Plant Pathology Commons^™

Rna-Seq Based Analysis Of Population Structure Within The Maize Inbred B73, Zhikai Liang, James C. Schnable

Center for Plant Science Innovation: Faculty Publications

Recent reports have shown than many identically named genetic lines used in research around the world actually contain large amounts of uncharacterized genetic variation as a result of cross contamination of stocks, unintentional crossing, residual heterozygosity within original stocks, or de novo mutation. 27 public, large scale, RNA-seq datasets from 20 independent research groups around the world were used to assess variation within the maize (Zea mays ssp. mays) inbred B73, a four decade old variety which served as the reference genotype for the original maize genome sequencing project and is widely used in genetic, genomic, and phenotypic research. Several …

Antiviral Rna Silencing Suppression Activity Of Tomato Spotted Wilt Virus Nss Protein, Tania Ocampo Ocampo, Sergio M. Gabriel Peralta, Nicole Bacheller, Stella Uiterwaal, Aaron Knapp, Alanna Hennen, Daniel Leobardo Ochoa-Martínez, Hernan Garcia-Ruiz

Department of Plant Pathology: Faculty Publications

In addition to regulating gene expression, RNA silencing is an essential antiviral defense system in plants. Triggered by double-stranded RNA, silencing results in degradation or translational repression of target transcripts. Viruses are inducers and targets of RNA silencing. To condition susceptibility, most plant viruses encode silencing suppressors that interfere with this process, such as the Tomato spotted wilt virus (TSWV) NSs protein. The mechanism by which NSs suppresses RNA silencing and its role in viral infection and movement remain to be determined. We cloned NSs from the Hawaii isolate of TSWV and using two independent assays show for the first …

Description Of Mesocriconema Ericaceum N. Sp. (Nematoda: Criconematidae) And Notes On Other Nematode Species Discovered In An Ericaceous Heath Bald Community In Great Smoky Mountains National Park, Usa, Thomas O. Powers, Peter Mullin, Rebecca Higgins, Timothy Harris, Kirsten S. Powers

Department of Plant Pathology: Faculty Publications

A new species of Mesocriconema and a unique assemblage of plant-parasitic nematodes was discovered in a heath bald atop Brushy Mountain in Great Smoky Mountains National Park. Mesocriconema ericaceum n. sp., a species with males, superficially resembles M. xenoplax. DNA barcoding with the mitochondrial COI gene provided evidence of the new species as a distinct lineage. SEM revealed significant variability in arrangement of labial submedian lobes, plates, and anterior and posterior annuli. Three other nematodes in the family Criconematidae were characterized from the heath bald. Ogma seymouri, when analyzed by statistical parsimony, established connections with isolates from north-eastern Atlantic …

Exploration Of Chemical And Biological Management Strategies For Diaphorina Citri The Primary Vector Of Candidatus Liberibacter Asiaticus, Gretta Marie Sharp

Biology Theses

Diaphorina citri (Hemipteran: Psyllidae), the Asian citrus psyllid, is a phloem-feeding, invasive species endemic to southern Asia that was first identified in the United States in Florida in 1998. Since introduction, D. citri has spread across the major citrus growing regions of the United States. This is of great concern to the citrus industry because D. citri is the primary vector of Candidatus Liberibacter asiaticus the causal agent of Haunglongbing (HLB). Haunglongbing is the most economically devastating disease of citrus causing an estimated 8.92 billion dollars lost in revenue and 4.62 billion dollars lost in gross domestic product between 2006-2007 …

Investigating Novel Approaches For The Integrated Control Of The Soilborne Strawberry Pathogens Macrophomina Phaseolina And Fusarium Oxysporum F. Sp. Fragariae, Mel Carter

