Digital Commons Network^™

Effects Of Crop Injury On Disease Development, Tamra A. Jackson, Loren J. Giesler, Robert M. Harveson

Department of Plant Pathology: Faculty Publications

The effect of damage caused by blowing soil and leaf contact with high speed winds and hail will all create a similar level of wounding that is often sufficient for pathogens that require wounds to enter (infect) plants. As we look at the level of disease and crop damage we can identify several examples in the corn and soybean disease systems when this can be a factor that could lead to significant disease development and possibly trigger a disease management action.

Hail and wind damage can result in an open canopy which can affect the microclimate and impact disease development. …

What's New In Plant Pathology: Resistance: Mystery And Misunderstandings, Amy D. Timmerman, Loren J. Giesler, Robert M. Harveson, Tamra Jackson-Ziems, Stephen N. Wegulo

Department of Plant Pathology: Faculty Publications

One of the most common management recommendations for plant diseases is the use of resistant or tolerant varieties/hybrids in your production system. However, there is common confusion on the definition and differentiation of susceptible, tolerant, and resistant varieties/hybrids from a plant pathology viewpoint. A susceptible variety/hybrid allows the pathogen to reproduce and causes significant disease development and in turn compromises the productivity of the plant (i.e., yield). A tolerant variety/hybrid allows the pathogen to reproduce and cause disease at the same or at a slightly reduced rate as a susceptible variety/cultivar; however, there is no noticeable reduction in the plant’s …

Determining The Virulence Of Corn Pathogen Fusarium Verticillioides Utilizing Deletion Mutants Lacking Genes Fv_00027 Or Fv_Nps6, Abigail Zieman

Honors Program Theses

Fusarium verticillioides is an important fungal pathogen of com. Many pathogens have virulent genes which are genes that increase infectivity of the pathogen. After a bioinformatics study, it was determined that genes Fv _ 00027 and Fv _ NPS6 are potential virulent genes in F. verticillioides. To determine if either gene ·contributes to the virulence of the fungus, deletion mutants of F. verticillioides were created lacking either Fv _ 00027 or Fv _ NPS6 genes. These deletion mutants were utilized in an optimized com assay to determine the effect of infectivity on com. To test these deletion mutants, com seeds …

Synergistic Roles Of Eukaryotic Translation Elongation Factors 1bγ And 1a In Stimulation Of Tombusvirus Minus-Strand Synthesis, Zsuzsanna Sasvari, Lara Izotova, Terri Goss Kinzy, Peter D. Nagy

Plant Pathology Faculty Publications

Host factors are recruited into viral replicase complexes to aid replication of plus-strand RNA viruses. In this paper, we show that deletion of eukaryotic translation elongation factor 1Bgamma (eEF1Bγ) reduces Tomato bushy stunt virus (TBSV) replication in yeast host. Also, knock down of eEF1Bγ level in plant host decreases TBSV accumulation. eEF1Bγ binds to the viral RNA and is one of the resident host proteins in the tombusvirus replicase complex. Additional in vitro assays with whole cell extracts prepared from yeast strains lacking eEF1Bγ demonstrated its role in minus-strand synthesis by opening of the structured 3' end of the viral …

Bacterial Interactions Of Inoculated Price's Potato Bean (Apios Priceana): A Biological Study, Rhonda Walker

Masters Theses & Specialist Projects

Apios priceana is a native endangered species plant found in the Southeast United States. It is characterized as a leguminous species that bears wisteria like clusters with pea like flowers, a large tuberous root and four to six inch long seed pods. It is believed the Native Americans and early European settlers relied on this species as a source of protein and utilized the seeds for cultivation of the tuberous “potato” which formed. Apios priceana contains an average of 13% fiber, 6.9% protein, 71% carbohydrate and 9 of the 11 essential amino acids needed in human diets (Walter et al.,1986). …

Gene Expression And Physiological Analyses To Study Metabolic Shifts In Medicago Truncatula Subjected To Biotic Stresses, Michelle Ryan Martin

