Plant Pathology Commons^™

Effects Of Single And Double Infections Of Winter Wheat By Triticum Mosaic Virus And Wheat Streak Mosaic Virus On Yield Determinants, E. Byamukama, S. Tatineni, G. L. Hein, R. A. Graybosch, P. Stephen Baenziger, R. French, S. N. Wegulo

Department of Plant Pathology: Faculty Publications

Triticum mosaic virus (TriMV) is a recently discovered virus infecting wheat (Triticum aestivum) in the Great Plains region of the United States. It is transmitted by wheat curl mites (Aceria tosichella) which also transmit Wheat streak mosaic virus (WSMV) and Wheat mosaic virus. In a greenhouse study, winter wheat ‘Millennium’ (WSMV susceptible) and ‘Mace’ (WSMV resistant) were mechanically inoculated with TriMV, WSMV, TriMV+WSMV, or sterile water at the two-leaf growth stage. At 28 days after inoculation, final chlorophyll meter (soil plant analysis development [SPAD]) readings, area under the SPAD progress curve (AUSPC), the number of …

Host Pathogen Interactions: Is Arabidopsis Thaliana Remembered By Its Nemesis Pseudomonas Syringae?, Daniel Z. Kreiser

Lawrence University Honors Projects

Plants contain innate immune systems that deter pathogen infection. Pattern recognition receptors bind microbe-associated molecular patterns (MAMPs), triggering immunity. MAMPs are proteins exclusive to pathogens that are typically indispensable for their survival. For this reason, MAMPs cannot be mutated or removed without causing pathogen death. However, this does not necessitate constitutive expression of MAMPs. In this study, the MAMP response of Arabidopsis thaliana was utilized to determine differential detection of MAMPs expressed by Pseudomonas syringe pv. tomato DC3000 when pretreated with A. thaliana. Results demonstrated that more MAMPs are detected when P. syringae had previously encountered A. thaliana, …

Genotypic And Phenotypic Diversity Of Pyricularia Oryzae In The Contemporary Rice Blast Pathogen Population In Arkansas, Lu Zhai

Graduate Theses and Dissertations

Rice blast, caused by Pyricularia oryzae (teleomorph: Magnaporthe grisea), is one of the most economically important diseases of rice worldwide, including Arkansas. Rice blast has been severe the past few years on conventional cultivars and, more recently, has been observed on hybrid rice cultivars. The first objective of the current research was to examine the genotypic and phenotypic variation in the P. oryzae population in Arkansas during the 2009, 2010, and 2011 growing seasons and compare isolates from conventional cultivars with those from and hybrids. A total of 904 isolates were recovered from symptomatic rice cultivars in Arkansas and …

Principles Of Carbon Catabolite Repression In The Rice Blast Fungus: Tps1, Nmr1-3, And A Mate–Family Pump Regulate Glucose Metabolism During Infection, Jessie Fernandez, Janet D. Wright, David E. Hartline, Cristian Fernando Quispe, Nandakumar Madayiputhiya, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

Understanding the genetic pathways that regulate how pathogenic fungi respond to their environment is paramount to developing effective mitigation strategies against disease. Carbon catabolite repression (CCR) is a global regulatory mechanism found in a wide range of microbial organisms that ensures the preferential utilization of glucose over less favourable carbon sources, but little is known about the components of CCR in filamentous fungi. Here we report three new mediators of CCR in the devastating rice blast fungus Magnaporthe oryzae: the sugar sensor Tps1, the Nmr1-3 inhibitor proteins, and the multidrug and toxin extrusion (MATE)-family pump, Mdt1. Using simple plate …

The Foliar Nematode Aphelenchoides Fragariae: Studies On Facultative Feeding And Desiccation Tolerance, Zhen Fu

