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Dissertations / Theses on the topic 'Maize plant'

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Published: 4 June 2021
Last updated: 9 February 2022

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1

Small, Ian. "Resistance in maize to Fusarium verticillioides and fumonisin." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4803.

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Thesis (MScAgric (Plant Pathology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Maize is the most important cereal crop produced in southern Africa. Maize producers, processors, and consumers in the region, however, are affected by Fusarium ear rot, a disease caused primarily by the fungal pathogen Fusarium verticillioides that reduces grain quality and potentially contaminates the grain with mycotoxins (fumonisin). Due to the threat of fumonisin to human and animal health, and the economic losses associated with reductions in grain quality, strategies aimed at the prevention of Fusarium ear rot and fumonisin contamination are required. These preventative strategies should be focused on protecting the crop prior to harvest, as damage is known to occur in the field before storage. Chapter 1 provides the reader with a broad overview of maize production in southern Africa, the disease Fusarium ear rot caused by F. verticillioides, and the contamination of grain with fumonisins. Potential disease management practices are summarised, and the role of host resistance and its underlying mechanisms emphasised. Finally, the use of plant breeding and resistance elicitors as methods to enhance host resistance in maize towards Fusarium ear rot and fumonisin contamination are discussed in detail. The planting of maize genotypes with enhanced host resistance potentially offers the most efficient method to reduce Fusarium ear rot and mycotoxin contamination. If plant breeding is to be used to enhance resistance, sources of genetic resistance are required. These sources would ideally be in the form of locally adapted maize genotypes, such as inbred lines. In Chapter 2, maize inbred lines used in local breeding programmes, which are adapted to the production conditions in southern Africa, were evaluated as potential sources of resistance to Fusarium ear rot and fumonisin contamination. If inbred lines with good genetic resistance were to be identified they could be used by breeding programmes to develop commercial maize cultivars with resistance to Fusarium ear rot and fumonisin. Activation of resistance responses in normally susceptible maize genotypes using resistance elicitors could provide a novel management strategy for Fusarium ear rot control, as no commercial cultivars with complete resistance to this disease have been identified in southern Africa. Elicitors have previously been found to induce resistance to plant pathogens, mostly in dicotyledonous crops, but the ability of a range of elicitors to reduce Fusarium ear rot and fumonisin contamination in maize has not been investigated. In Chapter 3, a variety of chemical elicitors that induced resistance in other plant-pathogen systems were selected based on the different defence pathways that they stimulate, and evaluated in field and greenhouse trials. Three commercial maize hybrids were included in the trial, conducted at two different field sites, and the elicitors were tested for their ability to reduce Fusarium ear rot and fumonisin contamination of grain, as well as for their effect on yield. These elicitors could be applied in the field as part of an integrated disease management programme, are environmentally friendly, and would be affordable to commercial producers that produce the majority of maize in South Africa.
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2

Buckler, Carlyn Suzanne Keith. "Miniature plant phenotype and mitochondrial porins in maize /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9946248.

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3

Dilkes, Brian R. "Analysis of maize endosperm endoreduplication." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289871.

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During maize endosperm development, the cell cycle in the majority of cells switches from a mitotic to an endoreduplication cell cycle. This results in cells of varying ploidies within the tissue, and is presumed to be a factor in its rapid growth. Investigating the inheritance of variation in endoreduplication in maize endosperm will begin to elucidate the genetic mechanisms controlling it. It has been hypothesized that retinoblastoma-related proteins (RRBs) negatively regulate the G1/S transition during both mitotic and endoreduplication cell cycles. Testing this hypothesis in both mitotic cells and endoreduplicating endosperm cells will further our understanding of the molecular mechanisms regulating endoreduplication. Flow cytometry was used to assess the variability of endoreduplication in endosperms of maize inbred lines. High levels of endoreduplication were observed in popcorns relative to Midwestern dent corns. To study the genetic regulation of endoreduplication, four inbreds were crossed to B73 and developing endosperms from parental, reciprocal F1, and backcross generations were subjected to flow cytometric analysis. Maternal zygotic effects, often considered a form of parental imprinting, and maternal sporophytic effects were detected. To test the feasibility of introgressing a high endoreduplication phenotype into a Midwestern dent inbred line, a backcross population was generated using B73 as the reciprocal parent and the popcorn Sg18. The heritabilities calculated from an analysis of the backcross population generally agree with the values calculated in the larger crossing experiments. The Wheat Dwarf Virus RepA protein binds RRBs and is predicted to activate the cell cycle. RepA and the maize RRB, ZmRb1, were tested for cell cycle regulatory activity in tobacco BY-2 cells and determined to be an activator and repressor, respectively. The effect of RepA on endoreduplication was evaluated in both mitotically-active maize callus cultures and developing endosperms. Flow cytometric measurements of nuclear ploidy showed that RepA expression was sufficient to convert a mitotic into an endoreduplication cell cycle in calli but had no discernable effect on endopolyploidy in developing endosperm by 18-days after pollination (DAP).
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4

Blanding, Carletha R. "Maize gene expression UV response patterns reveal coordinate regulation of many genes /." Electronic version (Microsoft Word), 2005. http://dl.uncw.edu/etd/2005/blandingc/carlethablanding.doc.

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5

Clayton, Helen. "Carbohydrate oxidation in maize bundle sheath." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335719.

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6

Wu, Yajun. "Cell wall proteins and growth maintenance of the maize primary root at low water potentials /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720531.

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7

Zambrano, Mendoza Jose Luis. "Genetic Architecture of Resistance to Phylogenetically Diverse Viruses in Maize." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373285155.

