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Correction For Rapid-Growth Vegetation And Testing Of An Upscaling Method With A Cosmos Probe, Samantha Lou Irvin Jan 2013

Correction For Rapid-Growth Vegetation And Testing Of An Upscaling Method With A Cosmos Probe, Samantha Lou Irvin

Graduate Theses and Dissertations

COSMOS (COsmic-ray Soil Moisture Observing System) probes are a developing instrument in the field of remote sensing and are currently the only source of field scale soil moisture data. A COSMOS probe is essentially a hydrogen particle counter with a measurement depth ranging from 10-70 cm and a spatial resolution approaching 700 m in diameter. A majority of the hydrogen detected is in the form of water molecules. As vegetation contains both hydrogen in the vegetative dry matter and water, in addition to sitting above the ground, it may influence what is measured by the COSMOS probe as soil moisture ...


Sooty Blotch And Flyspeck Disease Of Apple: Expansion Of The Fungal Complex In Turkey And Evaluation Of A Warning System For The Upper Midwest, Derrick Anthony Mayfield Jan 2013

Sooty Blotch And Flyspeck Disease Of Apple: Expansion Of The Fungal Complex In Turkey And Evaluation Of A Warning System For The Upper Midwest, Derrick Anthony Mayfield

Graduate Theses and Dissertations

Sooty blotch and flyspeck (SBFS) is a disease complex caused by nearly 80 fungal species that blemish the surface of apple fruit, reducing crop value in humid regions worldwide. The severity of SBFS is a concern for apple producers in northeastern Turkey. However, the composition of the SBFS complex in Turkey is unknown. Therefore, the first objective of my research was to isolate and characterize the species assemblage from SBFS infected apples collected in 2008 from the Rize Province, in Turkey. In this study, pressed SBFS colonies with subtending apple cuticle were shipped to Iowa State University for isolation. The ...


Investigation Of The Arabidopsis Nonhost Resistance Mechanism Against The Soybean Pathogen, Phytophthora Sojae, Rishi Sumit Jan 2013

Investigation Of The Arabidopsis Nonhost Resistance Mechanism Against The Soybean Pathogen, Phytophthora Sojae, Rishi Sumit

Graduate Theses and Dissertations

Nonhost resistance (NHR) provides immunity to all members of a plant species against all isolates of a microorganism that is pathogenic to other plant species. Three Arabidopsis thaliana PEN (penetration deficient) genes, PEN1, 2 and 3 have been shown to provide prehaustorial NHR against the barley pathogen Blumeria graminis f. sp. hordei. Arabidopsis pen1-1 mutant is penetrated by the hemibiotrophic oomycete pathogen, Phytophthora sojae that causes root and stem rot disease in soybean. The P. sojae susceptible (pss) 1 mutant is infected by both P. sojae and the hemibiotrophic fungal pathogen, Fusarium virguliforme that causes sudden death syndrome in soybean ...


Identification And Characterization Of Effectors Secreted From Sedentary Endoparasitic Phytonematodes, William Brock Rutter Jan 2013

Identification And Characterization Of Effectors Secreted From Sedentary Endoparasitic Phytonematodes, William Brock Rutter

Graduate Theses and Dissertations

Sedentary endoparasitic phytonematodes are a group of taxa comprised of cyst nematodes (Heterodera and Globodera spp.) and root-knot nematodes (Meloidogyne spp. ), which are some of the most economically important crop pathogens on earth. These pests infect plant roots by creating elaborate feeding sites around the vasculature, which diverts nutrients away from the plant to feed the nematode and causes yield reduction in the plant. The nematodes create their feeding sites by delivering effector proteins into plant tissues. Effectors interact with plant components to modify development, metabolism, and defense pathways within plant cells, ultimately forming and maintaining the feeding site within ...


Biochar As A Replacement For Perlite In Greenhouse Soilless Substrates, Jake Northup Jan 2013

Biochar As A Replacement For Perlite In Greenhouse Soilless Substrates, Jake Northup

Graduate Theses and Dissertations

Biochar is a solid, carbonaceous coproduct of the pyrolysis process used for biofuel production. Many field studies have shown improved chemical and physical properties of soil after amendment with biochar. The benefits of biochar may extend to soilless substrates used in the greenhouse industry, and the porous nature of biochar may make it a suitable replacement for perlite in greenhouse substrates. The objectives of this research were to determine the most suitable biochar particle size and percentage for use in a greenhouse substrate, to determine if biochar can eliminate the need for amendment with limestone, and to demonstrate plant growth ...


