Digital Commons Network^™

Effect Of Temperature On Wheat Streak Mosaic Disease Development In Winter Wheat, Everlyne N. Wosula, Satyanarayana Tatineni, Stephen N. Wegulo, Gary L. Hein

Department of Plant Pathology: Faculty Publications

Temperature is one of the key factors that influence viral disease development in plants. In this study, temperature effect on Wheat streak mosaic virus (WSMV) replication and in planta movement was determined using a green fluorescent protein (GFP)-tagged virus in two winter wheat cultivars. Virus-inoculated plants were first incubated at 10, 15, 20, and 25°C for 21 days, followed by 27°C for 14 days; and, in a second experiment, virus-inoculated plants were initially incubated at 27°C for 3 days, followed by 10, 15, 20, and 25°C for 21 days. In the first experiment, WSMV-GFP in susceptible ‘Tomahawk’ wheat at 10°C …

Detection And Characterization Of Xanthomonas Vasicola Pv. Vasculorum (Cobb 1894) Comb. Nov. Causing Bacterial Leaf Streak Of Corn In The United States, J. M. Lang, E. Ducharme, J. Ibarra Caballero, E. Luna, T. Hartman, M. Ortiz-Castro, K. A. Korus, J. Rascoe, T. A. Jackson-Ziems, K. Broders, J. E. Leach

Department of Plant Pathology: Faculty Publications

Bacterial leaf streak of corn (Zea mays) recently reached epidemic levels in three corn-growing states and has been detected in another six states in the central United States. Xanthomonas vasicola was identified as the causal agent of this disease. A multilocus sequence alignment of six housekeeping genes and comparison of average nucleotide identity from draft genome sequence were used to confirm phylogenetic relationships and classification of this bacteria relative to other X. vasicola strains. X. vasicola isolates from Nebraska and South Africa were highly virulent on corn and sugarcane and less virulent on sorghum but caused water-soaking symptoms …

Plant Disease Management, Tamra A. Jackson-Ziems, Anthony O. Adesemoye, Loren J. Giesler, Robert M. Harveson, Stephen N. Wegulo, Joshua J. Miller, James D. Harbour

Department of Plant Pathology: Faculty Publications

Fungicides are an important component of the pesticide program for some Nebraska fields. While not all fields of corn, dry bean, sorghum, soybean, sugarbeet, sunflower, and wheat will require a fungicide application, it’s critical that you know the correct product for the disease in your field when you do need it.

Identification. The first step with any disease management program is to make sure you have correctly identified the problem. Identification is critical as there are many bacterial diseases with symptoms similar to fungal diseases, and fungicides will have no activity on them. For help identifying crop diseases, visit the …

What's New In Plant Pathology, Joshua J. Miller, Anthony O. Adesemoye, Loren Giesler, Robert M. Harveson, Tamra A. Jackson-Ziems, Stephen N. Wegulo, James D. Harbour, Terra Hartman

Department of Plant Pathology: Faculty Publications

Changes to the Disease Management Section of the 2017 Guide for Weed, Disease, and Insect Management in Nebraska

Bacterial Leaf Streak of Corn—An Emerging Disease in Nebraska and First Report in the United States

Pest and Plant Diagnostic Clinic Position Change

New Products … Ethos XB … Majestene

Table 1. Foliar products for disease control that were updated in the 2017 Guide for Weed, Disease, and Insect Management in Nebraska

Table 2. Seed treatment products for disease control that were updated in the 2017 Guide for Weed, Disease, and Insect Management in Nebraska

Table 3. Biological products that were updated …

Response Of Sorghum Stalk Pathogens To Brown Midrib Plants And Soluble Phenolic Extracts From Near Isogenic Lines, Deanna L. Funnell-Harris, Patrick M. O'Neill, Scott E. Sattler, Tammy Gries, Mark A. Berhow, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Sorghum [Sorghum bicolor (L.) Moench] has drawn attention as potential feedstock for lignocellulosic biofuels production, and reducing lignin is one way to increase conversion efficiency. Little research has been previously conducted to assess the response of reduced lignin sorghum lines to the Fusarium stalk rot pathogens Fusarium verticillioides and Fusarium proliferatum and the charcoal rot pathogen, Macrophomina phaseolina. Loss of function mutations in either the Brown midrib (Bmr) 6 or 12 gene that both encode a monolignol biosynthetic enzyme in the pathway that produces subunits of the lignin polymer, results in reduced lignin content. Near-isogenic bmr6, …

Best Practices For Population Genetic Analyses, Niklaus J. Grünwald, Sydney E. Everhart, B. J. Knaus, Z. N. Kamvar