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8

Smith, Jane Louise. "The characterisation of higher plant phytoene desaturase." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313999.

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9

Turnbull, Christopher James. "Studies of oxalate, germin and plant development." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369570.

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10

El-Maleh, Abdulkader A. "Transgenic tobacco containing the maize T-urf13 gene as a novel host for the maize pathogen Cochliobolus heterostrophus race T." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360269.

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11

Nderito, Waturu Charles. "Entomopathogenic nematodes (Steinernematidae and heterorhabditidae) from Kenya." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265109.

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12

Purdue, Paul Edward. "Nuclear genes and protein import into maize mitochondria." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/12812.

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13

Rogers, Jennifer Jacqueline Mavis. "Mutational analysis of the maize auxin binding protein, ABP1." Thesis, University of the West of England, Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249341.

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14

Hodges, D. Mark. "Chilling effects on antioxidant systems of maize (Zea mays L.)." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9830.

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When chilled, plants produce greater amounts of toxic oxygen compounds than they do under non-stressed conditions. These toxic oxygen compounds have the potential to cause severe damage to plants. Plants have evolved antioxidant systems which can scavenge these toxic oxygen compounds and thus allow for the avoidance of their detrimental effects. The purpose of this thesis was to characterize antioxidant capacities of differentially chilling sensitive lines of maize (Zea mays L.) in order to test the hypothesis that the most chilling sensitive lines would have less antioxidant capacity and, hence, less ability to scavenge damaging toxic oxygen compounds, than the more tolerant lines. Three objectives were set to test this hypothesis. The first objective was to select out relatively chilling sensitive and tolerant inbred maize based on their physiological responses to chilling. This first objective was successfully met by subjecting the inbred lines to laboratory chilling tests at the germination stage and early growth stages. Field trials which assessed physiological parameters at both the emergence and early growth phases were then carried out which confirmed laboratory results. The second objective of this thesis was to test if the selected chilling sensitive inbred maize lines had less antioxidant capacities than the tolerant. To this end, activities of the antioxidant enzymes catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (ASPX; EC 1.11.1.11), superoxide dismutase (SOD; EC 1.15.1.1), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and glutathione reductase (GR; EC 1.6.4.2), along with concentrations of the antioxidant compounds ascorbate, glutathione, $\beta$-carotene, and $\alpha$-tocopherol and levels of the general metabolic indicators of chilling stress (carbohydrates, chlorophyll, and soluble proteins) were assessed. These parameters were assessed at three developmental stages (first, third and fifth leaf stages) and under control (25$\sp\circ$C) and both short- and long-term chilling ($11\sp\circ$C) regimes. This second objective was successfully met. Significantly lower percent of control activities of the antioxidant enzymes ASPX, MDKAR, and CAT, were observed in the most chilling sensitive inbred line as compared to the tolerant at the first leaf stage of development. The third objective of this thesis was designed to determine if there were similar results for antioxidant capacities and metabolic indicator concentrations for the chilled hybrids as there were for the inbred maize lines. Thus, a complete diallel cross between the above selected inbreds was made, and the resulting hybrids then classified as relatively chilling sensitive or tolerant depending upon how they performed in the laboratory germination and early growth stage screening tests with confirmation in the field. The hybrids were grown until the third leaf stage under short-term chilling (11$\sp\circ$C) and assessed for activities of the antioxidant enzymes and concentrations of antioxidant compounds and metabolic stress indicators. This third objective was successfully met. The chilling sensitive maize hybrids were found to have lower, although not significantly so, percent of control activities of CAT, MDHAR, and ASPX than the chilling tolerant hybrids, paralleling the results of the parental inbreds. (Abstract shortened by UMI.)
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15

Wasikowski, Rachael A. "The Maize TFome 2.0: Genomic Analysis of Transcription Factor Repertoire." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo152545363525107.

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16

Chauhan, Ramola. "A study of filamentous viruses in maize and smallgrains." Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22013.

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Bibliography: pages 175-184.
The occurrence of maize dwarf mosaic virus (MDMV) in field grown maize was investigated. For this purpose, maize showing mosiac symptoms was collected from different maize growing areas in South Africa by Prof. M.B. von Wechmar. These samples from Transvaal, Orange Free State and Natal were then investigated for the presence of MDMV and possible strains of this virus. Three virus isolates were purified and partially characterised. These isolates were serologically compared together with a fourth isolate SCMV 4975, obtained from the U.S., to establish strain relationships.
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17

Pennington, Paul Douglas. "An analysis of interploidy crosses in maize." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:61594fab-c6a0-4d18-81d8-3578a7e678d4.

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Reciprocal crosses between plants containing different genome numbers have been demonstrated to show alternate phenotypes in many species and are often lethal. The effects of interploidy crosses on kernel development in maize (Zea mays) have been reassessed using markers for two cell domains: the aleurone and the basal endosperm transfer layer (BETL); and by monitoring gene expression. The study confirms previous observations and offers novel insights into genomic interactions. Endosperms from maternal excess crosses (tetraploid mother, diploid father) displayed reduced mitotic activity, and an accelerated rate of differentiation generally, including early starch accumulation, and earlier, atypical aleurone formation. The BETL failed to form normally, being replaced with aleuronelike cells, except for a few interspersed cells. Gene expression was altered, including those encoding cell domain markers and storage molecules. Paternal excess endosperms (diploid mother, tetraploid father), showed an increase in cellular proliferation. Generally, differentiation was delayed: starch accumulation began late, and formation of the aleurone layer was delayed, and was morphologically highly irregular. BETL specification was also disturbed, with only a few cells showing characteristic wall modifications very late in development. Later development of the whole endosperm was characterized by ectopic gene expression, and zones of high cell proliferation. A greater proportion of the genome was mis-expressed in these crosses, reflecting the more extreme phenotype. Although expression levels of marker genes did not reflect the failure to develop a normal BETL, it may be that the cells in the BETL region had undergone an modified developmental program. This work is considered in the context of evolutionary models which state that different parental roles lead to differential expression of genes from their respective genomes, and is compared with evidence from arabidopsis. The current study is considered generally supportive of such models.
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18