Characterization Of A Cell Death Suppressing Effector Broadly Conserved Across The Fungal Kingdom, Ehren Lee Whigham Jan 2013

Characterization Of A Cell Death Suppressing Effector Broadly Conserved Across The Fungal Kingdom, Ehren Lee Whigham

Graduate Theses and Dissertations

The proteins used by pathogens to modify, suppress or evade host defenses (called effectors) are fascinating probes into plant defense pathways and are changing the way scientists think about host/pathogen interactions. Blumeria graminis f. sp. hordei, causal agent of barley powdery mildew disease, is a model system to study the nature of obligate biotrophy. In addition to the nearly 500 predicted effector candidates unique to the mildews, this pathogen contains at least one that is broadly conserved across the fungal kingdom. Understanding the functions and targets of both the unique and conserved effectors has the potential to reveal new ...


The Effects Of Starter Fertilizer On Root And Shoot Growth Of Corn Hybrids And Seeding Rates And Plant-To-Plant Variability In Growth And Grain Yield, Warren Pierson Jan 2013

The Effects Of Starter Fertilizer On Root And Shoot Growth Of Corn Hybrids And Seeding Rates And Plant-To-Plant Variability In Growth And Grain Yield, Warren Pierson

Graduate Theses and Dissertations

Starter fertilizer often increases early-season growth of corn; however, yield responses have varied. Yield responses often occur on soils with low soil fertility, however, have occurred on soils with high fertility. Currently, farmers are attempting to reduce plant-to-plant variability in growth and development to maximize grain yield. Farmers have asked if placing starter fertilizer near the seed could reduce plant-to-plant variability with the hypothesis that uniform fertility will result in uniform plants. We conducted two experiments near Ames, Iowa, and Nashua, Iowa with similar treatments and data collection. Starter fertilizer was banded 5 cm below the seed and 5 cm ...


An Investigation Of The Factors Leading To Invasion Success Of Non-Native Plants Using A System Of Native, Introduced Non-Invasive, And Invasive Eugenia Congeners In Florida, Kerry Bohl Jan 2013

An Investigation Of The Factors Leading To Invasion Success Of Non-Native Plants Using A System Of Native, Introduced Non-Invasive, And Invasive Eugenia Congeners In Florida, Kerry Bohl

Graduate Theses and Dissertations

The overwhelming majority of plant species introduced into a new range never become invasive. Consequently, identification of factors allowing the small fraction of successful invaders to naturalize, increase in abundance, and displace resident species continues to be a key area of research in invasion biology. Of the considerable number of hypotheses that have been proposed to resolve why some plant species become noxious pests, the enemy release hypothesis (ERH) is one of the most commonly cited. The ERH maintains that invasive plants succeed in a new range because they are no longer regulated by their coevolved natural enemies, and this ...


Chlorophyll Fluorescence And Thermal Stress In Archaias Angulatus (Class Foraminifera), Heidi M. Toomey Jan 2013

Chlorophyll Fluorescence And Thermal Stress In Archaias Angulatus (Class Foraminifera), Heidi M. Toomey

Graduate Theses and Dissertations

ABSTRACT

Benthic foraminifers that host algal symbionts are similar to corals in that they rely on their algal endosymbionts for their energy needs, calcify prolifically, and are sensitive to changes in environmental conditions. They are abundant in the benthos of coastal coral-reef areas and are found throughout the tropical and subtropical regions. Pulse Amplitude Modulated (PAM) chlorophyll fluorometry and chlorophyll a extraction techniques were used to quantify and compare the photosynthetic responses of the benthic foraminiferal, Archaias angulatus and their isolated endosymbionts, Chlamydomonas hedleyi, to short-term changes in temperature. Maximum quantum efficiency (Fv/Fm) and rapid light curves ...


Effect Of Corn Stover Harvest And Winter Rye Cover Crop On Corn Nitrogen Fertilization, Jose L. Pantoja Jan 2013

Effect Of Corn Stover Harvest And Winter Rye Cover Crop On Corn Nitrogen Fertilization, Jose L. Pantoja

Graduate Theses and Dissertations

Improvement in N management to optimize corn N fertilization requirement and minimize NO33--N loss from agricultural fields is an ongoing need for continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr.] production systems. This is especially important in Iowa as this state has the largest corn production across the U.S.A. The present dissertation includes two projects that evaluated corn response to N application and optimal fertilization rate. The first project evaluated the effect of corn stover harvest (SH) in continuous corn and the interaction with chisel plow and no-tillage systems; and the second project ...