Master's Theses

Macrophomina phaseolina (Mp) and Fusarium oxysporum f. sp. fragariae (Fof) are emerging soilborne pathogens causing crown rot and Fusarium wilt, respectively, in commercial strawberry production in California. Fungicides representing eight active ingredients from four different mode of action groups (FRAC groups 1, 3, 7 and 12) were evaluated for their efficacy against each pathogen in vitro and each disease in planta. Fungicide active ingredients were evaluated for their ability to inhibit mycelial growth of both pathogens in vitro. Half-strength potato dextrose agar was amended with six different concentrations (0.01, 0.1, 1.0, 5.0, 10, 50 µg …

Genetic Engineering And Sustainable Crop Disease Management: Opportunities For Case-By-Case Decision-Making, Paul Vincelli

Plant Pathology Faculty Publications

Genetic engineering (GE) offers an expanding array of strategies for enhancing disease resistance of crop plants in sustainable ways, including the potential for reduced pesticide usage. Certain GE applications involve transgenesis, in some cases creating a metabolic pathway novel to the GE crop. In other cases, only cisgenessis is employed. In yet other cases, engineered genetic changes can be so minimal as to be indistinguishable from natural mutations. Thus, GE crops vary substantially and should be evaluated for risks, benefits, and social considerations on a case-by-case basis. Deployment of GE traits should be with an eye towards long-term sustainability; several …

A Brief History Of Corn: Looking Back To Move Forward, Jon Derek Pruitt

Doctor of Plant Health Program: Dissertations and Student Research

Maize was domesticated from teosinte in Mexico some 7,000 to 10,000 years ago and quickly spread through the Americas. It has become one of the most important crops at a local and global level. Two types, Northern Flint corn and Southern Dent corns provided the basis of the genetic background of modern maize hybrids. The development of hybrids, first double-cross and later single-cross hybrids, along with a transition to high input farming provided huge yield increases, which have continued to improve with improving technology.

Increase in maize production also caused a rise in Western corn Rootworm (Diabrotica virgifera virgifera …

Screening Strawberry Clones For Anthracnose Disease Resistance Using Traditional Techniques And Molecular Markers, Melinda A. Miller-Butler

Dissertations

Cultivated strawberry, Fragaria x ananassa Duchesne, is host for many pathogens. One of the most destructive diseases of strawberry is anthracnose, whose symptoms include fruit rot, leaf and petiole lesions, crown rot, wilt, and death. Three species of Colletotrichum are considered causative agents of anthracnose diseases of strawberry. Colletotrichum acutatum causes anthracnose fruit rot, has a broad host range, and occurs in most areas of the world where strawberries are grown. Colletotrichum fragariae, the primary causal fungus of anthracnose crown rot, may infect all aboveground parts of the strawberry plant, and has restricted host and geographic ranges. Colletotrichum gloeosporioides …

Genetic Analysis Of Soybean Mosaic Virus (Smv) Resistance Genes In Soybean [Glycine Max (L.) Merr.], Mariola Klepadlo

Graduate Theses and Dissertations

Soybean mosaic virus (SMV) causes the most serious viral disease in soybean worldwide. Seven SMV strains, G1 - G7, and three independent multi-allelic loci for SMV resistance, Rsv1, Rsv3, and Rsv4, have been identified. In the initial study, 299 soybean germplasm lines were genotyped for Rsv4 region, inoculated with SMV-G1 and G7 strains, and classified into several resistance groups. The Glyma.02g121400 locus was sequenced from ten soybean accessions, and alignment of the sequences revealed three SNPs displaying 100% polymorphic consistency when a soybean genotype carrying the Rsv4 gene was present. A cross between V94-5152 × Lee 68 was made to …

Microbe-Id: An Open Source Toolbox For Microbial Genotyping And Species Identification, Javier F. Tabima, Sydney E. Everhart, Meredith M. Larsen, Alexaandra J. Weisberg, Zhian N. Kamvar, Mathew A. Tancos, Christine D. Smart, Jeff H. Chang, Niklaus J. Grünwald

Department of Plant Pathology: Faculty Publications

Development of tools to identify species, genotypes, or novel strains of invasive organisms is critical for monitoring emergence and implementing rapid response measures. Molecular markers, although critical to identifying species or genotypes, require bioinformatic tools for analysis. However, user-friendly analytical tools for fast identification are not readily available. To address this need, we created a web-based set of applications called Microbe-ID that allow for customizing a toolbox for rapid species identification and strain genotyping using any genetic markers of choice. Two components of Microbe-ID, named Sequence-ID and Genotype-ID, implement species and genotype identification, respectively. Sequence-ID allows identification of species by …

Managing Drought Stress In California Agricultural Systems, Gregory D. Brittain Jr.