All Dissertations

The foliar nematode Aphelenchoides fragariae is an economically important and frequent pest of ornamental crops. In nurseries and landscapes in the United States, foliar nematodes can be a serious problem affecting hostas (Hosta spp.), a common perennial ornamental plant that thrives in shady environments. Fundamental research on the biology and ecology of this nematode provides the basis for development of sound management strategies. The general objective of this dissertation was to study two behaviors that make foliar nematodes very successful as plant pests: desiccation tolerance and alternative feeding on fungi (or facultative feeding on the plant). To study the molecular …

The Effect Of Phosphite On Mycorrhiza Formation In American Chestnut (Castanea Dentata), Matthew T. Perkins

Honors Theses

One of the primary hindrances to Castanea dentata restoration in the Southeast is the root rot disease caused by the fungus-like microorganism Phytophthora cinnamomi. Root rot can be combated by the application of mono- and di-potassium salts of phosphorous acid, which are marketed as phosphite fungicides. Despite its value in preventing infection by P. cinnamomi it is also thought that phosphite may impede root colonization by beneficial, ectomycorrhizal fungi. I hypothesized that plants given a routine application of phosphite will display fewer mycorrhizas in the root tips than those plants that were not treated with potassium phosphite. Therefore I attempted …

Early Season Population Dynamics And Residual Insecticide Effects On Bird Cherry-Oat Aphid, Rhopalosiphum Padi In Arkansas Winter Wheat, Beven Mcwilliams

Graduate Theses and Dissertations

Bird cherry-oat aphid is a common pest of Arkansas winter wheat. This aphid vectors barley yellow dwarf virus which may cause extensive crop damage and yield loss when wheat is infested by virulent aphids in the fall. Some suggest this damage may be avoided using insecticide seed treatments if growers are unable to delay planting, as is recommended. Field population dynamics of bird cherry-oat aphid during fall 2009 and 2010 was assessed through random sampling of whole plants and pan trapping methods to evaluate aphid immigration. The field plots were divided into four subplots treated with a systemic insecticide seed …

Biology, Histopathology, And Improvements In Axenic Culture Of Labyrinthula Terrestris, Causal Agent Of Rapid Blight Of Cool-Season Turfgrasses, Kirthi Kiran Yadagiri

All Dissertations

Rapid blight is a disease of cool-season turfgrasses caused by Labyrinthula terrestris. Disease symptoms include water-soaked lesions, yellowing and browning of foliage, and coalescing patches of dead turf. L. terrestris belongs to a group of marine microorganisms in the kingdom Chromista (also known as Stramenopila). Morphological characteristics of Labyrinthula spp. include spindle-shaped vegetative cells that move in an ectoplasmic network. The biology and pathology of L. terrestris is not clearly understood; therefore, the ultrastructure, life cycle, and histopathology of L. terrestris were investigated. In addition, improvements in axenic culture and long-term storage methods were made to better culture L. terrestris. …

Fungicide, Herbicide, And Genotype Effects On Charcoal Rot And Phomopsis Seed Decay In Soybean, Cory Cross

Student Theses and Dissertations

Yield limiting diseases such as charcoal rot and Phomopsis seed decay have a significant impact on the economic potential for soybeans because there are few methods for management of these diseases. The objectives of this study were to evaluate application of the herbicide lactofen, the fungicide azoxystrobin, and soybean genotype effects on charcoal rot and Phomopsis seed decay. Bacterial blight and pod and stem blight also developed during the course of this study, and the effects of treatments on these diseases were evaluated. Application of lactofen and azoxystrobin had no significant impact on severity of charcoal rot, percent of harvested …

Strawberry Growth, Yield, Fruit Nutrition, And Control Of Verticillium Wilt With Pre-Plant Soil Fumigants, Ozone, And Biological Control, Justin J. Scurich