Graduate Theses and Dissertations

Plants are frequently under attack from pests and deploy various defense mechanisms to fight off predators. Many plant defenses are induced following herbivory or pathogen infection. An investment in defense could potentially lead to a diversion of metabolic resources away from primary metabolism, including reduction in plant commitment to photosynthesis. In this thesis, changes in expression levels of representative genes for primary and secondary metabolism were studied using real-time polymerase chain reaction (PCR) in Medicago truncatula Gaertner subjected to beet armyworm (Spodoptera exigua H¨¹bner) damage or Phoma medicaginis Malbr. & Roum. infection. Photosynthetic yield was also measured using chlorophyll fluorescence …

Ecological Disinfestation: Physical And Biological Characterization Of Filtration Substrates For Removing Zoospores Of Phytophthora Nicotianae From Water, Elizabeth Nyberg

All Theses

Although recycling irrigation water is beneficial to the nursery industry as it serves to decrease potable water usage and reduces the release of excess agrichemicals into the environment, it also poses the risk of becoming the source for and means of dispersing water-borne plant pathogens. Plant pathogens of major concern in irrigation water are species of Phytophthora. These pathogens are a significant threat because they can attack a vast number of plants, many of which are ornamental crops grown in nurseries, by releasing motile zoospores directly into irrigation water. Several treatment methods are available to remove plant pathogens from irrigation …

Fungal Virulence And Development Is Regulated By Alternative Pre-Mrna 3′End Processing In Magnaporthe Oryzae, Marina Franceschetti, Emilio Bueno, Richard A. Wilson, Sara L. Tucker, Concepción Gómez-Mena, Grant Calder, Ane Sesma

Fungal Molecular Plant-Microbe Interactions

RNA-binding proteins play a central role in post-transcriptional mechanisms that control gene expression. Identification of novel RNA-binding proteins in fungi is essential to unravel post-transcriptional networks and cellular processes that confer identity to the fungal kingdom. Here, we carried out the functional characterisation of the filamentous fungus-specific RNAbinding protein RBP35 required for full virulence and development in the rice blast fungus. RBP35 contains an N-terminal RNA recognition motif (RRM) and six Arg-Gly-Gly tripeptide repeats. Immunoblots identified two RBP35 protein isoforms that show a steady-state nuclear localisation and bind RNA in vitro. RBP35 coimmunoprecipitates in vivo with Cleavage Factor I (CFI) …

Analysis Of Turnip Crinkle Virus Effects On The Innate And Adaptive Immunity In Arabidopsis Thaliana, Teresa J. Donze

School of Biological Sciences: Dissertations, Theses, and Student Research

The ability to understand the interactions between plants and the variety of pathogens they encounter on a daily basis is an important area of research. In the following work presented in this dissertation, I sought to better understand the mechanisms that Turnip crinkle virus (TCV) employs to elude the defense responses of the host plant Arabidopsis thaliana. It was previously determined that TCV coat protein (CP) interacts with a transcription factor, TIP, within the about 10 amino acid region near the N-terminus of the CP called the R-domain. When this interaction was disrupted by making single amino acid substitutions …

A Plant Virus Evolved By Acquiring Multiple Nonconserved Genes To Extend Its Host Range, Satyanarayana Tatineni, Cecile J. Robertson, Stephen M. Garnsey, William O. Dawson

Department of Plant Pathology: Faculty Publications

Viruses have evolved as combinations of genes whose products interact with cellular components to produce progeny virus throughout the plants. Some viral genes, particularly those that are involved in replication and assembly, tend to be relatively conserved, whereas other genes that have evolved for interactions with the specific host for movement and to counter host–defense systems tend to be less conserved. Closteroviridae encode 1–5 nonconserved ORFs. Citrus tristeza virus (CTV), a Closterovirus, possesses nonconserved p33, p18, and p13 genes that are expendable for systemic infection of the two laboratory hosts, Citrus macrophylla and Mexican lime. In this study, we …

Widespread Horizontal Gene Transfer From Circular Single-Stranded Dna Viruses To Eukaryotic Genomes, Huiquan Liu, Yanping Fu, Bo Li, Xiao Yu, Jiatao Xie, Jiasen Cheng, Said A. Ghabrial, Guoqing Li, Xianhong Yi, Daohong Jiang

Plant Pathology Faculty Publications

BACKGROUND: In addition to vertical transmission, organisms can also acquire genes from other distantly related species or from their extra-chromosomal elements (plasmids and viruses) via horizontal gene transfer (HGT). It has been suggested that phages represent substantial forces in prokaryotic evolution. In eukaryotes, retroviruses, which can integrate into host genome as an obligate step in their replication strategy, comprise approximately 8% of the human genome. Unlike retroviruses, few members of other virus families are known to transfer genes to host genomes.