Department of Plant Pathology: Faculty Publications

Population genetic analysis is a powerful tool to understand how pathogens emerge and adapt. However, determining the genetic structure of populations requires complex knowledge on a range of subtle skills that are often not explicitly stated in book chapters or review articles on population genetics. What is a good sampling strategy? How many isolates should I sample? How do I include positive and negative controls in my molecular assays? What marker system should I use? This review will attempt to address many of these practical questions that are often not readily answered from reading books or reviews on the topic, …

Phenotypic And Genotypic Characterization Of Relevant Sclerotinia Sclerotiorum Isolates, Thomas J. Justo Miorini, Anthony G. Pannullo, T. Hornby, Robert Higgins, Sydney E. Everhart, James R. Steadman

Department of Plant Pathology: Faculty Publications

Knowledge of pathogen population structure is useful to identify isolates for screening cultivars and lines for resistance. For S. sclerotiorum, causal agent of white mold in more than 400 plant species, including common bean and soybean, breeding for resistance is particularly challenging. The objective of this study was to characterize phenotypic and genotypic variation of S. sclerotiorum isolates from soybean production areas of the U.S.A. (15), Brazil (75), and Argentina (5) to compare them with 366 isolates from dry bean characterized previously (Everhart et al., 2016).

Best Practices For Population Genetic Analyses, Niklaus J. Grünwald, Sydney E. Everhart, B. J. Knaus, Zhian N. Kamvar

Department of Plant Pathology: Faculty Publications

Population genetic analysis is a powerful tool to understand how pathogens emerge and adapt. However, determining the genetic structure of populations requires complex knowledge on a range of subtle skills that are often not explicitly stated in book chapters or review articles on population genetics. What is a good sampling strategy? How many isolates should I sample? How do I include positive and negative controls in my molecular assays? What marker system should I use? This review will attempt to address many of these practical questions that are often not readily answered from reading books or reviews on the topic, …

Control Of White Mold Of Dry Bean And Residual Activity Of Fungicides Applied By Chemigation, Thomas J.J. Miorini, Carlos G. Raetano, Sydney E. Everhart

Department of Plant Pathology: Faculty Publications

Sclerotinia sclerotiorum is a necrotrophic fungal pathogen that causes white mold of dry bean (Phaseolus vulgaris L.). Chemigation with fungicides is used for disease control, but effectiveness of this application method and impact of irrigation level on residual fungicide activity in the plant over time under field conditions has not been well characterized. To assess the best method of application and fungicide for disease control, we conducted field studies in three field sites in São Paulo State in Brazil. Contact fungicide, fluazinam, was applied via center pivot at three irrigation levels (2.5, 5.1, 10.1 mm) at the Itaí field …

Structure Of The N-Glycans From The Chlorovirus Ne-Jv-1, Immacolata Speciale, Irina Agarkova, Garry Duncan, James L. Van Etten, Cristina De Castro

James Van Etten Publications

Results from recent studies are breaking the paradigm that all viruses depend on their host machinery to glycosylate their proteins. Chloroviruses encode several genes involved in glycan biosynthesis and some of their capsid proteins are decorated with N-linked oligosaccharides with unique features. Here we describe the elucidation of the N-glycan structure of an unusual chlorovirus, NE-JV-1, that belongs to the Pbi group. The host for NE-JV-1 is the zoochlorella Micractinium conductrix. Spectroscopic analyses established that this N-glycan consists of a core region that is conserved in all of the chloroviruses. The one difference is that the residue 3OMe-l-rhamnose is …

Glucose-Abl1-Tor Signaling Modulates Cell Cycle Tuning To Control Terminal Appressorial Cell Differentiation, Margarita Marroquin-Guzman, Guangchao Sun, Richard Wilson

Department of Plant Pathology: Faculty Publications

The conserved target of rapamycin (TOR) pathway integrates growth and development with available nutrients, but how cellular glucose controls TOR function and signaling is poorly understood. Here, we provide functional evidence from the devastating rice blast fungus Magnaporthe oryzae that glucose can mediate TOR activity via the product of a novel carbon- responsive gene, ABL1, in order to tune cell cycle progression during infection-related development. Under nutrient-free conditions, wild type (WT) M. oryzae strains form terminal plant-infecting cells (appressoria) at the tips of germ tubes emerging from three-celled spores (conidia). WT appressorial development is accompanied by one round …

Phytophthora Sojae Infecting Soybean: Pathotype Diversity, New Sources Of Resistance And Interaction With The Soybean Cyst Nematode, Rawnaq Nazneen Chowdhury