Master's Theses

Verticillium wilt is a widespread soilborne disease of strawberry historically controlled by soil fumigation with methyl bromide (MB). MB was banned by the United Nations in 1995 and will be completely phased out by 2015. Research has concentrated on alternative methods of disease control without finding a single alternative able to replace MB in widespread disease control and yield increase. For the current study, strawberries were greenhouse grown in container pots filled with soil from both infested and non-infested areas of a commercial strawberry field in Watsonville, CA. Treatments included pre-plant soil fumigation with commercially available formulations of methyl bromide, …

Evidence Of Reduced Arbuscular Mycorrhizal Fungal Colonization In Multiple Lines Of Bt Maize, Tanya E. Cheeke, Todd N. Rosenstiel, Mitchell B. Cruzan

Biology Faculty Publications and Presentations

Premise of the Study: Insect-resistant Bacillus thuringiensis (Bt) maize is widely cultivated, yet few studies have examined the interaction of symbiotic arbuscular mycorrhizal fungi (AMF) with different lines of Bt maize. As obligate symbionts, AMF may be sensitive to genetic changes within a plant host. Previous evaluations of the impact of Bt crops on AMF have been inconsistent, and because most studies were conducted under disparate experimental conditions, the results are difficult to compare. Methods: We evaluate AMF colonization in nine Bt maize lines, differing in number and type of engineered trait, and five corresponding near-isogenic parental (P) base hybrids …

Proceedings Of The 39th Annual Meeting, Southern Soybean Disease Workers (March 7-8, 2012, Pensacola Beach, Florida), Tom Allen, Boyd Padgett, Danise Beadle, Stephen R. Koenning

Southern Soybean Disease Workers: Conference Proceedings

Contents

Symposium: Soybean Nematodes: Their Status, Impact and Management

The Current Status of Nematodes of Soybean in Louisiana and Arkansas. Charles Overstreet, Edward C McGawley, Melea Martin, and Terry Kirkpatrick

A Molecular Analysis of Resistance of Soybean to the Soybean Cyst Nematode. Vincent Klink

Racism in Nematology. Terry Niblack

SCN-resistant Soybeans, HG types, Yield, and SCN Reproduction: How It All Comes Together in the Field in Iowa. Gregory Tylka

Soybean Lines Evaluated for Resistance to Reniform Nematode. Sally Stetina

Graduate student presentations (Boyd Padgett, moderator)

Fungicide Resistance in Cercospora kikuchii, a Major Pathogen of Louisiana Soybean. Trey Price

Variation …

Bean Leaf Beetle (Coleoptera: Chrysomelidae) And Bean Pod Mottle Virus In Soybean: Biology, Ecology, And Management, Buyung A. R. Hadi, Jeffrey D. Bradshaw, Marlin E. Rice, John J. Hill

Department of Entomology: Faculty Publications

Bean leaf beetle, Cerotoma trifurcata (Förster), is a pest of soybean found in many production areas in the United States. The bean leaf beetle larvae feed on soybean root nodules, whereas the adults feed on the above ground parts of soybean such as cotyledon, leaves, and pods. Bean leaf beetle is also a very efficient vector of Bean pod mottle virus, a widespread virus of soybean in the south and southeastern United States with recent expansion into the north central region of the country. This article summarizes bean leaf beetle biology, ecology, and its impact on soybean production in the …

Plant Wounding And Ophiostoma Mitovirus 3a (Omv3a) Influence Infection Of Creeping Bentgrass By Sclerotinia Homoeocarpa, Angela M. Orshinsky, Michael J. Boehm, Greg J. Boland

Department of Plant Pathology: Faculty Publications

Colonization and lesion development by virulent, asymptomatic and hypovirulent isolates of Sclerotinia homoeocarpa on nonwounded (NW) and wounded (W) leaves of creeping bentgrass were characterized. Hypovirulent and asymptomatic isolates contain the fungal virus, Ophiostoma mitovirus 3a, and virulent isolates are virus-free. On NW leaves, all isolates infected leaves with appressoria along cell walls and through stomata by 48 hours post-inoculation (hpi). Inter- and intracellular hyphae formed on heavily colonized, NW leaves at 96 hpi. Wound-inoculated grass had a colonization front characterized by inter- and intracellular hyphal colonization within nonsymptomatic tissues at 8 hpi by direct infection of the wound …