RESULTS: Here we performed a systematic search for sequences related to circular single-stranded DNA (ssDNA) viruses in publicly available …

Rna-Mediated Silencing In Algae: Biological Roles And Tools For Analysis Of Gene Function, Heriberto Cerutti, Xinrong Ma, Joseph Msanne, Timothy Repas

Center for Plant Science Innovation: Faculty Publications

Algae are a large group of aquatic, typically photosynthetic, eukaryotes that include species from very diverse phylogenetic lineages, from those similar to land plants to those related to protist parasites. The recent sequencing of several algal genomes has provided insights into the great complexity of these organisms. Genomic information has also emphasized our lack of knowledge of the functions of many predicted genes, as well as the gene regulatory mechanisms in algae. Core components of the machinery for RNA-mediated silencing show widespread distribution among algal lineages, but they also seem to have been lost entirely from several species with relatively …

Muts Homolog1 Is A Nucleoid Protein That Alters Mitochondrial And Plastid Properties And Plant Response To High Light, Ying-Zhi Xu, Maria P. Arrieta-Montiel, Kamaldeep S. Virdi, Wilson B. M. De Paula, Joshua R. Widhalm, Gilles J. Basset, Jaime I. Davila, Thomas Elthon, Christian G. Elowsky, Shirley J. Sato, Thomas E. Clemente, Sally Ann Mackenzie

Center for Plant Science Innovation: Faculty Publications

Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve both mitochondrial- and plastid-localized steps. However, at an environmental response level, it is not clear how the two organelles intersect in programmed cellular responses. Here, we provide evidence, using genetic perturbation of the MutS Homolog1 (MSH1) nuclear gene in five plant species, that MSH1 functions within the mitochondrion and plastid to influence organellar genome behavior and plant growth patterns. The mitochondrial form of the protein participates in DNA recombination …

Gata-Family Transcription Factors In Magnaporthe Oryzae, Cristian F. Quispe

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The filamentous fungus, Magnaporthe oryzae, responsible for blast rice disease, destroys around 10-30% of the rice crop annually. Infection begins when the specialized infection structure, the appressorium, generates enormous internal turgor pressure through the accumulation of glycerol. This turgor acts on a penetration peg emerging at the base of the cell, causing it to breach the leaf surface allowing its infection.

The enzyme trehalose-6- phosphate synthase (Tps1) is a central regulator of the transition from appressorium development to infectious hyphal growth. In the first chapter we show that initiation of rice blast disease requires a regulatory mechanism involving an …

Population Genetics Of Cell-To-Cell Movement Of Wheat Streak Mosaic Virus, Melissa Sue Bartels

School of Biological Sciences: Dissertations, Theses, and Student Research

Previous workers in the lab created an infectious clone of Wheat Streak Mosaic Virus (WSMV) designated S1RN. An additional infectious clone with a GUS insert was also created to permit easy observation of virus movement (Gus1RN). A single point mutation made within the HC-Pro region created a mutant of WSMV designated PS81 that was unable to cause a systemic viral infection, although it could infect small clusters of cells on inoculated leaves. A similar mutation was made in the Gus1RN clone and it was designated Gus46. These particular mutants were capable of reverting back to wild type WSMV at high …

Identification Of Alternaria Alternata As A Causal Agent For Leaf Blight In Syringa Species, Margaret T. Mmbaga, Ainong Shi, Mee-Sook Kim

Agricultural and Environmental Sciences Faculty Research

While many isolates of Alternaria alternata are common saprophytes on trees and shrubs, this study clearly demonstrated that A. alternata is a primary pathogen in lilac (Syringa sp.), causing a leaf-blight that affects different Syringa species. Isolates of Alternaria sp. were collected from leaf blight samples of lilacs in the field. The internal transcribed spacer (ITS) region and morphological characterization were used to identify lilac blight pathogen. Based on 100% ITS nucleotide sequence identities to the Alternaria genus in the GenBank and morphological features, these isolates were identified as A. alternata. Disease symptoms were reproduced in lilac plants inoculated with …