Dante, Ricardo Augusto. "Characterization of cyclin-dependent kinases and their expression in developing maize endosperm." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1040%5F1%5Fm.pdf&type=application/pdf.

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19

Vigier, Bernard. "Host plant resistance and epidemiology of Fusarium ear rot in maize." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ28380.pdf.

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20

Mao, Jingqin. "Improved resistance to insects in maize (Zea mays L) and cowpea (Vigna unguiculata L)." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27152.

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A novel alteration in secondary metabolism of maize transformed with wheat oxalate oxidase gene (OXO) was determined using HPLC and microscopy. Phenolic concentration was significantly increased, but DIMBOA synthesis was down-regulated. The high levels of soluble phenolic acids, in particular free ferulic acid, most likely contributed to the insect resistance in the OXO maize. To facilitate future cowpea transformation with the OXO, a stable in vitro regeneration system was established in blackeye cowpea via shoot organogenesis. The optimal initiation medium comprised MS salts, B 5 vitamins, 2 mg 1-1 BAP, 3% sucrose and 0.8% agar at pH 5.8. The highest initiation frequency and shoot number were obtained from the shoot apices of 3-5 days old seedlings. For shoot elongation, 0.5-5.0 mg 1-1 GA3 was required. Rooting medium was MS salts supplemented with B5 vitamins, 3% sucrose and 0.8% agar.
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21

Lopez-Valenzuela, Jose A. "Characterization of proteins influencing the nutritional qualityof maize (Zea mays L.) endosperm." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280366.

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Elongation factor 1A is one of the lysine-rich proteins increased in o2 mutants, and its concentration is highly predictive of the protein-bound lysine content of the endosperm. Understanding the biological basis of this relationship could help to explain the mechanisms of lysine accumulation in the endosperm, providing new insights for developing maize genotypes with better nutritional quality. Three different eEF1A isoforms were purified from developing endosperm and investigated in their accumulation, structural and functional activities. The accumulation of the isoforms appears to be developmentally regulated and independent of the o2 mutation. The purified proteins differed in their ability to bind F-actin in vitro, suggesting they are functionally distinct. The isoform that binds actin most effectively was the most predominant in high eEF1A genotypes, which may be related to enhanced cytoskeleton formation, and therefore increased synthesis of cytoskeleton-associated proteins in these genotypes. Tandem mass spectrometry revealed each isoform is composed of the four same gene products, which are modified post-translationally by methylation and phosphorylation. The chemical differences that account for their different actin binding activities could not be determined. Recombinant inbred lines varying in eEF1A content were developed from a cross between a high (Oh51Ao2) and a low (Oh545 o2) eEF1A inbred. The parental inbreds and RILs with the highest and lowest eEF1A content were used to investigate patterns of gene expression and protein synthesis. Transcript profiling with an endosperm EST microarray identified about 110 genes coordinately regulated with eEF1A. These genes encode proteins involved in several biological structures and processes, including the cytoskeleton, the endoplasmic reticulum and the protein synthesis apparatus. The content of alpha-zein and several cytoskeletal proteins was measured in high and low eEF1A inbred lines, and the levels of these proteins were found to correlate with that of eEF1A. Thus, higher levels of eEF1A may be related with a more extensive cytoskeletal network surrounding the rough ER and increased translation of mRNAs encoding cytoskeleton-associated proteins, all of which contribute significantly to the lysine content of the endosperm.
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22

Mayfield, Kerry L. "Preharvest aflatoxin in maize genotypes under inoculation with Aspergillus flavus." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1184.

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23

Thornsberry, Jeffry M. "Mitochondrial-chloroplast interactions : studies using the NCS mutants of maize /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9946304.

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24

Burt, Andrew J. "Phytochemical mediation of post-harvest insect resistance in tropical maize." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/22632.

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25

Lucy, Andrew P. "Pathways to systemic invasion of plants by maize streak and other viruses." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338088.

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26

Formanová, Nataša. "A complex synthesizing the maize mitochondrial plasmid RNA b /." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68173.

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RNA b is the most abundant member of a family of autonomously replicating single- and double-stranded RNA plasmids found in mitochondria of several maize races. The extent to which this molecule associates in vivo with proteins was investigated by both rate zonal and CsCl equilibrium density gradient centrifugations of clarified lysate of mitochondria from maize plants with the S-type cytoplasm. A soluble endogenous complex of RNA b, responsible for synthesis of the more abundant (+) RNA b strand in in vitro conditions (in mitochondrial lysate), was identified. The complex had a density of 1.49 g/cm$ sp3$ but a surprisingly low sedimentation coefficient, only slightly larger than the naked RNA b. Only a minor fraction of RNA b molecules were bound in the complex; the majority of RNA b sedimented as naked RNA molecules. Complexes synthesizing other, less abundant, maize RNA plasmids were not identified. However, in vitro synthesis of all RNA plasmid species in mitochondrial lysate was resistant to heparin, suggesting that in all cases preformed RdRp-RNA template complexes, capable of elongating in vivo preinitiated RNA plasmid strands, were present.
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27

Miller, Erin Suzanne. "Increasing Expression of Hepatitis B Surface Antigen in Maize through Breeding." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1359.