A Co-Opted Dead-Box Rna Helicase Enhances Tombusvirus Plus-Strand Synthesis, Nikolay Kovalev, Judit Pogany, Peter D. Nagy

Plant Pathology Faculty Publications

Replication of plus-strand RNA viruses depends on recruited host factors that aid several critical steps during replication. In this paper, we show that an essential translation factor, Ded1p DEAD-box RNA helicase of yeast, directly affects replication of Tomato bushy stunt virus (TBSV). To separate the role of Ded1p in viral protein translation from its putative replication function, we utilized a cell-free TBSV replication assay and recombinant Ded1p. The in vitro data show that Ded1p plays a role in enhancing plus-strand synthesis by the viral replicase. We also find that Ded1p is a component of the tombusvirus replicase complex and Ded1p …

The Tpr Domain In The Host Cyp40-Like Cyclophilin Binds To The Viral Replication Protein And Inhibits The Assembly Of The Tombusviral Replicase, Jing-Yi Lin, Venugopal Mendu, Judit Pogany, Jun Qin, Peter D. Nagy

Plant Pathology Faculty Publications

Replication of plus-stranded RNA viruses is greatly affected by numerous host-coded proteins acting either as susceptibility or resistance factors. Previous genome-wide screens and global proteomics approaches with Tomato bushy stunt tombusvirus (TBSV) in a yeast model host revealed the involvement of cyclophilins, which are a large family of host prolyl isomerases, in TBSV replication. In this paper, we identified those members of the large cyclophilin family that interacted with the viral replication proteins and inhibited TBSV replication. Further characterization of the most effective cyclophilin, the Cyp40-like Cpr7p, revealed that it strongly inhibits many steps during TBSV replication in a cell-free …

Vitamin Deficiencies In Humans: Can Plant Science Help?, Teresa B. Fitzpatrick, Gilles J. C. Basset, Patrick Borel, Fernando Carrari, Dean Dellapenna, Paul D. Fraser, Hanjo Hellmann, Sonia Osorio, Christophe Rothan, Victoriano Valpuesta, Catherine Caris-Veyrat, Alisdair R. Fernie

Center for Plant Science Innovation: Faculty Publications

The term vitamin describes a small group of organic compounds that are absolutely required in the human diet. Although for the most part, dependency criteria are met in developed countries through balanced diets, this is not the case for the five billion people in developing countries who depend predominantly on a single staple crop for survival. Thus, providing a more balanced vitamin intake from high-quality food remains one of the grandest challenges for global human nutrition in the coming decade(s). Here, we describe the known importance of vitamins in human health and current knowledge on their metabolism in plants. Deficits …

Soybean Disease Profiles I: Foliar Diseases, Loren J. Giesler, Robert M. Harveson, Tamra A. Jackson-Ziems, Kevin A. Korus, Bo Liu, Stephen N. Wegulo

Department of Plant Pathology: Faculty Publications

Extension Circular 1093 (EC1903).

Disease photographs and descriptions of Bacterial Blight, Bacterial Pustule, Brown Spot, Cercospora Leaf Blight and Purple Seed Stain, Downy Mildew, Frogeye Leaf Spot, Soybean Rust, Powdery Mildew, and Bean Pod mottle and Soybean Mosaic.