Biology, Systematics, Phylogenetic Analysis And Dna Character-Based Species Diagnosis Of The False Root-Knot Nematode Nacobbus Aberrans (Thorne, 1935) Thorne & Allen 1944 (Nemata: Pratylenchidae), Angel Ramirez-Suarez

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The False Root-Knot nematode Nacobbus aberrans is a plant parasitic nematode that causes yield losses in several crops and plant protection agencies have established regulations to prevent infestations from spreading to new agricultural areas. The taxonomic status of the nematode has been the subject of controversy due to wide degree of variation exhibited by the species. This variability has led to the suggestion that N. aberrans is actually a species complex rather than a single species. In order to test this hypothesis, we compared twelve N. aberrans populations, which include isolates from western Nebraska, two distinct regions of Mexico and …

An Effective Virus-Based Gene Silencing Method For Functional Genomics Studies In Common Bean, Claudia Díaz-Camino, Padmanaban Annamalai, Federico Sanchez, Aardra Kachroo, Said A. Ghabrial

Plant Pathology Faculty Publications

BACKGROUND: Common bean (Phaseolus vulgaris L.) is a crop of economic and nutritious importance in many parts of the world. The lack of genomic resources have impeded the advancement of common bean genomics and thereby crop improvement. Although concerted efforts from the "Phaseomics" consortium have resulted in the development of several genomic resources, functional studies have continued to lag due to the recalcitrance of this crop for genetic transformation.

RESULTS: Here we describe the use of a bean pod mottle virus (BPMV)-based vector for silencing of endogenous genes in common bean as well as for protein expression. This BPMV-based vector …

Pathogen Induced Hypersensitive Response And Systemic Acquired Resistance In The Moss Amblystegium Serpens, Collin Elliot Bowman

Undergraduate Honors Thesis Collection

The moss Amblystegium serpens and the pathogenic fungus Pythium irregulare were used to study plant-pathogen interactions in a non-vascular plant. The major findings in this report include that P. irregulare does infect A. serpens but entire moss death was not noted, 25°C is the optimum temperature for P. irregulare appressoria formation, most appressoria were found on A. serpens leaves, and the SAR response within A. serpens seems to be reducing the number of P. irregulare penetrated moss cells. Future research on the pathogen defense mechanisms of A. serpens is important and promising. When we elucidate these complex chemical processes in …

Proceedings Of The 38th Annual Meeting, Southern Soybean Disease Workers (March 9-10, 2011, Pensacola Beach, Florida), Boyd Padgett, Tom Allen, Jason Bond, Cliff Coker, Stephen R. Koenning

Southern Soybean Disease Workers: Conference Proceedings

Contents

Southern United States Soybean Disease Loss Estimates for 2010. Compiled by SR Koenning

Poster presentation

Soybean Varieties and Breeding Lines Shown With Resistance to Reniform Nematode in Greenhouse Tests, 1998-2010 R. T. Robbins, and L. E. Jackson

Oral presentations

Frogeye Leaf Spot (Cercorosa sojina) symposium (Boyd Padgett, moderator)

Development of Baseline Cercospora sojina Sensitivity Levels to Quinone Outside Inhibitor Fungicides and Monitoring for Resistance. GR Zhang and CA Bradley

Soybean Pathogen Found to be Resistant to Fungicides MA Newman and CA Bradley

Strobilurin-resistant Cercospora sojina in Kentucky: Field History. D Hershman

Graduate student paper competition (Tom Allen, …

The Sugar Sensor, Trehalose-6-Phosphate Synthase (Tps1), Regulates Primary And Secondary Metabolism During Infection By The Rice Blast Fungus: Will Magnaporthe Oryzae’S “Sweet Tooth” Become Its “Achilles’ Heel”?, Jessie Fernandez, Richard A. Wilson