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The hepatitis B virus (HBV) is a common virus, with two billion people infected worldwide. It causes approximately 600,000 deaths each year, despite the availability of an effective vaccine since 1982. Maize as a platform for oral vaccination can supply a heat stable vaccine, which does not require syringes or trained personnel to administer. The Hepatitis B Surface antigen was transformed into maize and this seed was used to evaluate expression levels through the breeding process. The transgene was transferred into two elite maize inbreds by backcrossing. Highest expressing ears were selected each generation until approximately 99% commercial parent was obtained with a single gene coding for the vaccine present. Selected individuals were crossed to create hybrid plants. This work was done to create high expressing high yielding lines that could be used as a plant-based oral vaccine for Hepatitis B.
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28

Medina, Rachel Morales. "Investigation of Maize Root Exudates on Heterodera glycines Populations under Direct and Indirect Exposure." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482499805741097.

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29

Moyo, Robin Mkhokheli. "Nutritional quality of maize ensiled with wet distillers grains for sheep." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/25900.

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Four trials were conducted to evaluate the effects of ensiling whole plant maize with wet distillers grains with solubles (WDGS) on its preservation and nutritive value. In the first study, WDGS was blended with whole maize plants at 0% (control), 10%, 20%, 30% and 40%, and ensiled for 120 days in bottle silos in a complete randomized design. Fermentation was monitored by taking samples at day 0, 7, 21, 42 and 120. Results showed a steady decrease (P<0.05) in dry matter (DM) concentration with increasing level of WDGS inclusion. Final silage pH was lowest (P<0.05) for the 40% WDGS treatment (pH 3.62) and highest for the 10% WDGS treatment (pH 3.79). There was no effect (P>0.05) of level of WDGS inclusion on initial buffering capacity (day 0), as well as for day 42 and 120 samples. Lactic acid was higher (P<0.05) at day 120 for the control treatment than those blended with WDGS, which did not differ significantly. The concentration of acetic acid was higher value (P<0.05) for silage treatments blended with WDGS than the control, with that of 40% WDGS level of inclusion recording the highest (P<0.05). The control and 40% WDGS treatments had lower (P<0.05) ammonia nitrogen concentration (g/kg N) than the other treatments at day 120. The second trial involved monitoring ruminal fermentation characteristics of cannulated sheep fed three experimental diets. Formulated diets contained maize silage mixed with 24% dried distillers grains with solubles (MS DDGS treatment ), maize silage mixed with 19.5% sunflower oilcake meal (MS SOM treatment), and silage blend of 91% of whole maize plant/9% WDGS (WDGSMS treatment), all on a DM basis, to obtain iso-nutrient diets. The mean value for rumen pH, NH3N and total VFA concentrations among diets did not differ (P>0.05) among treatments. The individual VFA were similar with only butyric acid being lower (P<0.05) in sheep fed WDGSMS. There were no differences in the acetic:propionic acid ratio among treatments. The third trial involved the determination of DM degradability of the three formulated experimental diets using the nylon bag technique. Effective degradability was measured at two outflow rates, 2% and 5%. The diets did not differ (P>0.05) for washing losses (avalue), slowly degradable DM fraction (b-value) and rate of degradation of DM (c-value). Treatment MS SOM recorded the highest effective degradability with MS DDGS having the lowest at 2% outflow rate. The effective degradability value at 5% outflow rate for WDGSMS was not significantly different from that of MS SOM and MS DDGS, which differed significantly. In the final study, experimental diets were fed to three groups of eight lambs in a growth performance trial. The groups offered MS DDGS and MS SOM had superior (P<0.05) final mass (g/head), average daily intake (gDM/kg0.75) and average daily gain (g/head/day), than those offered WDGSMS. The feed conversion ratio did not differ (P>0.05) among all treatments.
Dissertation (MSc(Agric))--University of Pretoria, 2011.
Animal and Wildlife Sciences
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30

Azevedo, Demostenes Marocos Pedrosa de. "The influence of plant population on weed supression in maize/bean intercropping." Thesis, University of East Anglia, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237002.

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31

McGinley, Susan. "Cracking the Code in Maize: Gene Studies Offer Tools for Plant Improvement." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/622229.

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32

Shu, Xiaomei. "Pathogenesis and Host Response During Infection of Maize Kernels by Aspergillus flavus and Fusarium verticillioides." Thesis, North Carolina State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3647580.