Density Response Of Maize Canopy Architecture In Adapted And Unadapted Synthetic Populations, Naser Bader Alkhalifah Jan 2013

Density Response Of Maize Canopy Architecture In Adapted And Unadapted Synthetic Populations, Naser Bader Alkhalifah

Graduate Theses and Dissertations

ABSTRACT

Since the 1950's, the average maize grain yield, on a per unit area basis, has risen exponentially and without a pause. Associated with this increase have been changes in shoot morphology which permit more light penetration into the canopy. Changes in plant traits including plant height, leaf number, individual leaf area, vertical leaf angle, tassel size and weight, and leaf area density distribution along the main stem have been reported in the literature; however, the response of canopy components to changes in plant density has not been examined in closed populations and at today's densities. The objective ...


Hybrid Breeding In Perennial Grasses Based On Self-Incompatibility And Self-Fertility, Andrea Sofia Arias Aguirre Jan 2013

Hybrid Breeding In Perennial Grasses Based On Self-Incompatibility And Self-Fertility, Andrea Sofia Arias Aguirre

Graduate Theses and Dissertations

For a long time, petroleum-based fuels have been used to provide energy, but limited supplies along with environmental effects of fossil fuels created the need of alternative and clean energy sources. Grasses in general have a low lignin content compared to woody species which is desirable for ethanol production. Furthermore, other features such as: low water and nutrient requirements, and a high rate of carbon fixation that make grasses desirable for biomass production. Perennial grasses have also environmental advantages such as reduced soil organic matter and tillage requirements compared with annual species. Perennial ryegrass has been increasingly used in Europe ...


Candidate Gene Based Association Study For Nitrogen Use Efficiency And Associated Traits In Maize, Bharath Kumar Thamasandra Narayana Jan 2013

Candidate Gene Based Association Study For Nitrogen Use Efficiency And Associated Traits In Maize, Bharath Kumar Thamasandra Narayana

Graduate Theses and Dissertations

Nitrogen (N) is a major macronutrient used in cereal production that stimulates plant growth and development. Demand for N fertilizer has been growing steadily at an annual growth rate of 1.8 percent due to the continuous increase in the cereal growing areas (mainly maize), and N is needed to maximize yield potential of agricultural crops. It has been estimated that N fertilizer used by cereals is only 33%. The rest of the applied N fertilizer is lost in the combination of surface runoff, gaseous release from soil, leaching and de-nitrification processes. In the future, for a sustainable crop production ...


Studies On Extraction And Control Of Plant-Parasitic Nematodes On Corn, Mychele Batista Da Silva Jan 2013

Studies On Extraction And Control Of Plant-Parasitic Nematodes On Corn, Mychele Batista Da Silva

Graduate Theses and Dissertations

Some plant-parasitic nematodes exist within root tissue and must be extracted from the roots to identify and count them. However, efficiency comparisons of methods and solutions have not been published. We have tested if water is a better extraction solution than mercuric chloride-dihydrostreptomycin sulfate for recovery of lance and root-lesion nematodes in corn roots. Also, we have tested if the platform shaker method is more effective than the Baermann funnel for extracting these nematodes and if there is an interaction between extraction solution and extraction method in recovery of these nematodes from corn roots. In addition, we infected corn roots ...


Evaluation And Prediction Of Corn Stover Biomass And Composition From Commercially Available Corn Hybrids, Ty Jason Barten Jan 2013

Evaluation And Prediction Of Corn Stover Biomass And Composition From Commercially Available Corn Hybrids, Ty Jason Barten

Graduate Theses and Dissertations

ABSTRACT

High consumption of imported energy in the United States and other countries has increased the interest in bio-renewable sources of energy. This interest has fueled research into crop residues as one potential alternative fuel source. At issue is how to balance economic viability with the sustainability of the endeavor.

The objective of this project was two-fold. The first objective was to quantify the amount and distribution of dry matter, moisture, fiber, and minerals in corn stover from a number of corn hybrids, grown at varying population densities. In this multi-year study we found that of the stover material remaining ...


