Life Sciences Commons^™

Fungicide Sensitivity, Race Structure, And Host Pathogenicity Of Phytophthora Nicotianae In Tennessee And North Carolina, Taylor Giovanna Miller

Masters Theses

Phytophthora nicotianae, a hemibiotrophic oomycete, is the causal agent of disease of over 300 hosts, notably tobacco, tomato, citrus, strawberry, and ornamentals. Black shank of tobacco is a devastating disease that can result in up to 100% yield loss if left untreated, and buckeye rot of tomato compromises the marketability and yield of fruit impacted by P. nicotianae. Black shank and buckeye rot have been reported throughout the state of Tennessee, and the goal of this work was to analyze fungicide sensitivity of P. nicotianae isolated from tobacco and tomato, characterize the race structure of P. nicotianae, …

Screening For Binding Partners And Protein-Protein Interactions Of A Fungal Transcription Factor- Xdr1, Nishadi Punsara Gallala Gamage

Masters Theses

Clarireedia spp. (formerly Sclerotinia homoeocarpaF.T. Bennett) is the causal agent dollar spot, the most economically important turfgrass disease impacting golf courses in North America. The most effective strategy for dollar spot control is repeated application of multiple classes of fungicides. However, reliance on chemical application has led to resistance to four classes of fungicides as well as multidrug resistance (MDR). Fungi are known to detoxify xenobiotics, like fungicides, through transcriptional regulation of three detoxification phases: modification, conjugation and secretion. Little is known, however, of the protein-protein interactions that facilitate these pathways. Following next-generation RNA sequencing of Clarireedia spp., a …

The Role Of Low-Molecular Weight Fungal Metabolites In Eutypa Dieback Grapevine Trunk Disease, Dana Sebestyen

Masters Theses

Eutypa dieback, one of several grapevine trunk diseases (GTDs), is of serious concern to the grape industry globally. This disease is caused by the fungus Eutypa lata but it is often seen in consortia growth with Phaeoacremonium minimum and Phaeomoniella chlamydospora. It is vital to understand the mechanisms for how this disease functions to develop control measures to combat it. Brown rot fungi are able to use a complex of low molecular weight (LMW) metabolites to induce a Fenton reaction to deconstruct woody tissue. These metabolites are part of a chelator mediated Fenton (CMF) chemistry that produces reactive oxygen …

Characterizing The Interaction Between Non-Pathogenic Fusarium Oxysporum And Arabidopsis Thaliana To Determine Beneficial Effects Conferred To The Model Plant Host, Kathryn Isabelle Vescio

Masters Theses

Fusarium oxysporum (Fo) is a soil-borne fungal pathogen that causes vascular wilt disease on a broad range of plants, including agricultural crops and the model plant Arabidopsis thaliana. There are non-pathogenic members of the Fo species complex that confer defense benefits against other pathogens to the host plant, however alteration to the host’s physiology through interaction with one of these strains, Fo47, have not been described. In this study, we aimed to establish the Fo47-A. thaliana interaction and determine if Fo47 reduces disease severity of a pathogenic Fo isolate, Fo5176. Additionally, we sought to use bioinformatics to mine …

Apple Disease Forecasting Models: When Climate Changes The Rules, Elizabeth W. Garofalo

Masters Theses

With a changing global climate, plant pathologists must understand the impact aberrant weather events may have on the development of plant diseases. Fungal plant infections are largely dependent on temperature and precipitation, climate parameters that are predicted to change more in this century. Venturia inaequalis causes apple scab, one of the most destructive apple diseases of temperate growing regions. Temperature and precipitation drive apple scab infections and forecast models, which guide growers in efficient, effective fungicide applications. In some recent years in the Northeast, these models have failed to accurately predict when ascospores of this fungus are available to cause …

Investigation Of Cytochrome P450 Monooxygenases In S. Homoeocarpa For Chlorothalonil Biotransformation, Robert Green