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Developing maize kernels are vulnerable to colonization by microbes. When colonization allows proliferation of the microbe at the expense of the host, disease occurs. The ascomycete fungal pathogens Aspergillus flavus and Fusarium verticillioides are capable of colonizing maize kernels, causing ear rots and contamination of the kernel with mycotoxins. These diseases lead to significant losses of crop yield and quality, and constitute a threat to food safety and human health. Thus, the significance of these diseases has prompted extensive research efforts to understand these plant-parasite interactions. However, pathogenesis and resistance mechanisms remain poorly characterized, hampering the development of effective control strategies. No commercial maize lines are completely resistant to these fungi. We applied an integrated approach consisting of histology, in situ gene expression and transcriptional profiling to better understand the nature of the interactions that occur between maize kernels and these fungi. Maize inbred line B73 was hand pollinated and inoculated with either A. flavus or F. verticillioides by wounding the kernel with a needle bearing conidia. Histological staining of the kernel sections revealed fungal mycelium in kernels adjacent to the inoculation site by 48 hours post inoculation (hpi), and in all tissues at 96 hpi. Compared with F. verticillioides, A. flavus more aggressively colonized kernel tissue and formed a unique biofilm-like structure around the scutellum. Transcriptome profiling using RNA-sequencing (RNA-seq) coupled with pathway analysis showed that these fungi were recognized by the kernel tissues prior to visible colonization. Infection of the kernel by these fungi induced transcriptional changes in defense-related genes, hormone signaling networks, as well as primary and secondary metabolism pathways. To dissect tissue-specific responses of the kernel, RNA in situ hybridization and histological staining were carried out in adjacent serial sections. We found that two maize genes, pathogenesis related protein, maize seeds (PRms) and shrunken-1 (Sh1) , were expressed in the aleurone and scutellum during infection by these fungi. By staining the adjacent sections, we found that these genes were induced in the tissue before the establishment of fungal colonization. Integration of histology, in situ gene expression and transcriptional profiling to study pathogenesis of maize kernels by these two fungi revealed distinctive and common features between the two pathosystems, and provided information that will facilitate the development of resistance genotypes in maize.

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33

Hable, Whitney Elizabeth 1967. "Expression and regulation of phytoene desaturase during maize seed development." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282172.

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An essential component of development is the accumulation of specific metabolites in a temporal and tissue-specific manner. The growth regulator abscisic acid (ABA), which accumulates at a specific time during seed development, is required for seed maturation and prevents the premature developmental switch from dormancy to germination ABA accumulates differently in two tissues of the seed; levels in the embryo are several-fold higher than in the endosperm and the temporal accumulation of ABA is also different between these tissues. To begin to understand how ABA accumulation is regulated during seed development, the regulation of ABA biosynthesis was investigated. The approach taken was to examine the expression of the biosynthetic enzyme, phytoene desaturase (PDS), which catalyzes a regulated step in ABA synthesis in several other organisms (Bramley, 1985, Sandmann et al., 1989, Hugueney et al., 1992 and Giuliano et al., 1993). Unlike ABA accumulation, PDS transcript and protein levels were higher in the endosperm than in the embryo. The spatial difference in PDS levels did correlate with levels of the pathway intermediate, beta-carotene, suggesting that PDS may control the synthesis of ABA precursors while subsequent enzymes may regulate ABA accumulation. The temporal expression of Pds was also unrelated to ABA accumulation. In the endosperm, transcript levels were initially high and declined during desiccation while protein levels remained high throughout development. In the embryo, transcript levels were low and constant while protein levels declined. There are several maize mutants (viviparous mutants) disrupted in ABA biosynthesis, resulting in decreased levels of ABA and premature germination. Analysis of the Pds allele and transcript in the viviparous-5 mutant showed that the gene contains multiple insertions and deletions, giving rise to a larger transcript. In addition, the 55 kDa PDS protein was not detected in the vp5 mutant by immunoblot analysis, indicating that the vp5 phenotype results from a mutation at the PDS locus. To determine whether the wild type protein encoded by the ABA mutant, vp2, or the pathway intermediate, lycopene, regulate PDS, transcript and protein levels were compared in wild type and mutant (vp2 and vp7, respectively) seeds. The levels of PDS were not significantly different in vp2 or vp7 wild type and mutant seeds, suggesting that neither the VP2 protein nor lycopene regulate PDS at the steady-state transcript or protein level.
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34

Ge, Xin. "Characterization of the Genome of Maize Chlorotic Dwarf Virus and an Associated Satellite RNA." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391600232.

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35

Khanna, Anupama Q. Weber David F. "Effect of B chromosomes on recombination frequency in maize." Normal, Ill. Illinois State University, 1998. http://wwwlib.umi.com/cr/ilstu/fullcit?p9835912.

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Thesis (Ph. D.)--Illinois State University, 1998.
Title from title page screen, viewed July 5, 2006. Dissertation Committee: David F. Weber (chair), Marjorie A. Jones, Anthony Otsuka, Derek McCracken, Radheshyam Jayaswal. Includes bibliographical references (leaves 85-91) and abstract. Also available in print.
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36

Chege, Ayub Getheyo. "Management of plant nutrients in smallholder farming systems of Western Kenya." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341197.

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37

Sowa, Aleksander. "Physiological studies on a nonsymbiotic plant haemoglobin in a transgenic maize cell system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32462.pdf.

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38

Monakisi, Charlotte. "N₂ fixation, plant mineral nutrition and C metabolites in cowpea/maize cropping systems." Bachelor's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/25932.

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The objective of this study was (1) quantify N₂ fixation in sole and mixed cropped cowpea, (2) To access nutrient assimilation by component species in the cropping system, and (3) to determine the effects of cropping system on C metabolites. At harvest the dry mass of both cowpea and maize were highest in sole crops. There was a significant difference in % nitrogen of maize and cowpea plants from the different cropping systems. Total nitrogen content was highest in sole cropped maize and cowpea plants with sole cowpea fixing the most N₂. δ¹⁵N values were lower for the shoots of symbiotic cowpea compared to the maize. Root δ¹⁵N values were also generally lower in cowpea than in maize. The %N derived from fixation (Ndfa) was similar for sole, intra and intercropped cowpea. However the amount of N fixed was significantly greater in sole cowpea compared to intra- and intercropped cowpea. When nutrient uptake and assimilation was assessed in the cropping system, it was found that mineral elements such as Ca, Mg, Cu, Zn and B occurred in significantly greater concentrations in the N₂-fixing legume compared to the cereal partner. However the concentration of soluble sugars and starch remained the same for both shoot and roots of cowpea and maize plants in the cropping system.
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39

Braun, David Meyer. "Maize receptor-like protein kinase signal transduction and function /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841268.