Effects Of Foliar Fungicides And Application Timing On Field Corn In Nebraska, 2011, C. M. Schleicher, T. A. Jackson

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 62-54, rating of “good” (6 out of 9) for gray leaf spot (GLS) and “excellent” (2 out of 9) for common rust (CR), was planted on 2 May in 30 in. rows with a target population of 32,000 plants/A. The trial area was disked with soybean as the previous year’s crop. On 9 May before plant emergence, a herbicide program of Roundup (1 pt/A), Verdict (16 fl oz/A) and Atrazine (1 lb/A) was applied to …

Evaluation Of Application Timing Of Foliar Fungicides On Efficacy Of Field Corn At Ardc In Eastern Nebraska, 2011, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln Agricultural Research and Development Center near Mead, NE. Pioneer corn hybrid P0832XR was planted on 10 May in 30 in. rows with a target population of 30,000 plants/A. The trial area was disked in the early spring with corn as the previous year’s crop. A herbicide program of Lexar (3 pts/A) + Roundup PowerMax (22 fl oz/A) +AMS was applied to the trial. Nine treatments and a non-treated control were replicated five times in a randomized complete block design. Each plot was four rows (10 ft) wide …

Evaluation Of Application Timing Of Foliar Fungicides On Efficacy Of Field Corn In Central Nebraska, 2011, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 62-54, rating of “good” (6 out of 9) for gray leaf spot (GLS) and “excellent” (2 out of 9) for common rust (CR), was planted on 3 May in 30 in. rows with a target population of 32,000 plants/A. The trial area was disked with a crop history of seven years of continuous corn. On 9 May before plant emergence, a herbicide program of Roundup (1 pt/A), Verdict (16 fl oz/A) and Atrazine (1 lb/A) …

Effectiveness Of Foliar Fungicides By Timing On Hybrid Corn, Alison E. Robertson, John M. Shriver, David Rueber

Northern Research and Demonstration Farm

Fungicide use on hybrid corn has increased considerably in the past several growing seasons, primarily due to reports of increased yields, even in the absence of disease and higher corn prices. A number of fungicides are registered for use on corn. The objectives of this project were to 1) assess the effect of timing of application of fungicides on standability, 2) evaluate the yield response of hybrid corn to foliar fungicide application, and 3) discern differences, if any, between fungicide products.

Efficacy Evaluation Of Foliar Fungicides In Field Corn With Low Disease Pressure In Central Nebraska, 2011, C. M. Schleicher, T. A. Jackson

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 62-54, rating of “good” (6 out of 9) for gray leaf spot (GLS) and “excellent” (2 out of 9) for common rust (CR), was planted on 3 May in 30 in. rows with a target population of 32,000 plants/A. The trial area was disked with a crop history of seven years of continuous corn. On 9 May before plant emergence, a herbicide program of Roundup (1 pt/A), Verdict (16 fl oz/A) and Atrazine (1 lb/A) was …

Morphogenetic And Developmental Functions Of The Aspergillus Nidulans Homologues Of The Yeast Bud Site Selection Proteins Bud4 And Axl2, Haoyu Si, William R. Rittenour, Kaimei Xu, Mark Nicksarlian, Ana M. Calvo, Steven D. Harris

Department of Plant Pathology: Faculty Publications

The yeast bud site selection system represents a paradigm for understanding how fungal cells regulate the formation of a polarity axis. In Saccharomyces cerevisiae, Bud4 and Axl2 are components of the axial bud site marker. To address the possibility that these proteins regulate cellular morphogenesis in filamentous fungi, we have characterized homologues of Bud4 and Axl2 in Aspergillus nidulans. Our results show that Bud4 is involved in septum formation in both hyphae and developing conidiophores. Whereas Axl2 appears to have no obvious role in hyphal growth, it is required for the regulation of phialide morphogenesis during conidiation. In …

Efficacy Evaluation Of Foliar Fungicide Application Timing In Field Corn In Central Nebraska, 2011, C. M. Schleicher, T. A. Jackson

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 62-54, rating of “good” (6 out of 9) for gray leaf spot (GLS) and “excellent” (2 out of 9) for common rust (CR), was planted on 3 May in 30 in. rows with a target population of 32,000 plants/A. The trial area was disked with a crop history of seven years of continuous corn. On 9 May before plant emergence, a herbicide program of Roundup (1 pt/A), Verdict (16 fl oz/A) and Atrazine (1 lb/A) …

Sunflower Disease Profiles I: Foliar Diseases, Robert M. Harveson, Loren J. Giesler, Tamra A. Jackson, Bo Liu, Stephen N. Wegulo, Kevin A. Korus

Department of Plant Pathology: Faculty Publications

Extension Circular 1900 (EC1900).