Masters Theses

Sclerotinia homoeocarpa (F.T. Bennett) is one of the most economically important pathogens on high amenity cool-season turfgrasses where it causes dollar spot. Due to decades of over-reliance and repeated chemical treatments, S. homoeocarpa has developed resistance and insensitivity to multiple classes of fungicides. To understand the genetic mechanisms of fungicide resistance, the whole genomes of two strains with varying resistance levels to fungicides, were sequenced. In unpublished data (Sang et al.), a RNA-sequencing analysis revealed three CYP450s that were validated to play a functional role in S. homoeocarpa’s resistance against different fungicide classes. We also identified CYP450 metabolic action …

Switchgrass Extractives Have Potential As A Value-Added Antimicrobial Against Plant Pathogens And Foodborne Pathogens, Alexander Ian Bruce

Masters Theses

Panicum virgatum (switchgrass), a perennial grass native to North America, is a leading biomass feedstock candidate for the manufacture of cellulosic ethanol. Switchgrass is considered a viable option for biofuel production due to its cheap production cost and ability to grow on marginal land. Biofuel derived from switchgrass has been shown to be very energy efficient, producing 540% more renewable energy versus nonrenewable energy expended. Switchgrass-derived biofuel is also estimated to have greenhouse gas emissions that are 94% lower than emissions from gasoline (Schmer et al 2008). Biofuels are created through biochemical processes that utilize various enzymes and microorganisms for …

Characterization Of Fusarium Species And Alternaria Alternata, And Their Effects On Switchgrass Health And Chemical Components, Sara Beth Collins

Masters Theses

Panicum virgatum L., readily referred to as Switchgrass, is a perennial warm-season bunch grass, used as an alternative energy source for biofuel production. There is insufficient research on switchgrass pathogens, and is expected that an increase in disease pressure will result as more land is reserved for this perennial crop. The purpose of this research was to identify and characterize pathogenic Alternaria alternata and Fusarium species on Switchgrass (Panicum virgatum L.), and to evaluate their impact on stand establishment and plant health. Molecular identifications of fungal isolates obtained from infected commercial switchgrass seed yielded eight species (A. alternata, …

Rapid Molecular Detection And Population Genetics Of Pityophthorus Juglandis, A Vector Of Thousand Cankers Disease In Juglans Spp., Emel Oren

Masters Theses

Thousand Cankers Disease (TCD) is a disease complex involving the fungal pathogen Geosmithia morbida, an insect vector Pityophthorus juglandis, and the hosts, Juglans spp. and Pterocarya spp. Signs and symptoms of TCD include crown thinning due to branch dieback, yellowing and wilting of the leaves, appearance of epicormic shoots, numerous entrance/exit holes, gallery formation by P. juglandis, and the development of small, dark brown cankers underneath the bark. TCD originally described from western U.S., has now expanded to eastern U.S. and northwestern Italy. The disease complex is often difficult to diagnose due to the absence of symptoms …

Influence Of Application Technology On Foliar Fungicide Efficacy On Cercospora Sojina Infected Soybean, Shawn Alan Butler

Masters Theses

Due to the constant concern with off-target contamination and application technology requirements associated with future herbicide-tolerant crops, the use of drift-reduction nozzle technology (DRT) may increase. The primary objective of this research was to evaluate the effects of coarse droplets generated by drift-reduction nozzles on foliar fungicide efficacy and residual in soybean infected by frogeye leaf spot caused by Cercospora sojina. No differences in disease control, soybean yield, spray retention, and residual when applying Quadris Top SB, a premix of azoxystrobin and difenoconazole, using nozzles that produce either a medium or ultra coarse droplet spectrum were determined.