Investigating The Evolution Of Cytochromes P450 Involved In Ga Biosynthesis, Sibongile Mafu Jan 2013

Investigating The Evolution Of Cytochromes P450 Involved In Ga Biosynthesis, Sibongile Mafu

Graduate Theses and Dissertations

Vascular plants invariably contain a class II diterpene cyclase (EC 5.5.1.x), as an ent-copalyl diphosphate synthase is required for gibberellin phytohormone biosynthesis. This has provided the basis for evolution of a functionally diverse enzymatic family. A bifunctional diterpene synthase was characterized from the lycophyte Selaginella moellendorffii . The structure of its product, labda-7,13E-dien-15-ol, demonstrates that this enzyme catalyzes a novel class II diterpene cyclization reaction, and clarifies the biosynthetic origins of the family of derived natural products.

All higher plants contain kaurene oxidases (KO), which are multifunctional cytochromes P450 that catalyze oxidation at the C4α methyl, converting ...


Computational And Experimental Analysis Of Tal Effector-Dna Binding, Erin Lynn Doyle Jan 2013

Computational And Experimental Analysis Of Tal Effector-Dna Binding, Erin Lynn Doyle

Graduate Theses and Dissertations

TAL effectors, from the plant-pathogenic bacterial genus Xanthomonas, are DNA binding proteins that can be engineered to bind to almost any sequence of interest. The DNA target of the TAL effector is encoded by a modular central repeat region, with each repeat specifying a single binding site nucleotide. TAL effectors can be targeted to novel DNA sequences by assembling the corresponding repeat sequence. Therefore, custom TAL effectors have become important tools for manipulating gene expression and creating site-specific DNA modifications. This dissertation explores TAL effector-DNA binding through computational and experimental analyses.

I identified positional and composition biases in known TAL ...


Association Mapping Analysis For Brassinosteroid Candidate Genes And Plant Architecture In A Diverse Sorghum Bicolor Panel, Maria Betsabe Mantilla Perez Jan 2013

Association Mapping Analysis For Brassinosteroid Candidate Genes And Plant Architecture In A Diverse Sorghum Bicolor Panel, Maria Betsabe Mantilla Perez

Graduate Theses and Dissertations

Sorghum bicolor (L) Moench is a cultivated and self-pollinated species used traditionally for human consumption, livestock feed and forage production. Recently, sorghum has received attention as a bioenergy crop because of its high water use efficiency, yield biomass potential and biomass composition. To develop superior sorghum inbred lines for bioenergy production, it would be beneficial to understand the genetic mechanisms controlling plant architecture traits. Sorghum presents a remarkable diversity in the species bicolor that can be exploited to identify new genes associated with those traits of interest. Brassinosteroids (BR) are steroid hormones that control different aspects of plant growth and ...


Genomic And Genetic Studies Of Environmental Control Of Brachypodium Growth And Development, Ying Feng Jan 2013

Genomic And Genetic Studies Of Environmental Control Of Brachypodium Growth And Development, Ying Feng

Graduate Theses and Dissertations

Brachypodium distachyon has recently been established as a model for cereals and temperate grasses because of its sequenced small genome (~270M), a small stature, short life cycle, self-fertility, an efficient transformation system and particularly its diverse ecotypes. Determination of the function for each gene in the Brachypodium genome is urgently needed for utilization of this species. In this study we (1) analyze the expression of each gene involved in vernalization pathway in Brachypodium and the correlation of vernalization requirement with freezing tolerance, (2) develop a novel high-throughput RNAi method, Phi29-Amplified RNAi Construct (PARC), to construct a cold-specific RNA interference library ...


Bacterial Wilt Of Cucurbits: Ecology, Genetics, And Management, Erika Saalau Rojas Jan 2013

Bacterial Wilt Of Cucurbits: Ecology, Genetics, And Management, Erika Saalau Rojas

Graduate Theses and Dissertations

Bacterial wilt of cucurbits is an economically important disease that impacts most Cucurbitaceae species. The pathogen, Erwinia tracheiphila, is a vascular-inhabiting bacterium overwintered and transmitted by cucumber beetles. Disease management relies on controlling cucumber beetles, mainly through insecticide applications. However, the ecology and biology of E. tracheiphila are poorly understood. A better understanding of this pathosystem is critical for the development of effective and less insecticide-intensive management strategies.

Six field experiments were carried out to accomplish the following objectives: 1) assess efficacy of delayed removal of spunbond row covers for suppressing bacterial wilt on muskmelon, and 2) compare costs and ...