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40

Bush, Brian Joseph. "Fusarium verticillioides Infection, Fumonisin Contamination and Resistance Evaluation in North Carolina Maize." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010718-161312.

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Fusarium ear rot and fumonisin contamination are serious problems for North Carolina maize growers. With the discovery of fumonisin toxicity to animals and humans, and the finding that no maize genotypes are resistant to Fusarium verticillioides infection or fumonisin contamination, management strategies for limiting fungal and toxin contamination of harvested grain are necessary. Maize ears were harvested weekly for 14 or 15 weeks after pollination and assayed for percent kernel infection and fumonisin contamination. Kernel infection and fumonisin contamination occurred before kernel maturity and increased throughout the season, with kernel infection peaking 7 to 10 weeks after pollination. Data from this experiment and data from grower?s fields indicate that early harvest is necessary to limit rotten kernels and fumonisin in harvested grain.Difficulty in identifying resistant genotypes has limited the development of more resistant hybrids. Many inoculation techniques have been employed to reproduce Fusarium ear rot with marginal results, primarily because differentially resistant and susceptible hybrids were not used to identify promising inoculation techniques. In my study, ears were treated with different inoculation techniques to reproduce ear rot and fumonisin contamination in hybrids of known resistance to Fusarium ear rot. Two inoculation techniques, Pinbar and Silk Channel, were able to separate hybrids on visible ear rot and fumonisin contamination. Addition of inoculum to ears appears important for screening hybrids for resistance to Fusarium ear rot and fumonisin contamination.

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41

Mejia, Guerra Maria Katherine. "Characterization of the Building Blocks of the Maize Gene Regulatory Grid." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448452906.

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42

Lopez-Montes, Antonio José. "Integrating farmers' knowledge and decision-making in the planning of participatory research of cassava/maize intercropping." Thesis, Bangor University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248899.

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43

Morse, Stephen. "The role of hydroxamic acids in conferring resistance to aphid pests of seedling maize (Zea mays)." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293605.

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44

Greenlee, Diana Mae. "Accounting for subsistence variation among maize farmers in Ohio valley prehistory /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6565.

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45

Probst, Claudia. "Fungi Associated with Aflatoxin Contamination in Africa." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/201499.

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Aflatoxins are secondary metabolites produced by members of the fungal genus Aspergillus. Immunosuppressive and carcinogenic activities of these toxins negatively impact human health especially in developing countries. Severity of contamination is influenced by both fungal community structure and the environment to which the crop is exposed either prior to or after harvest. In 2004, a severe episode of lethal human aflatoxicosis occurred in the Eastern Province of Kenya. Analysis of fungal community structure revealed that this event was caused by a previously unknown fungal lineage closely resembling the S strain morphotype of Aspergillus flavus. Fungal communities associated with maize produced in affected regions of Kenya were invariably dominated by the new fungal lineage and its incidence was strongly correlated with maize aflatoxin content. Analyses of fungal communities of maize grown in adjacent Kenyan provinces showed that incidences of the new lineage are limited outside the Eastern Province where the aflatoxicoses outbreaks occurred. Multi-locus phylogenetic analyses suggest the newly identified Kenyan lineage is closely related to the B and G aflatoxin producing species A. minisclerotigenes, and more distantly related to both the A. flavus S strain and an unnamed taxon with similar morphology endemic in West Africa (strain SBG). Sequence analyses of the cypA aflatoxin biosynthesis gene identified a previously unknown 2.2 kb deletion unique to the Kenyan lineage and coherent with its phylogenetic placement. A polyphasic approach was used to study aflatoxin-producing fungal communities, with emphasis on occurrence of fungi with S strain morphology, in Sub-Saharan Africa. Four phylogenetically distinct groups of fungi with S strain morphology were identified with restrictions to West Africa (strain SBG) or Central and East Africa (A. flavus S strain, A. minisclerotigenes, the new lineage). Aflatoxin production in synthetic media was a poor predictor of aflatoxin production in viable maize grain. An in vitro assay was developed to predict the aflatoxin-producing potential of fungal isolates in maize. This screen was used to identify atoxigenic isolates of A. flavus with potential value for biological control within highly toxic Aspergillus communities associated with maize production in Kenya. These atoxigenic isolates have potential value for mitigating aflatoxin contamination in Kenya.
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46

Raymond, Fred Douglas. "Reducing Corn Yield Variability and Enhancing Yield Increases Through the Use of Corn-Specific Growth Models." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36304.