Due to …

Evaluation Of Fungicide Efficacy Against Cercospora Sojina And Selection For Qoi-Fungicide Resistance In Soybean, Alicia Mercedes Cochran

Masters Theses

Frogeye leaf spot (FLS) of soybean is caused by Cercospora sojina. In 2010, resistance to the quinone outside inhibitor (QoI) fungicides was reported. Since then, evaluating FLS for QoI-resistance has been of particular interest in Tennessee and other soybean-producing states. In order to determine alternative fungicide options, fungicides with solo and combination mode of action were tested in 2013-2014. The objectives were,1) to evaluate fungicide efficacy for disease control and yield protection, and 2) evaluate selection pressure for QoI-resistance. Treatments included the following fungicide groups: QoI, DMI, MBC, Chlorothalonil, QoI+DMI, SDHI+QoI, SDHI+QoI+DMI, and DMI+MBC. QoI and Chlorothalonil treatments failed …

Potential Interaction Between Pre- And Post-Emergence Herbicides And The Efficacy Of Insecticide And Fungicide Seed Treatments In Cotton, Cory Joseph Vineyard

Masters Theses

An apparent reduction in the performance of neonicotinoid seed treatments in controlling thrips, especially in cotton, has been observed, which has coincided with the increased use of both pre- and post-emergence herbicides to control glyphosate-resistant weeds. The objective of this research was to evaluate the potential interactions of both pre- and post-emergence herbicides on the efficacy of insecticide and fungicide seed treatments in cotton

Aldicarb along with imidacloprid and thiamethoxam seed treatments reduced thrips numbers compared with non-treated seed. However, thiamethoxam did not provide effective control. Some pre-emergence herbicide treatments reduced plant health. While there was evidence that thrips injury …

Population Structure Of Late Blight (Phytophthora Infestans) In Colombia And Ecuador And Downy Mildew (Peronospora Farinosa F. Sp. Spinaciae) On Spinach In Arizona And California, Rebecca Marie Lyon

Masters Theses

In this study, Phytophthora infestans and Peronospora farinosa f. sp. spinaciae populations were analyzed using single nucleotide polymorphisms (SNPs). In Ecuador and Colombia, Phytophthora infestans causes significant damage to potato and tomato and the epidemiology is known to be highly clonal. Our objective was to measure population structure within the context of this clonal epidemiology using both synonymous and nonsynonymous markers. Candidate SNP sites were selected by comparing the draft genomes of the Ecuadorian isolates EC1-3527 and EC1-3626. Genotypes were assessed directly from infected tissue using a targeted sequencing approach. A total of 54 polymorphic sites were assessed in 93 …

The Performance Of Bacterial Phytosensing Transgenic Tobacco Under Field Conditions, Michael Harrison Fethe

Masters Theses

Currently the platforms for wide-area detection of environmental contamination are limited. Therefore, there is interest in developing new platforms, especially for use in crop plants to detect and report the presence of biotic and abiotic stress agents. A biosensor uses a biological organism or substrate to detect the presence of an elicitor (i.e., heavy metal, TNT, or bacteria). The foundational groundwork to create biosensors in transgenic plants exists. The creation of bacterial phytosensing transgenic tobacco containing an orange fluorescent protein (OFP) reporter driven by synthetic pathogen-inducible promoters provides a fluorescent signal when infected with phytopathogens for earlier detection in the …

The Effect Of Photocatalytic Titanium Dioxide And Ultraviolet B Radiation On Sclerotinia Homoeocarpa Growth And Pathogenicity, Chun Hu

Masters Theses

Photocatalytic TiO₂ [titanium dioxide] generates strong oxidative effects when illuminated with ultraviolet (UV) light with wavelengths of less than 385 nm. UVB has wavelengths ranging from 280 to 315nm. Previous research indicates the oxidative species and UVB radiation can react and cause cellular damage to microorganisms, which may reduce Sclerotinia homoeocarpa growth and help to control dollar spot disease development. The objectives of this study were to investigate the interactions of TiO₂ and UVB radiation, both in vitro and in vivo, on the growth and development of dollar spot. Factorial treatments consisting of five rates of TiO₂ and three doses …

The Life History And Control Of Pityophthorus Juglandis Blackman On Juglans Nigra L. In Eastern Tennessee, Katheryne Avery Nix

Masters Theses

In the last decade, western states have experienced an increasing mortality rate in Juglans nigra L., black walnut, as a result of the fungal species Geosmithia morbida Kolařík et al. that results in numerous cankers that girdle the branches, resulting in dieback and tree mortality. The only known vector of G. morbida is the walnut twig beetle (WTB), Pityophthorus juglandis Blackman. This newly recognized disease/insect complex has been named Thousand Cankers Disease (TCD) due to the quantity of cankers produced by G. morbida.