Investigation Of Genes Involved In The Formation Of Nitrogen-Fixing Nodules In Soybean, Chichun Yang Jan 2013

Investigation Of Genes Involved In The Formation Of Nitrogen-Fixing Nodules In Soybean, Chichun Yang

Graduate Theses and Dissertations

Nodulation is an important process in legume-rhizobium symbiotic nitrogen fixation. This thesis demonstrates our investigation of genes involved in soybean nodulation.

In the first project, we studied the molecular mechanisms contributing to an abnormal-nodulation phenotype of a soybean T-DNA insertion mutant, 454-4. Genetic analysis showed that T-DNAs are integrated into two loci of 454-4 genome, nodulation signaling pathway 2 (GmNSP2a), and GmEREACTA. Since GmNSP2a is orthologous to NSP2 proteins from Medicago truncatula and Lotus japonicus that are essential for nodulation, we speculated that the abnormal nodulation phenotype of 454-4 is due to the T-DNA insertions at GmNSP2a. To test it ...


Corn Yield Variability On The Des Moines Lobe Of Iowa: Assessment Of Extent And Soil-Related Causes, Matthew Thomas Streeter Jan 2013

Corn Yield Variability On The Des Moines Lobe Of Iowa: Assessment Of Extent And Soil-Related Causes, Matthew Thomas Streeter

Graduate Theses and Dissertations

Precision agriculture techniques are an essential component to modern row crop agriculture in Iowa and can be used to create crop yield variability maps via geographic information systems. The first objective of this thesis was to explore the methodology that could be used to locate significant long-term corn yield variability on the Iowa Des Moines Lobe. A 158-ha site, consisting mainly of Clarion, Nicollet and Webster soil map units and containing multiple years of geo-referenced corn (Zea mays) yield data was selected. A cluster analysis tool was performed to locate spatially consistent corn yield variability (high, low and mean yield ...


Controlling Biomass Properties For Optimizing Fast Pyrolysis Products, Brandon Jeffrey Jan 2013

Controlling Biomass Properties For Optimizing Fast Pyrolysis Products, Brandon Jeffrey

Graduate Theses and Dissertations

The energy future of the United States is likely to include a large number of traditional and alternative energy sources and technologies. Fast pyrolysis has been identified as one of the alternative energy conversion processes that could play a role in this energy future. Fast pyrolysis produces solid (biochar), liquid (bio-oil), and gaseous products (syngas). Bio-oil is the main component (up to 80%) and has a number of potentially useful applications. Bio-oil composition is complex and is related to cell wall composition, as compounds in the bio-oil derive from the individual cell wall components cellulose, hemicelluloses, and lignin.

While a ...


Physiology Of Genotype X Soil Fertility Effects On Yield And Accumulation Of Iron And Zinc In The Common Bean (Phaseolus Vulgaris L.) Seed, Gerald Sebuwufu Jan 2013

Physiology Of Genotype X Soil Fertility Effects On Yield And Accumulation Of Iron And Zinc In The Common Bean (Phaseolus Vulgaris L.) Seed, Gerald Sebuwufu

Graduate Theses and Dissertations

This thesis research focused on evaluating improved common bean (Phaseolus vulgaris L.) germplasm under intensified fertility regimes, and assessing how assimilate partitioning to the seed impacts seed mineral concentration. In Chapter 2, the agronomic performance of four improved varieties was evaluated on small-landholder farms using locally available manure and typical farming practices. Only one of the improved varieties, K131, yielded significantly more than the local check, Kanyebwa. Use of locally available manure significantly increased yields, but they remained less than 50% of the potential yield of improved varieties as demonstrated by the experiment station. Among resource limited farmers, options for ...


Enhancing Biological Nitrogen Fixation In Common Bean (Phaseolus Vulgaris L), Mercy Kasuzi Kabahuma Jan 2013

Enhancing Biological Nitrogen Fixation In Common Bean (Phaseolus Vulgaris L), Mercy Kasuzi Kabahuma

Graduate Theses and Dissertations

Common bean (Phaseolus vulgaris L.) is a herbaceous annual which, in a symbiotic relationship with specific soil bacteria, `fixes' atmospheric nitrogen (N 2) into amino form that can be used for plant growth. Efforts to optimize biological nitrogen fixation (BNF) in common beans are critical because of widespread increase in soil degradation in Africa. Among legumes, common beans derive the least percent N 2 from N2 fixation. This has been attributed partly to susceptibility of common beans to physical and chemical environmental stresses, inconsistent response to inoculum, and lack of selection for the BNF trait. Improvement in productivity of ...