Electronic Theses and Dissertations

Phytophthora root and stem rot, caused by Phytophthora sojae Kaufmann and Gerdemann, is an important disease of soybean (Glycine max L.) in South Dakota. To gain a better understanding of the importance of P. sojae in South Dakota, specifically pathotype diversity, identification of new resistance sources and the interaction with the soybean cyst nematode (Heterodera glycines Ichinohe, SCN), this research was undertaken with the following objectives - 1) to characterize the pathotype diversity of P. sojae causing Phytophthora root and stem rot on soybean in commercial fields in South Dakota; 2) to compare inoculation methods to evaluate for …

Evaluation Of Ecto-Mycorrhizae As A Determinant Of Chestnut Growth And Stress Response, Pabitra Aryal

Masters Theses

Although agriculture focuses on row crops throughout much of the Midwest, chestnut (Castanea spp.) appears to be an agroforestry crop well suited as a sustainable alternative to row crops in areas prone to erosion. As ectomycorrhizal (ECM) colonization is often crucial for tree establishment and production, I addressed the importance of ECM colonization on chestnut performance by assessing 1) natural ECM colonization in an established chestnut orchard and 2) the effect of experimental ECM inoculation on seedling establishment and drought response in a greenhouse. In the established orchard, I selected 50 Chinese-American hybrid chestnuts (C. mollisima x C. dentata …

Comparative Leaf Anatomy Of C3 And Cam Species In Oncidiinae (Maxillarieae, Orchidaceae), Samuel A. Eident

Masters Theses

The subtribe Oncidiinae is a diverse group of mostly epiphytic orchids within the tribe Maxillarieae, consisting of 55 genera and 1700 species. In this group, there have been many studies examining morphological and anatomical variation as well as metabolic pathways of carbon fixation, but most have not integrated morphological and anatomical variation with a physiological aspect of inquiry. The objective of my research was to establish a suite of anatomical characteristics that can be used to distinguish between C₃ and CAM species. Secondarily, I hoped to use that suite of characteristics in determining whether intermediate CAM species (those that …

Phylogenetics Of The Borage Family: Delimiting Boraginales And Assessing Closest Relatives, Kristen E. Hasenstab-Lehman

Aliso: A Journal of Systematic and Floristic Botany

The placement of Boraginales, and relationships within the family have remained elusive in modern, broad phylogenetic studies. In order to assess the phylogeny of Boraginales, and specifically to test the sister lineage of the order, a data matrix of the chloroplast markers rbcL, ndhF, and trnL-trnF was assembled from GenBank and de novo sequences (representing 132 new GenBank accessions). Phylogenies inferred using Maximum Likelihood and Bayesian frameworks resulted in identical topologies. Tests for alternative topologies were used to assess whether any of the candidates for sister (Solanales, Gentianales, Lamiales, or Vahlia) to Boraginales could …

Computational Fluid Dynamics Applied To Transport Systems In Trees, Katie E. Randolph, Paul J. Schulte Ph.D

McNair Poster Presentations

Our ecosystem is dependent upon the ability of photosynthetic plants to convert solar energy into a form of energy useable to biological organisms. Even so, much remains to become understood about how plants function. With such expansive bodies,how do trees cyclewaterand nutrients throughouttheir bodies?

Mitigating Risks Of Ochratoxin A Contamination In Oats, Bandana Dhungana

Electronic Theses and Dissertations

Ochratoxin A (OTA) is a toxic metabolite produced by several species of fungal genera Penicillium and Aspergillus. The major OTA producer in temperate regions (i.e. U.S., Canada, Europe) is Penicillium verrucosum. Oat (Avena sativa), like any other cereal grain, can be contaminated with OTA when storage conditions are favorable for fungal growth. The presence of OTA exceeding the European Union maximum limit of 3 ppb in processed food has been reported in some samples of oat-based breakfast cereals from the US. The use of oat genotypes with limited OTA accumulation would be an effective way to …

Impacts Of Crop Residue And Cover Crops On Soil Hydrological Properties, Soil Water Storage And Water Use Efficiency Of Soybean Crop, Kopila Subedi-Chalise

Electronic Theses and Dissertations

Cover crops and crop residue play a multifunctional role in improving soil hydrological properties, soil water storage and water use efficiency (WUE). This study was conducted to better understand the role of crop residue and cover crop on soil properties and soil water dynamics. The study was conducted at the USDA-ARS North Central Agricultural Research Laboratory, located in Brookings, South Dakota. Two residue removal treatments that include low residue removal (LRR) and high residue removal (HRR) were established in 2000 with randomized complete block design under no-till corn (Zea mays L.) and soybean (Glycine max L.) rotation. In 2005, cover …