Recently, TCD was discovered in the eastern U.S. To limit the spread of TCD in eastern …

Compatibility Of Essential Oils With The Biocontrol Fungus, Beauveria Bassiana, Wanjing Liu

Masters Theses

The tomato seedling damping-off pathogens Rhizoctonia and Pythium have the potential to cause severe loss in the greenhouse and field. Both seed application of Beauveria bassiana and soil amendment with bioactive monarda herbages are sustainable approaches that can play a role in suppressing damping-off of tomato seedlings. The objectives of this research were to determine the compatibility of essential oils and B. bassiana, and to determine the impact of the two when used together as a seed treatment in greenhouse experiments.

Different concentrations of five essential oils that were active against damping-off pathogens (cymene, carvacrol, thymol, borneol, and geraniol) …

Anaerobic Soil Disinfestation: Evaluation Of Anaerobic Soil Disinfestation (Asd) For Warm-Season Vegetable Production In Tennessee, David Grant Mccarty

Masters Theses

Anaerobic soil disinfestation (ASD) is a non-chemical, pre-plant soil treatment recently developed for control of pests such as soilborne plant pathogens, plant-parasitic nematodes, and weeds in specialty crop systems. Soil treatment by ASD includes incorporating a labile carbon (C) source, tarping with plastic, and irrigation of the topsoil to saturation to facilitate the development of strongly anaerobic soil conditions driven by soil microbes. Processes occurring during the anaerobic decomposition of the added C source have been reported control plant pests. The goal of this project was to evaluate and adapt the ASD procedure to environmental conditions and production systems in …

The Epidemiology Of Puccinia Emaculata (Rust) In Switchgrass And Evaluation Of The Mycoparasite Sphaerellopsis Filum As A Potential Biological Control Organism For Switchgrass Rust., Jonathan Allen Black

Masters Theses

Switchgrass (Panicum virgatum L.) is a warm-season, perennial grass, whose native range includes the entire United States and north into Canada, excluding areas along the pacific coast. Recently, symptoms and signs of rust disease (Puccinia emaculata) have been observed on agronomic switchgrass, which include chlorosis of leaf tissue, necrosis, lodging, and plant death.

To evaluate disease progress of switchgrass rust, in four fields, individual leaves of twenty-five switchgrass plants were rated once per week for fifteen weeks over two growing seasons for disease severity. Rust was first observed on Julian day 166 and 152 in 2010 and …

Applicability Of Pigment Compounds For Reducing Light Stress In Bentgrass, Gregory Keith Bartley

Masters Theses

Chlorinated copper phthalocyanine (Signature) and pulverized cells of Chlorella vulgaris (Chlorella) were evaluated in a controlled environment for their ability to act as photoprotectants under supraoptimal levels of ultraviolet (UV) and photosynthetically active radiation (PAR) when applied to plant leaves. Plant pigment changes were documented using High Performance Liquid Chromatography following 1 week of exposure to supraoptimal light in two separate experiments incorporating UV (106.6 μmol m-2 s-1) and PAR (760.6 μmol m-2 s-1) over a 12h photoperiod. Supraoptimal levels of UV and PAR light were found to cause significant reductions in Agrostis palustris chlorophyll and carotenoid leaf pigment levels. …

Investigation Of Phytophthora Species: Phytophthora Colocasiae On Taro And Phytophthora Recovered From Streams In Eastern Tennessee, Sandesh Kumar Shrestha