Fungal Molecular Plant-Microbe Interactions

Rice blast disease is considered one of the most serious diseases of cultivated rice and is mediated by the causal agent, Magnaporthe oryzae. During infection, dome-shaped fungal cells, called appressoria, form on the surface of the leaf and generate turgor through the accumulation of glycerol. This enormous pressure is directed down onto a thin penetration hypha emerging from the base of the cell, forcing it through the surface of the rice leaf and allowing fungal colonization of the plant interior. The non-reducing disaccharide, trehalose, is present in conidia of M. oryzae and is mobilized during appressorium formation. The first step …

Delivery Of Prolamins To The Protein Storage Vacuole In Maize Aleurone Cells, Francisca C. Reyes, Taijoon Chung, David Holding, Rudolf Jung, Richard Vierstra, Marisa S. Otegui

Center for Plant Science Innovation: Faculty Publications

Zeins, the prolamin storage proteins found in maize (Zea mays), accumulate in accretions called protein bodies inside the endoplasmic reticulum (ER) of starchy endosperm cells. We found that genes encoding zeins, a-globulin, and legumin-1 are transcribed not only in the starchy endosperm but also in aleurone cells. Unlike the starchy endosperm, aleurone cells accumulate these storage proteins inside protein storage vacuoles (PSVs) instead of the ER. Aleurone PSVs contain zeinrich protein inclusions, a matrix, and a large system of intravacuolar membranes. After being assembled in the ER, zeins are delivered to the aleurone PSVs in atypical prevacuolar compartments …

Plant Targets For Pseudomonas Syringae Type Iii Effectors: Virulence Targets Or Guarded Decoys?, Anna Block, James R. Alfano

Center for Plant Science Innovation: Faculty Publications

The phytopathogenic bacterium Pseudomonas syringae can suppress both pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) by the injection of type III effector (T3E) proteins into host cells. T3Es achieve immune suppression using a variety of strategies including interference with immune receptor signaling, blocking RNA pathways and vesicle trafficking, and altering organelle function. T3Es can be recognized directly or indirectly by resistance proteins monitoring specific T3E targets resulting in ETI. It is presently unclear whether the monitored targets represent bona fide virulence targets or guarded decoys. Extensive overlap between PTI and ETI signaling suggests that T3Es may suppress …

The N-Terminal Region Of Wheat Streak Mosaic Virus Coat Protein Is A Host- And Strain-Specific Long-Distance Transport Factor, Satyanarayana Tatineni, David H. Van Winkle, Roy French

Department of Plant Pathology: Faculty Publications

Understanding the genetics underlying host range differences among plant virus strains can provide valuable insights into viral gene functions and virus-host interactions. In this study, we examined viral determinants and mechanisms of differential infection of Zea mays inbred line SDp2 by Wheat streak mosaic virus (WSMV) isolates. WSMV isolates Sidney 81 (WSMV-S81) and Type (WSMV-T) share 98.7% polyprotein sequence identity but differentially infect SDp2: WSMV-S81 induces a systemic infection, but WSMV-T does not. Coinoculation and sequential inoculation of SDp2 with WSMV-T and/or WSMV-S81 did not affect systemic infection by WSMV-S81, suggesting that WSMV-T does not induce a restrictive defense response …

Co-Culture Of Yeast Antagonists Of Fusarium Head Blight And Their Effect On Disease Development In Wheat, D. A. Schisler, P. J. Slininger, Michael J. Boehm, P. A. Paul

Department of Plant Pathology: Faculty Publications

Multistrain mixtures of biocontrol agents which can reduce plant disease to a greater extent than the individual strains of the mixture, commonly, are prepared by blending separately produced fermentation products. Co-cultivation of strains to equivalent biomass yields would provide mixture advantages without incurring the cost disadvantages of multiple fermentation and processing protocols. Fusariwn Head Blight (FHB) antagonists Cryptococcus flavescens OR 182.9 (NRRL Y-302l6), C. aureus OH 181.1 (NRRL Y-302l5) and C. aureus OR 181.1 (NRRL Y -30215), were grown in two- and three-strain co-cultures to assess the quality and efficacy of the fermentation end products produced. Final cell counts of …

The Gc-Rich Mitochondrial And Plastid Genomes Of The Green Alga Coccomyxa Give Insight Into The Evolution Of Organelle Dna Nucleotide Landscape, David Roy Smith, Fabien Burki, Takashi Burki, Jane Grimwood, Igor V, Grigoriev, James L. Van Etten, Patrick J. Keeling