Doctor of Plant Health Program: Dissertations and Student Research

California is currently facing a historic drought, and this has led many farmers in the state to severely cut back on irrigation. Optimal use of water for irrigation requires a comprehensive understanding of how plants respond physiologically to water stress (Chapter 1). By monitoring water requirements in crops and managing irrigation to meet those requirements, growers can significantly reduce water use (Chapter 2). This can be done through improving application efficiency of irrigation technology as well as increasing the water use efficiency of the crops themselves. Deficit irrigation practices can be used to manipulate the physiology of water use in …

Ecological Risks Of The Conventional Insecticide/Fungicide Seed Treatment Mixture Of Thiamethoxam And Mefenoxam In Soybean On Beneficial Insects, Carolina Camargo

Department of Entomology: Dissertations, Theses, and Student Research

The impact of neonicotinoid seed treatments on beneficial insects has been a controversial topic during the last years. While neonicotinoids are usually used as mixtures with systemic fungicides, few studies have examined the impact of the mixtures on beneficial insects. Pesticide mixtures can have synergistic, additive, or antagonistic effects on the toxicity of neonicotinoids on non-target species.

Thiamethoxam with mefenoxam is the most used neonicotinoid insecticide/fungicide mixture applied to soybean. Based on the systemic nature of thiamethoxam and mefenoxam, residues of this insecticide/fungicide mixture can be present in soybean vegetative and floral tissue with potential impacts to beneficial insects. This …

A Vision For Extension: Case Studies On Managing Extreme Weather Challenges In Corn, Anthony J. Mcmechan

Doctor of Plant Health Program: Dissertations and Student Research

Global demand for corn is projected to rise in the coming decades to meet the food and fuel requirements of an increasing human population. Technological innovations have significantly improved corn yields over the past few decades; however, corn production is continually limited by unfavorable weather conditions. Extreme weather events put pressure on producers, adjustors, and consultants to make quick management decisions to maintain the highest return on their investment. Proper management decisions require an understanding of plant response and practical ways of applying this knowledge under real world conditions.

The following document was written after completing a six-month internship at …

Root Hydraulic Conductance In Malosma Laurina Experiencing Severe Dieback In The Santa Monica Mountains, Natalie M. Aguirre 5861995, Avery Davis, Sarah Nelson

Seaver College Research And Scholarly Achievement Symposium

Malosma laurina is a dominant species in coastal chaparral ecosystems The deep root systems of M. laurina provide structural support for the steep Santa Monica Mountains and allow M. laurina to tap into the deep water table. M. laurina dieback is prevalent in coastal exposures of the SMM, presumably due to historic drought predisposing plant tissues to infection by the fungal pathogen Botryosphaeria dothidea. In ecosystems that experience annual dry periods, a high hydraulic conductance in roots is necessary to provide plants with sufficient water. A recent study has examined the effect of Botryosphaeria on the hydraulic conductance of M. …

Stenocarpella Maydis: Identification, Management, And Population Diversity, Martha P. Romero Luna

Open Access Dissertations

Diplodia ear rot (DER) has been a persistent corn disease across the Midwest, and in recent years it has become an annual problem. The objectives of this study were to i) develop a molecular assay for the identification of Stenocarpella maydis, causal agent of DER, ii) evaluate the effect of crop rotation and tillage on DER severity, iii) determine the survival period of S. maydis in corn residue at different soil depths in a corn field, and iv) identify genetic diversity among S. maydis isolates collected from the Midwestern and Southern United States. The genus Stenocarpella contains two species, S. …