Managing Phomopsis Stem Canker Of Sunflower Using Improved Diagnosis And Quantification Of The Causal Pathogens, Taylor Rae Olson

Electronic Theses and Dissertations

Phomopsis stem canker is a disease that severely affects sunflower (Helianthus annuus) in the United States. From 2001 to 2015, disease prevalence has increased from 1.5% to 61%, and two new causal agents, Diaporthe gulyae and Diaporthe stewartii, have been described along with Diaporthe helianthi, which was always regarded as the main causal pathogen of the disease. At this time, options to manage the disease are limited. Currently, no commercial sunflower hybrids have resistance to all three species of Diaporthe, and no fungicides are labeled for control of Phomopsis stem canker of sunflower in the United …

Perimeter Cropping As A Means Of Reducing Insect Injury And Increasing Crop Yield, Brett L. Owens

Electronic Theses and Dissertations

The squash vine borer, Melittia cucurbitae Harris, (Lepidoptera: Sesiidae) is a destructive insect known to injure a broad range of cucurbit crops. Many studies have focused on insecticide management of this insect in squash (Cucurbita) and pumpkin (Cucurbita pepo Linnaeus) production; however, little work has been documented on organic approaches to reduce or eliminate injury from this pest to these crops in the Midwest. This study used trap cropping and pollinator mixtures to test whether a reduction of squash vine borer could be achieved in a specific cultivar of pumpkins, Cucurbita pepo ‘Howden’. The study was …

Improvement Of Milling And Nutritional Quality Characteristics Of Oats Through Genomic Selection, Sudha Neupane Adhikari

Electronic Theses and Dissertations

Oats can lower cholesterol, reduce risks of type-2 diabetes, and help prevent heart diseases when consumed daily. Therefore, it is important to evaluate and select breeding lines with desirable milling and nutritional quality traits. Genomic selection, which uses genotyping data to predict the breeding value of an individual, is a promising method to increase genetic gain by selecting for quality traits earlier in the line development process. In this study, we collected phenotypic data for three nutritional traits (protein, β- glucan, and fat content) and five milling quality traits (percent plumps, percent thins, percent plump groat, groat percent and thousand …

Soil Response To Cropping Sequences And Grazing Under Integrated Crop-Livestock System, Hanxiao Feng

Electronic Theses and Dissertations

Integrated crop-livestock system (ICLS) is helpful in diversifying a farm for improving its long-term sustainability and economic benefits. In the United States, the ICLS has been increasing in recent years because of its economic and environmental benefits. However, the impacts of ICLS on soil quality is not well documented in North Dakota. The objective of our study is to assess the impacts of cropping sequences and cattle grazing on the selected soil properties in the crop diversity and livestock integration practice. This study site was established in 2010 at the Dickinson Research Extension Center, Dickinson, North Dakota. The study design …

Molecular Characterization Of Spot Blotch And Bacterial Leaf Streak Resistance In Bread Wheat, Girma Ayana

Electronic Theses and Dissertations

Spot blotch (SB), caused by Bipolaris sorokiniana (Sacc.) Shoem, and bacterial leaf streak (BLS), caused by Xanthomonas translucens pv. undulosa (Smith et al.), two important foliar diseases of wheat in the major production regions of the US and the world. Deployment of adequate host resistance against them depends on determining the resistance genes or quantitative trait loci (QTLs) responsible for the trait and identification of genetic markers linked to QTL that facilitate markers assisted breeding. We conducted two independent studies and characterized QTLs for BLS and SB resistance. In the first study, we constructed a genetic linkage map of 1,211 …

Effects Of Root Isoflavonoids And Hairy Root Transformation On The Soybean Rhizosphere Bacterial Community Structure, Laura White

Electronic Theses and Dissertations

Rhizodeposits play a key role in shaping rhizosphere microbial communities. In soybean, isoflavonoids are a key rhizodeposit component that aid in plant defense and enable symbiotic associations with rhizobia. However, it is uncertain if and how they influence rhizosphere microbial communities. Isoflavonoid biosynthesis was silenced via RNA interference of isoflavone synthase in soybean hairy root composite plants. Successive sonication was implemented to isolate soil fractions from 3 different rhizosphere zones at 1 and 3 weeks post planting. PCR amplicons from 16S rRNA gene variable regions V1- V3 and V3-V5 from these soil fractions were analyzed via denaturing gradient gel electrophoresis …