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Crop simulation models (CSMs) are used to evaluate management and environmental scenarios on crop growth and yields. Two corn (Zea Mays L.) crop growth simulation models, Hybrid-Maize, and CERES-Maize were calibrated and validated under Virginia conditions with the goal of better understanding corn response to variable environmental conditions and decreasing temporal yield variation. Calibration data were generated from small plot studies conducted at five site-years. Main plots were plant density (4.9, 6.2, 7.4, and 8.6 plants m-2); subplots were hybrids of differing relative maturity (RM) [early = Pioneer® Brand â 34B97â (108 day RM); medium = Pioneer® Brand â 33M54â (114 day RM); and late = Pioneer® Brand â 31G66â (118 day RM)]. Model validation was generated from large scale, replicated strip plot trials conducted at various locations across Virginia in 2005 and 2006. Prior to model adjustments based on calibration data, both CSMs under predicted corn grain yield in calibration and validation studies. CERES-Maize grain yield prediction error was consistent across the range of tested plant density while accuracy of Hybrid-Maize varied with plant density. Hybrid-Maize-estimated biomass production was highly accurate. Greater leaf area index (LAI) and biomass production were measured than was predicted by the CERES-Maize CSM. Both CSMs were modified based on calibration data sets and validated. Validation results of the calibrated CSMs showed improved accuracy in simulating planting date and environmental effects on a range of corn hybrids grown throughout Virginia over two years. We expect that both modified models can be used for strategic research and management decisions in mid-Atlantic corn production.
Master of Science
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47

Zanin, Claitson Gustavo. "Área foliar, senescência e uniformidade de desenvolvimento na adaptação ao adensamento de plantas de cultivares de milho com bases genéticas contrastantes." Universidade do Estado de Santa Catarina, 2007. http://tede.udesc.br/handle/handle/1240.

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The increment in plant density is an alternative to maximize solar radiation interception and to increase maize grain yield. However, it can also reduce the crop photosynthetic activity and limit its efficiency to convert carbohydrates to grain production. Increases in maize hybrid s tolerance to crowding have been reported in different production areas around the world. Two traits that may contribute to this feature are the slower leaf senescence during grain filling and the higher uniformity in plant growth and development during the crop cycle. This work was carried out aiming to quantify the effects of plant population increment on the leaf area, grain yield and the variation coefficient of agronomic traits of maize cultivars with contrasting genetic variability. The trial was set in Lages, SC, Brazil. A randomized block experimental design disposed in split-plots was used. Three cultivars were evaluated in the main plot: an open-pollinated variety (Fortuna), a double-cross hybrid (Ag 303) and a single-cross hybrid (P30F53). Five plant populations were tested in the split-plot: 25,000, 50,000, 75,000, 100,000, and 125,000 plants ha-1. The experiment was sowed on 10-26-2005, with a row spacing of 0.70 m. When the crop had four expanded leaves, 10 plants of each split-plot that were in the same growth stage were labeled. These plants were used to measure leaf area and to follow the crop growth, determining the variation coefficient of leaf area, growth stage and plant height. These variables were estimated 10 times, at the growth stages of V4, V8, V12, V16, R1 (silking) and 14, 28, 42, 56 and 70 days after silking. After harvesting, the variation coefficient and grain production per plant were determined based on the 10 selected plants. In addition to that, grain production and yield components were determined. The data were submitted to the variance analysis by the F test, at the 5.0% significance level (P<0.05). The means were compared by the Tukey s test (P<0.05), by polynomial regression and linear correlation. The response of grain yield to increment in plant population was quadratic, regardless of cultivar. Grain yield of the singlecross hybrid (SCH) was higher and more responsive to increase in plant density than grain yield of the double-cross hybrid (DCH) and the open-pollinated variety (OPV). The plant densities that optimized grain yield were 86,665 plants ha-1, 53,044 plants ha-1 and 85,000 plants ha-1 for the SCH, DCH and OPV, respectively. The SCH presented higher leaf area values than the other cultivars 56 days after silking, when plant populations greater than 50,000 plants ha-1 were used. The highest variation coefficient value for grain production per plant was registered at 125,000 plants ha-1 and the lowest at 25,000 plants ha-1. The SCH presented smaller variation coefficient than the DCH and OPV for plant height and leaf area at silking, and for grain yield per plant. The higher morphologic uniformity of the SCH probably contributed to reduce intra-specific competition for water, light and nutrients, establishing a stronger sink after flowering. The SCH greater demand for photosynthetic products possibly favored the maintenance of leaf activity for a higer period, delaying senescence. Therefore, the slower leaf senescence and the more uniform plant growth contributed to the SCH higher grain yield and to the higher productivity differences between the SCH and the other two cultivars in the highest plant densities (75,000, 100,000 e 125,000 plants ha-1)
O incremento na densidade de plantas é uma forma de maximizar a interceptação da radiação solar e o rendimento de grãos do milho. Contudo, ele também pode reduzir a atividade fotossintética da planta e a eficiência de conversão dos fotoassimilados à produção de grãos. Aumentos na tolerância de híbridos de milho ao adensamento têm sido reportados em diferentes regiões produtoras no mundo. Duas características que podem contribuir para isto são a senescência foliar mais lenta no enchimento de grãos e a maior uniformidade no crescimento e desenvolvimento das plantas durante o ciclo da cultura. Este trabalho foi conduzido com os objetivos de quantificar o efeito do incremento da população de plantas sobre a área foliar, o rendimento de grãos e o coeficiente de variação de características agronômicas de cultivares de milho com bases genéticas contrastantes. O experimento foi conduzido no município de Lages-SC. O delineamento experimental utilizado foi o de blocos casualizados dispostos em parcelas subdivididas. Na parcela principal foram testadas três cultivares de milho: uma variedade de polinização aberta (Fortuna), um híbrido duplo (Ag303) e um híbrido simples (P30F53). Cinco populações de plantas foram avaliadas nas subparcelas: 25.000, 50.000, 75.000, 100.000 e 125.000 plantas ha-1. O experimento foi implantado no dia 26 de outubro de 2005, com espaçamento entre linhas de 0,70 m. Quando a cultura estava com quatro folhas expandidas, marcou-se 10 plantas de cada subparcela que estivessem no mesmo estádio fenológico. Estas plantas foram utilizadas para as avaliações de área foliar, bem como para o acompanhamento do crescimento, determinando-se o coeficiente de variação para área foliar, estádio fenológico e estatura de planta. Estas variáveis foram avaliadas 10 vezes, nos estádios V4, V8, V12, V16, R1 (espigamento) e aos 14, 28, 42, 56 e 70 dias após o espigamento. Após a colheita, foram determinados o coeficiente de variação e a produção de grãos por planta, nas 10 plantas selecionadas. Além disso, determinou-se a produção de grãos na área útil, bem como os componentes do rendimento. Os dados foram submetidos à análise de variância pelo teste F, ao nível de significância de 5% (P<0,05). As médias foram analisadas pelo teste de Tukey, a 5% de probabilidade de erro (P<0,05), por regressão polinomial e por correlação linear. A reposta do rendimento de grãos das três cultivares ao incremento na densidade de plantas foi quadrática. O rendimento de grãos do híbrido simples (HS) foi maior e mais responsivo ao incremento na população de plantas do que o híbrido duplo (HD) e da variedade de polinização aberta (VPA). As populações que otimizaram o rendimento de grãos foram de 86.665 plantas ha-1, 53.044 plantas ha-1 e 85.000 plantas ha-1 para o HS, HD e VPA, respectivamente. O HS apresentou maior valor de área foliar do que as demais cultivares aos 56 dias após o espigamento, nas densidades superiores a 50.000 plantas ha-1. Os maiores coeficientes de variação para produção de grãos por planta foram obtidos na densidade de 125.000 plantas ha-1 e os menores na de 25.000 plantas ha-1. O HS apresentou menor coeficiente de variação do que o HD e a VPA para estatura de planta e área foliar no espigamento, bem como para produção de grãos por planta. As maiores uniformidades morfológica e fenológica do HS provavelmente contribuiu para reduzir a competição intra-específica por água, luz e nutrientes, favorecendo o estabelecimento de um dreno mais forte logo após a floração. A maior demanda por fotoassimilados do HS possivelmente favoreceu a manutenção da atividade fotossintética das folhas por um período mais longo, retardando a senescência foliar. Portanto, a senescência foliar mais lenta e o desenvolvimento uniforme das plantas contribuíram para o maior rendimento de grãos do HS e para as maiores diferenças de produtividade registradas entre o HS e o HD e a VPA nas densidades mais altas (75.000, 100.000 e 125.000 plantas ha-1)
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48