Molecular Mechanisms Of Goss’S Wilt, Samuel Eastman, Guangyong Li, Fan Yang, Josh Herr, James R. Alfano

UCARE: Research Products

Clavibacter michiganensis subsp. Nebraskensis (Cmn) is a pathogen responsible for Goss’s Wilt in maize in the high plains. Strains of Clavibacter michiganensis subsp. Nebraskensis that are virulent and non-virulent in maize have been isolated, but the mechanism of this differentiation is not understood. Investigation of the genetic differences between virulent and non-virulent strains is providing an explanation as to how Cmn causes disease. Cmn mutants with reduced or removed virulence have been created using Tn5 transposon transformation to randomly knockout virulence factors. Potential effectors have also been identified in a genomic “virulence island” region by using bioinformatics.

Regeneration And Transformation Of Common Bean (Phaseolus Vulgaris L.), Iqbal Singh

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

Common bean is the most important grain legume for direct human consumption and serves as main source of dietary protein for millions of people in developing world. Genetic transformation methods can serve as an important tool to complement traditional plant breeding methods for common bean improvement. Low transformation frequencies and unstable genetic integration associated with biolistic methods limits its use for routine transformation of common bean. In an attempt to develop Agrobacterium tumefaciens mediated transformation protocol for common bean, potential of primary leaves as an explant was analyzed following unsuccessful results with other tissues. Primary leaf explants were prepared from …

The Function Of A Putative Sumo E2 Enzyme In Plant Immunity, Huan Zhang

UCARE: Research Products

SUMO proteins are small ubiquitin-like modifiers. They can be attached to a target protein through a process called SUMOylation that involves an enzymatic cascade catalyzed by SUMO E1 (activating enzyme), E2 (conjugating enzyme) and E3 (ligation enzyme). Similar to ubiquitination, SUMOylation has been found in recent years to play a role in the regulation of pathogen-host ”arms race” (Chen, A. J., et al., 2013). However, the molecular mechanism behind the regulation is largely unexplored. To date, only ONE SUMO E2, UBC9 has been identified and confirmed to catalyze SUMOylation in human cell (Motion, G. B, et al., 2015). Nevertheless, recently …

Role Of Viral Rna And Co-Opted Cellular Escrt-I And Escrt-Iii Factors In Formation Of Tombusvirus Spherules Harboring The Tombusvirus Replicase, Nikolay Kovalev, Isabel Fernández De Castro Martín, Judit Pogany, Daniel Barajas, Kunj Bihari Pathak, Cristina Risco, Peter D. Nagy

Plant Pathology Faculty Publications

Plus-stranded RNA viruses induce membrane deformations in infected cells in order to build viral replication complexes (VRCs). Tomato bushy stunt virus (TBSV) co-opts cellular ESCRT (endosomal sorting complexes required for transport) proteins to induce the formation of vesicle (spherule)-like structures in the peroxisomal membrane with tight openings toward the cytosol. In this study, using a yeast (Saccharomyces cerevisiae) vps23Δ bro1Δ double-deletion mutant, we showed that the Vps23p ESCRT-I protein (Tsg101 in mammals) and Bro1p (ALIX) ESCRT-associated protein, both of which bind to the viral p33 replication protein, play partially complementary roles in TBSV replication in cells …

Functional And Structural Analysis Of Fst1 In Fusarium Verticillioides, Chenxing Niu

Open Access Dissertations

Fusarium verticillioides causes an important seed disease on maize and produces fumonisin B1 (FB1), a mycotoxin that is detrimental to human and animal health. Previous studies discovered that expression of FST1 is required for FB1 production and wild-type level of virulence on maize seeds. FST1 encodes a putative protein with 12 transmembrane domains with sequence similarity to hexose transporters. However, those studies have failed to prove its ability to transport glucose, fructose or mannose. I identified another three phenotypes associated with the lack of a functional FST1, which includes reduced hydrophobicity of hyphae, reduced macroconidia production, and increased sensitivity to …