Masters Theses

Oomycetes, also known as water molds, are morphologically similar to fungi. Unlike fungi, they are diploid and more closely related to plants. Several oomycetes are pathogenic to plants as well as aquatic animals. Members of the genus Phytophthora are a threat to many economically important crops and natural forest systems. The research presented in this thesis addresses intraspecific and interspecific variation in natural populations of Phytophthora. Chapter two summarizes genetic diversity and population structure for Phytophthora colocasiae attacking taro in Hawaii, Vietnam and Hainan Island, China based on novel single nucleotide polymorphism (SNP) markers. Phytophthora colocasiae causes Taro Leaf Blight, …

Abiotic And Biotic Stress Tolerance In Wheat: The Role Of Arbuscular Mycorrhizal Fungi, Marei Mahmoud Abdelkarim

Masters Theses

Rhizospheres of crop plants are complexes of chemical and microbial interactions. Many plants produce allelochemicals, substances that inhibit growth of other plants and microorganisms. In previous research, colonization of Echinacea purpurea by beneficial mycorrhizal fungi appeared to alleviate the effects of allelochemicals on the growth and the development of the medicinal herb (Gualandi, 2010). The overall aims of the work reported here were to determine if colonization by arbuscular mycorrhizal fungi (AMF) alters responses of common wheat (Triticum aestivum) to abiotic [allelopathic effects of sorghum (Sorghum bicolor)] and biotic [bird-cherry oat aphid (Rhopalosiphum padi) …

Prevalence Of Copper Resistance Among Foliar Bacterial Pathogens Of Tomato In Tennessee, Jonathon Thomas Mixon

Masters Theses

Foliar bacterial diseases are among the most important diseases of tomato. Bacterial spot is caused by four species: Xanthomonas euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri, hereafter referred to as Xanthomonas spp. Bacterial speck is caused by Pseudomonas syringae pv. tomato and bacterial canker is caused by Clavibacter michiganensis subsp. michiganensis. Fixed copper products are relied upon extensively for control, due to a lack of effective and economical alternatives. Copper resistance in bacterial spot and speck pathogens has been reported worldwide. Copper resistance quite likely exists in Tennessee, but the extent has never been …

Infection Process Of Discula Destructiva, The Causal Agent Of Dogwood Anthracnose, And Resistance Mechanism Of Flowering Dogwood, Qunkang Cheng

Masters Theses

Discula destructiva, the causal agent of dogwood anthracnose, has caused severe mortality in dogwood over the last 30 years. Although considerable research has been done with dogwood anthracnose, the infection process by D. destructiva is still obscure. A resistant cultivar of Cornus florida, ‘Appalachian Spring’, was discovered and released by the Tennessee Agricultural Experiment Station. However, the resistance mechanisms are unknown. The objectives of this research were 1) to determine the sequence of events in the infection process of D. destructiva in C. florida and 2) to determine how host resistance affects infection events of D. …

Non-Target Effect Of Imidacloprid On The Predatory Arthropod Guild On Eastern Hemlock, Tsuga Canadensis (L.) Carriere, In The Southern Appalachians, Abdul Hakeem

Masters Theses

Imidacloprid, a neonicotinoid insecticide, is commonly applied on eastern hemlock to reduce populations of Hemlock woolly adelgid (HWA). A large number of other herbivorous and transient insects also are associated with eastern hemlock. These herbivorous insects may acquire imidacloprid through feeding on treated plants. Predatory insects may acquire imidacloprid when they feed on insecticide-contaminated prey. To investigate this phenomenon, a study was conducted at Indian Boundary Campground, Cherokee National Forest, 2005-2007. This study was conducted to: 1) ascertain the effect of imidacloprid used against HWA on the predatory guild associated with eastern hemlock, 2) determine seasonal abundance of the predatory …

A Revision Of Tomoceridae (Insecta: Collembola) In Great Smoky Mountains National Park And Southern Appalachians Using Morphological And Molecular Approaches, Kelly Lynn Felderhoff