Department of Plant Pathology: Faculty Publications

Most of the available mitochondrial and plastid genome sequences are biased towards adenine and thymine (AT) over guanine and cytosine (GC). Examples of GC-rich organelle DNAs are limited to a small but eclectic list of species, including certain green algae. Here, to gain insight in the evolution of organelle nucleotide landscape, we present the GC-rich mitochondrial and plastid DNAs from the trebouxiophyte green alga Coccomyxa sp. C-169. We compare these sequences with other GC-rich organelle DNAs and argue that the forces biasing them towards G and C are nonadaptive and linked to the metabolic and/or life history features of this …

Minimal Art: Or Why Small Viral K+ Channels Are Good Tools For Understanding Basic Structure And Function Relations, Gerhard Thiel, Dirk Baumeister, Indra Schroeder, Stefan M. Kast, James L. Van Etten, Anna Moroni

James Van Etten Publications

Some algal viruses contain genes that encode proteins with the hallmarks of K+ channels. One feature of these proteins is that they are less than 100 amino acids in size, which make them truly minimal for a K+ channel protein. That is, they consist of only the pore module present in more complex K+ channels. The combination of miniature size and the functional robustness of the viral K+ channels make them ideal model systems for studying how K+ channels work. Here we summarize recent structure/function correlates from these channels, which provide insight into functional properties such as gating, pharmacology and …

Managing Crop Diseases With Fungicides, Kay Ruden, Lawrence E. Osborne

SDSU Extension Fact Sheets

This guide contains a list of fungicides labeled for use in South Dakota at the time of publication. The list is dynamic and prone to frequent changes. It therefore should not be considered as a substitute for label information. Always read and follow label directions for approved uses of these products, and check with the South Dakota Department of Agriculture for up-to-date product registration information.

Structural And Functional Analysis Of The Type Iii Secretion System From Pseudomonas Fluorescens Q8r1-96, Dmitri V. Mavrodi, Anna Joe, Olga V. Mavrodi, Karl A. Hassan, David M. Weller, Ian T. Paulsen, Joyce E. Loper, James R. Alfano, Linda S. Thomashow

Center for Plant Science Innovation: Faculty Publications

Pseudomonas fluorescens Q8r1-96 represents a group of rhizosphere strains responsible for the suppressiveness of agricultural soils to take-all disease of wheat. It produces the antibiotic 2,4-diacetylphloroglucinol and aggressively colonizes the roots of cereal crops. In this study, we analyzed the genome of Q8r1-96 and identified a type III protein secretion system (T3SS) gene cluster that has overall organization similar to that of the T3SS gene cluster of the plant pathogen Pseudomonas syringae. We also screened a collection of 30 closely related P. fluorescens strains and detected the T3SS genes in all but one of them. The Q8r1-96 genome contained …

Mpk6, Sphinganine And The Lcb2a Gene From Serine Palmitoyltransferase Are Required In The Signaling Pathway That Mediates Cell Death Induced By Long Chain Bases In Arabidopsis, Mariana Saucedo-García, Arturo Guevara-Garcia, Ariadna González-Solís, Felipe Cruz-García, Sonia Vázquez-Santana, Jennifer E. Markham, M. Guadalupe Lozano-Rosas, Charles R. Dietrich, Maricela Ramos-Vega, Edgar B. Cahoon, Marina Gavilanes-Ruíz

Center for Plant Science Innovation: Faculty Publications

• Long chain bases (LCBs) are sphingolipid intermediates acting as second messengers in programmed cell death (PCD) in plants. Most of the molecular and cellular features of this signaling function remain unknown.

• We induced PCD conditions in Arabidopsis thaliana seedlings and analyzed LCB accumulation kinetics, cell ultrastructure and phenotypes in serine palmitoyltransferase (spt), mitogen-activated protein kinase (mpk), mitogenactivated protein phosphatase (mkp1) and lcb-hydroxylase (sbh) mutants.

• The lcb2a-1 mutant was unable to mount an effective PCD in response to fumonisin B1 (FB1), revealing that the LCB2a gene is essential for the …