Photographs and disease descriptions of Viruses, Apical Chlorosis, Downy Mildew, Rust, Alternia Leaf Spot, and Bacterial Leaf Spot.

Critical Roles Of Rna-Binding Proteins In Mirna Biogenesis In Arabidopsis, Guodong Ren, Bin Yu

Center for Plant Science Innovation: Faculty Publications

MicroRNAs (miRNAs) are key regulators of gene expression and play critical roles in modulating metabolism, development and physiology in animals and plants. miRNA levels are transcriptionally and post-transcriptionally controlled for their proper function. Recent studies have shown that RNA-binding proteins play important roles in producing miRNAs by affecting the accurate and/or efficient processing of precursors of miRNAs. Many of these RNA-binding proteins also have roles in general RNA metabolism, indicating potential connections between miRNA biogenesis and other RNA metabolism. Here, we focus on the function of several RNA-binding proteins in miRNA biogenesis in Arabidopsis.

Post-Transcriptional Control Of Mirna Abundance In Arabidopsis, Guodong Ren, Bin Yu

Center for Plant Science Innovation: Faculty Publications

MicroRNAs (miRNAs) are a class of small non-coding RNAs (small RNAs) that are 20–24nt in length and predominantly repress gene expression at post-transcriptional levels. They regulate many biological processes including development, metabolism and physiology. Numerous studies have revealed that the steady-state levels of miRNA are under sophisticated control to ensure their proper function. In this review, we summarize recent advances on regulation of miRNA processing and stability in plants.

Uridylation Of Mirnas By Hen1 Suppressor1 In Arabidopsis, Guodong Ren, Xuemei Chen, Bin Yu

Center for Plant Science Innovation: Faculty Publications

HEN1-mediated 2′-O-methylation has been shown to be a key mechanism to protect plant microRNAs (miRNAs) and small interfering RNAs (siRNAs) as well as animal piwi-interacting RNAs (piRNAs) from degradation and 3′ terminal uridylation [1–8]. However, enzymes uridylating unmethylated miRNAs, siRNAs, or piRNAs in hen1 are unknown. In this study, a genetic screen identified a second-site mutation hen1 suppressor1-2 (heso1-2) that partially suppresses the morphological phenotypes of the hypomorphic hen1-2 allele and the null hen1-1 allele in Arabidopsis. HESO1 encodes a terminal nucleotidyl transferase that prefers to add untemplated uridine to the 3′ end of RNA, which is …

The Dna- And Rna-Binding Protein Factor Of Dna Methylation 1 Requires Xh Domain-Mediated Complex Formation For Its Function In Rna-Directed Dna Methylation, Meng Xie, Guodong Ren, Chi Zhang, Bin Yu

Center for Plant Science Innovation: Faculty Publications

Studies have identified a sub-group of SGS3-LIKE proteins including FDM1–5 and IDN2 as key components of RNA-directed DNA methylation pathway (RdDM). Although FDM1 and IDN2 bind RNAs with 5' overhangs, their functions in the RdDM pathway remain to be examined. Here we show that FDM1 interacts with itself and with IDN2. Gel filtration suggests that FDM1 may exist as a homodimer in a heterotetramer complex in vivo. The XH domain of FDM1 mediates the FDM1–FDM1 and FDM1–IDN2 interactions. Deletion of the XH domain disrupts FDM1 complex formation and results in loss-of-function of FDM1. These results demonstrate that XH domainmediated …