteness, and the L, a, b values were highly correlated with the pericarp. After comparing and analyzing the DNA sequences and kernel phenotypes, 18 variation sites in exon region, and 64 variation sites in intron region were observed. The sequence variation proportion is approximately 3.5 times higher in intron than in exon, and the down-stream region of exon 12 has the highest rate of variation. Four functional sequence variations, including 30 bp deletion in exon 7, SNPs on 4380 bp(G/A), 4387 bp(G/C) and 4472 bp(G/A), which caused amino acid substitution or deletion in waxy protein, were identified. The waxy gene sequences from 6 monocot species (including maize, barley, rice, millet and sorghum), and 6 dicot species (including potato, cassava, sweet potato and pea) extracted from NCBI database were aligned and analyzed. Only three conserved segments in waxy DNA sequences were identified because of the highly difference among the surveyed sequences. However, conserved regions in monocot crops are larger than in dicot ones. These results revealed the slower evolution rate in waxy genes of monocot species. The result in this study involved in the relationship between DNA sequence variation of waxy allele and kernel starch composition have application potential for breeding corns with different utilizations.

We wanted to develop rapid and cost-effective drought tolerance screening methods for mass amounts of germplasm. In 2009 and 2010, we evaluated sixty-two maize inbred lines and their hybrid testcross progeny using seedling stress response and epicuticular wax accumulation as predictors of drought tolerance. The seedling screening method measured germination, survival and recovery percentages after a series of drought cycles in a greenhouse environment. Eight inbred lines had significantly (P < 0.05) lower germination than the mean estimate, but hybrid testcrosses were not significantly different. The second-to-last day of survival cycle and the second day of recovery cycle best explained genotypic differences for inbred lines and hybrid testcrosses respectively. One inbred line performed well as both an inbred line and hybrid testcross, but poor correlation over the sample set (R2 = 0.0097) was observed. Flag leaves taken at flowering from plants under full and limited irrigation regimes were sampled for epicuticular wax. Extracted wax weight for genotypes was compared as a percentage of leaf weight (percent wxlfwt) and leaf area (percent wxwta). Eleven genotypes had above average percent wxlfwt as both inbred lines and hybrid testcrosses. Thirteen genotypes had above average percent wxwta as either inbred lines or hybrid testcrosses. Irrigation treatment was not significant (P > 0.05). Heritability of percent wxlfwt was 0.17 (inbred lines) and 0.58 (hybrid testcrosses). Heritability of percent wxwta was 0.41 (inbred lines) and 0.59 (hybrid testcrosses). Correlations (R2) for percent wxlfwt and percent wxwta were 0.19 and 0.03, respectively. Heritability of grams of grain per ear and total grain yield was highest in hybrid testcrosses, with no correlation between inbreds and hybrids. The developed seedling screening method easily allowed visible drought tolerance observations in inbred lines and hybrid testcrosses but does not seem heritable in our germplasm. Epicuticular wax weight is not an ideal primary trait to evaluate for drought tolerance, but may be a good candidate to observe as a secondary trait in relation to grain yield production in hybrids. Results from this research best supports breeder selection of hybrid germplasm using seedling drought tolerance in conjunction with epicuticular wax.

The maize leaf has three main axes of growth, with an asymmetric distribution of tissue types along each axis. This study focuses on three mutants, Wavy auricle in blade1-R (Wab 1-R), liguleless1-R (lg1-R) and milkweed pod1-R (mwp1-R) that disrupt axial patterning of maize leaves. Dominant Wab1 mutations disrupt both medial-lateral and proximal-distal patterning. Wab1 leaf blades are narrow and ectopic auricle and sheath-like tissues extend into the leaf blade. Previous analyses have shown that Lg1 acts cell-autonomously to specify ligule and auricle tissues. The current study reveals additional roles in defining leaf shape. The recessive lg1-R mutation exacerbates the Wab1-R phenotype; in the double mutants, most of the proximal blade is deleted and sheath tissue extends along the residual blade. A mosaic analysis of Wab1-R was conducted in Lg1 and lg1-R backgrounds to determine if Wab1-R affects leaf development in a cell-autonomous manner. Normal tissue identity was restored in all wab1/- sectors in a lg1-R mutant background, and in three quarters of sectors in a Lg1 background. These results suggest that Lg1 can influence the autonomy of Wab1-R. In both genotypes, leaf-halves with wab1/- sectors were significantly wider than non-sectored leaf-halves, suggesting that Wab1-R acts cell-autonomously to affect lateral growth. mwp1-R is a recessive mutation that specifically affects patterning of sheath tissue. Characterisation of the mwp1-R phenotype revealed that mwp1-R husk leaves and the sheaths of vegetative leaves develop pairs of outgrowths on the abaxial surface associated with regions of adaxialised tissue. In situ hybridisation confirmed that disruptions to adaxial-abaxial patterning are correlated with misexpression of leaf polarity genes. Leaf margins and fused organs such as the prophyll are most severely affected by mwp1-R. The first two husk leaves normally fuse along adjacent margins to form the bi-keeled prophyll. In the most severe cases the mwp1-R prophyll is reduced to an unfused, two-pronged structure and keel outgrowth is significantly reduced. We speculate that the adaxial-abaxial patterning system has been co-opted during evolution to promote outgrowth of the keels in normal prophyll development. The results of this study place Mwp1, wab1 and Lg1 in a network of genes that regulate leaf polarity and axial patterning.

Soil degradation and low crop productivity negatively affect the food security of smallholder farmers in West Africa. Various agricultural techniques have been developed as components of food security interventions, but their effectiveness in addressing food insecurity in part depends upon farmers’ willingness to adopt these techniques. Likewise, adoption depends upon the effectiveness of these techniques in fulfilling farmers’ objectives. The institutional and biophysical environments mediate not only the effectiveness of the techniques, but also how farmers value a technique. This study examined the evidence for fertilizer microdosing as a form of agricultural intensification and the socio-economic conditions that influence its adoption among smallholder farmers. A census was conducted in one village in northwest Benin that had recently seen the introduction of fertilizer microdosing. Key household-level determinants of adoption identified in the literature—household resources, household demographics, and access to inputs— were included in the household surveys. Using partial budgeting analysis and yield data from demonstration plots, the relative profitability of fertilizer microdosing was calculated as a necessary condition of adoption. Drawing from farmers’ stories, the potential value of microdosing was contextualized within the larger social and institutional context. Based upon the village census, there was little adoption outside of the research project that introduced microdosing to the village. Households using microdosing (predominantly found within the research project) had, on average, higher socio-economic status, more cultivable land and larger labour forces. Profitability analysis indicated that microdosing was on average less profitable than the point-source application of the recommended dosage rate in Benin (the common alternative). However, farmers still expressed a desire to microdose, due to poorly functioning input markets, poor infrastructure, and lack of access to financial instruments, all of which limited the availability, access and utilization of inorganic fertilizer.