Masters Theses

Large, heavily scaled tomocerid springtails (Collembola) are abundant in eastern forests, and are important components of the detrital food web. The genus Pogonognathellus predominates in the southern Appalachians While a number of well-delimited tomocerid species have been described, others have vague morphological boundaries and appear to be species complexes. Before this study began in 2005, four species were known to occur in Great Smoky Mountains National Park (GSMNP) and the surrounding Appalachians (P. bidentatus, dubius, elongatus, flavescens). Also occurring throughout the area is Tomocerus lamellifera, a widespread and distinctive species. The goals of this project were to …

Life History Of Hemlock Woolly Adelgid, Adelges Tsugae Annand, On Eastern Hemlock, Tsuga Canadensis (L.) Carriere, In The Southern Appalachians And Assessment Of Egg Releases Of Sasajiscymnus Tsugae (Sasaji And Mcclure) For Its Management, Isaac K. Deal

Masters Theses

Studies were conducted in 2005 and 2006 at Baxter Orchard, Great Smoky Mountains National Park, Tennessee to optimize survival of Sasajiscymnus tsugae (St) (Sasaji and McClure) released as eggs on eastern hemlock, Tsuga canadensis (L.) Carriere, for biological control of Adelges tsugae (HWA) Annand. Studies investigated annual abundance and seasonality of HWA lifestages, weekly field and laboratory survival of St, and survival of St egg cohorts of various ages and densities. HWA was determined to be bivoltine on eastern hemlock in Tennessee with an aestivation period between July and October. Lifestages preferred as food by St were present from …

Cultural Control Methods That Effect The Development And Spread Of Corynespora Cassiicola (Berk. & Curt.) Wei On African Violet (Saintpaulia Ionantha Wendl.), Hillary Dawn Ross

Masters Theses

In recent years, a large commercial grower of African violets (Saintpaulia ionantha Wendl.) in middle Tennessee has experienced epidemics of Corynespora leaf spot caused by Corynespora cassiicola (Berk. & Curt.) Wei (Alan Windham, personal communication). Symptoms of Corynespora leaf spot include rapidly expanding circular lesions on the surface of the leaves and petioles. The disease occurs in propagation material and mature plants of S. ionantha which result in thousands of plants being discarded daily. The objectives of this research were to: 1) determine if irrigation methods affected disease severity, 2) to determine if fungicidal spray intervals could be extended …

Survey Of Mosquitoes In High And Low Incidence Areas For West Nile Virus In Shelby County, Tennessee With Assessment Of Parity Rates, Host Selection, And Seasonal Abundance, David M. Sanders

Masters Theses

West Nile Virus (WNV) was reported as present in ShelbyCountyin 2001 with 44 blue jays testing positive for WNV. The first reported human WNV case had an onset date of 27 July 2002. There were 40 human cases in 2002, six of which were fatal. The 2002 human cases were clustered within the I-240 beltway, the older residential area of greater ShelbyCounty. Adult mosquito collections were made from the first week in June through the first week in November for 2003 and 2004. A representative site was selected from both the high and low human WNV incidence area of ShelbyCounty, …

Seasonal Abundance Of Mosquitoes (Diptera: Culicidae) At A High And Low Prevalence Site For La Crosse Encephalitis In Eastern Tennessee, Nathan David Caldwell

Masters Theses

La Crosse (LAC), a California (CAL) serogroup bunyavirus, is the most prevalent pediatric arboviral disease in the United States and accounts for virtually all encephalitis cases associated with CAL serogroup arboviruses. In Tennessee, USA, prior to the drastic increase of confirmed La Crosse (LAC) encephalitis cases in 1997, the sum of documented cases reported to the Tennessee Department of Health totaled 9. During subsequent years in Tennessee (1997 to 2003), an average of 12 cases has been reported annually. Approximately 62% of these reported cases have occurred in the months of July and August. The native, container-inhabiting mosquito Ochlerotatus triseriatus …