Differential Gene Expression In Two Nodule Zones Of Soybean, Sunita Pathak

Electronic Theses and Dissertations

Soybean, a leguminous plant and rhizobia establishes symbiotic relationships, forming root nodules. Nodule organogenesis starts with cortical cell division forming infection and parenchyma zones which houses N-fixing bacteria and block O2 for nitrogenase enzyme function, respectively. The mechanism by which root cortical cells give rise to two structurally and functionally different nodule tissues is not known. One approach to address this knowledge gap is to evaluate global gene expression patterns in these two tissue types during nodule development. Using INTACT method, we developed two promoters, ENOD2 (nodule parenchyma) and ENOD40 (infection zone) driven nuclear envelope biotin tagging constructs and isolated …

Regulation Of Arf16-2 By Microrna160 During Soybean Root Nodule Development, Spencer Schreier

Electronic Theses and Dissertations

Soybean is an excellent candidate for sustainable agriculture due to its production of nutritious, versatile beans and the ability to form symbiotic organs called root nodules that perform nitrogen fixation. As demand for both yield and sustainable agriculture continue to increase, root nodules offer an attractive alternative to expensive and environmentally harmful nitrogen fertilizers. Understanding root nodule formation may open genetic engineering avenues for optimizing nitrogen fixation performance and transferring the nodule-formation ability to other plants. A major determinant of nodule numbers and quality in soybean is microRNA 160 (miR160), which dictates developmental stage-specific auxin sensitivity by targeting repressor auxin …

Impacts Of Integrated Crop-Livestock System On Soil Surface Greenhouse Gas Fluxes At A Farm Scale In South Dakota, Brant Douville

Electronic Theses and Dissertations

Grazing and cover crops (CC) can impact soil nutrient cycling but may increase the greenhouse gas (GHG) emissions from soils. However, little is known about their impacts on soil properties and soil surface GHG emissions in an integrated crop-livestock system (ICLS) in South Dakota, USA. The present study was conducted at a farm scale at the Research Farm of South Dakota State University, Brookings, South Dakota, to assess the impact of cover crops and grazing on soil pH, electrical conductivity (EC), and bulk density (BD), and soil surface carbon dioxide (CO₂), methane (CH₄), and nitrous oxide …

Characterization Of Pyrenophora Tritici-Repentis In Wheat And Rye To Study Tan Spot Susceptibility And Insights Into Its Relationship With Stem Rust Resistance, Sidrat Abdullah

Electronic Theses and Dissertations

Tan spot, caused by the ascomycete fungus, Pyrenophora tritici-repentis (Ptr), is a major foliar fungal disease of wheat worldwide. To date, Ptr isolates have been grouped into eight races based on the production of three host selective effectors (toxins), Ptr ToxA, ToxB, and ToxC, which are associated with necrosis and chlorosis symptoms on wheat differential lines. In order to see the correlation between stem rust resistance and tan spot susceptibility in 1970’s, to know the pathogen virulence profile, and explore the sources of tan spot resistance, we recovered isolates from wheat and rye and evaluated wheat and rye lines with …

Silencing Seed Dormancy Genes To Mitigate Risk Of Transgene Flow To Weedy Rice, Alexander Wireko Kena

Electronic Theses and Dissertations

The flow of fitness-enhancing transgenes from genetically modified crops into wild/weed relatives may cause serious ecological and economic consequences. Seed dormancy (SD) is a key adaptive trait that distributes germination over time, resulting in weed persistence in agroecosystems. Thus, silencing major genes controlling SD would reduce the adaptive fitness of weeds. SD-enhancing genes cloned from weedy rice include SD7-1, SD7-2, SD12a, SD12b, and SD12c. The goal of this study was to develop a transgenic mitigation (TM) strategy using SD gene-silencing structures as mitigating factors to reduce the risk of transgene flow to wild/weed populations. TM vector constructs consisted of the …

Interactive Effects Of Cover Crops, Invertebrate Communities And Soil Health In Corn Production Systems, Claire Lacanne

Electronic Theses and Dissertations

The adoption of regenerative farming practices is gaining traction, but the costs and benefits are not often considered on a systems level. Encouraging biodiversity and soil health is the goal of many agricultural practices used in regenerative farming; regenerative systems employ practices which abide by the two main principles of increasing biodiversity and decreasing disturbance, with the goal of encouraging ecosystem functioning to minimize inputs and maximize the productivity of a farm. I examined the management of corn (Zea mays) fields across four states in the Upper Midwest region of the United States. Regenerative systems in this study …