Gascoigne-Owens, Johanna Sara. "Responses of the Câ‚„ plant Zea mays (maize) to elevated atmospheric carbon dioxide concentration." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414631.

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49

Ukeh, Donald A. "The identification and use of semiochemicals for the control of the maize weevil, Sitophilus zeamais (Motschulsky) in Nigeria." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25167.

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50

Carroll, David A. "Drought and Nitrogen Effects on Maize Canopy Temperature and Stress Indices." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5932.

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Increased water scarcity due to changing climate, population growth, and economic development is a major threat to the sustainability of irrigated agriculture in the Western United States and other regions around the world. Management practices, such as controlled deficit irrigation, that seek to maximize the productivity of a limited water supply are critical. When using controlled deficit irrigation, remote sensing of crop canopy temperature is a useful tool for assessing crop water status and for more precise irrigation management. However, there is potential that nutrient deficiencies could compound the interpretation of water status from leaf temperature by altering leaf color and radiation balance. One objective of this thesis was to evaluate whether nitrogen fertility status of maize interacts with remotely sensed leaf temperature under full and limited irrigation. Another objective was to evaluate the effect of varying irrigation and nitrogen regimes on three water stress indices: Crop Water Stress Index (CWSI), Degrees Above Non-Stressed (DANS), and Degrees Above Canopy Threshold (DACT). Replicated studies were conducted using maize grown in both the glasshouse and the field. The glasshouse study consisted of combinations of well-watered and drought irrigation and sufficient and deficient nitrogen levels, while the field study consisted of combinations of well-watered, limited or controlled deficit, and drought irrigation and sufficient, sufficient delayed, and deficient nitrogen levels. In the glasshouse, leaf chlorophyll content was reduced moderately by limited irrigation and more so by N deficiency. For most observations in the glasshouse, the remotely sensed leaf temperatures were affected by irrigation, but not by N level. With drought irrigation, leaf temperature averaged 29.0° C, compared to 27.9 °C for the well-watered treatment. Similar results were observed in the field, illustrating the utility of canopy temperature in detecting water stress and that the measurement was not confounded by N status. It was also found that irrigation had a significant effect on all three water stress indices. For example, in the glasshouse, cumulative DANS was 32.2 for the drought treatment and 15.5 for the well-watered treatment. Similar results were found for other stress index measurements both in the glasshouse and the field. DANS underestimated stress on days when the reference crop was stressed and overestimated stress on low temperature days. DACT risks finding no stress when temperatures are below the canopy threshold temperature of 28.0 °C. Thus, CWSI is the most effective index, given that it takes humidity and air temperature into account. Indices were only weakly related to leaf area, biomass or grain yield, or crop water productivity. Linear regression of Nitrogen Sufficiency Index and its effect on crop growth found significant effects on biomass and grain yield, crop water productivity, and final leaf area. Thus, water stress indices are useful tools in evaluating crop water status, but consideration of other factors, such as nutrient status, must be taken for prediction of crop growth and yield.
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