Plant Pathology Commons^™

The Impact Of Fall Armyworm, Spodoptera Frugiperda (J.E. Smith), Feeding And Mechanical Defoliation On Growth And Yield Of Rice, Oryza Sativa (L.), Layton Denman Mccullars

Graduate Theses and Dissertations

The fall armyworm, Spodoptera frugiperda (J.E. Smith), (FAW) is a serious pests of many crops, and can be observed feeding throughout the entire growing season on rice, Oryza sativa, (L.). A new defoliation based threshold would help rice growers and consultants make more economically sound decisions for FAW. Work from this thesis focuses on determining the amount of damage caused by FAW feeding at different growth stages and effective insecticide seed treatments for controlling this pest.

Field plots were mechanically defoliated to determine grain yield loss across multiple growth stages and defoliation percentages. Results indicated that defoliation in late vegetative …

Factors Influencing The Spatial Distribution Of Southern Rust In Corn, Justin Bailey

Graduate Theses and Dissertations

Southern rust caused by the fungus Puccinia polysora (Underwood) is the most economically important foliar disease in corn (Zea mays) (Linnaeus) (Cyperales: Poaceae)) for Arkansas. The objective of this work was to determine distribution of southern rust in corn and to determine factors that may control its distribution.

During the 2017 and 2018 season, seven corn fields in Arkansas were rated for southern rust. After disease confirmation, fields were marked with GPS sample point locations in a grid pattern across the entire field. Ratings for disease severity were taken below, at, and above the ear leaf at each point every …

Investigating The Connection Between Light, A Circadian Clock, And Pathogenesis In Cercospora Zeae-Maydis, John Byron Ridenour

Graduate Theses and Dissertations

Gray leaf spot is a globally important foliar disease of maize caused by the fungus Cercospora zeae-maydis. In C. zeae-maydis, light is a critical environmental signal linked to pathogenesis and secondary metabolism. However, the mechanisms by which the fungus senses and responds to light are not fully understood. Thus, the overarching goal of this project was to unravel the connection between light and pathogenesis in C. zeae-maydis. The conserved fungal protein White Collar-1 (WC-1), designated Crp1 in C. zeae-maydis, senses light and initiates physiological responses. In fungi, WC-1 functions in the White Collar Complex via interaction with White Collar-2 (WC-2). …

Effect Of Soil-Applied Protoporphyrinogen Oxidase Inhibitor Herbicides On Soybean Seedling Disease, Nicholas J. Arneson

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

Seedling disease is one the most economically important diseases of soybean in the United States. It is commonly caused by Fusarium spp., Rhizoctonia solani, Pythium spp., and Phytophthora sojae, alone, or together as a disease complex. Fungicide seed treatments continue to provide the most consistent management of seedling diseases. Soil-applied protoporphyrinogen oxidase (PPO) inhibitor herbicides are used preemergence in soybean production to manage several broadleaf weeds. Applications of PPO-inhibitors can result in phytotoxic injury to soybean when environmental conditions are not favorable for soybean growth. These environmental conditions can favor seedling disease development as well. In this thesis, two …

Characterization Of Macrophomina Phaseolina Infecting Chia Plants, Cailyn Sakurai, Hagop S. Atamian, Julien Besnard

Student Scholar Symposium Abstracts and Posters

Microbial organisms have caused detrimental effects to agricultural plants by significantly decreasing their plant growth yield and it’s nutritional qualities, leading to high levels of economic losses in society. Salvia Hispanica L., commonly known as chia, is becoming a rising agricultural crop because of its favorable nutritional qualities. Chia seeds have a high concentration of α-linolenic acid, commonly known as omega-3 fatty acids) which provide several different health benefits, in addition to being a rich source of protein and fiber. Chia field trial conducted by the Atamian lab during summer 2018, experienced high levels of disease incidence characterized by …

Reporting Charcoal Rot In Chia And Developing A Susceptibility Assay, Reis M. Misaka, Hagop S. Atamian Dr., Julien Besnard Dr.

Student Scholar Symposium Abstracts and Posters

Chia (Salvia Hispanica) cross breeds were planted in the summer of 2018 with the intent of selective breeding for agricultural benefit. Preexisting pathogens in the soil caused 40-50% fatality of adult plants. This was surprising due to the precursory knowledge that chia has antibiotic and antifungal oils (Elshafie et. al. 2018); chia was only recently documented to be susceptible to Fusarium wilt (Fusarium oxysporum). The primary pathogen responsible was identified as Macrophomina phaseolina (aka charcoal rot); a widespread soilborne pathogen which has multiple commercial hosts (Su et. al. 2001).

M. phaesolina on wheat seed vector where used as …

Integrated Management Of Phytophthora Stem And Root Rot Of Soybean And The Effect Of Soil-Applied Herbicides On Seedling Disease Incidence, Vinicius Castelli Garnica

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

Soybean seedling diseases and Phytophthora stem and root rot (PSRR; caused by Phytophthora sojae) are two of the most economically important diseases in North Central U.S. Remarkable differences in disease incidence occur each year, which demonstrate that abiotic and biotic factors must interact for disease onset and development. During 2017 and 2018, field studies were conducted to (i) address the efficacy of seed treatment and genetic resistance for PSRR management on soybean population, canopy coverage (CC), and yield, and (ii) investigate potential interactions between pre-emergence (PRE) herbicides and the incidence of seedling diseases in alluvial soils in Nebraska.

Despite …

Dna Barcoding Of Pratylenchus From Agroecosystems In The Northern Great Plains Of North America, Mehmet Ozbayrak

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

Pratylenchus species are among the most common plant parasitic nematodes in the Great Plains Region. The objectives of this study were to barcode Pratylenchus specimens for species identification in the Great Plains region using mitochondrial CO1 DNA barcode. In order to (1) determine species boundaries, (2) assess the host associations of barcoded Pratylenchus, (3) to determine the distribution patterns across the Great Plains Region and, (4) to evaluate the species status of P. scribneri and P. hexincisus by a multivariate morphological analysis of haplotype groups identified by DNA barcoding. Soil samples, primarily associated with eight major crops, were collected …

Science Communication In Agriculture: The Role Of The Trusted Adviser, Lee Galen Briese

Doctor of Plant Health Program: Dissertations and Student Research

Agronomy is not simply the selling of agricultural products to farmers, nor is it the process of solving singular production problems. Agronomy is defined as the integrated, holistic perspective of agriculture (ASA, 2019) and “agronomists are specialists in crop and soil sciences, as well as ecology” (ASA, 2019). While scientific investigation and discovery are essential to understanding systems function, the tangible benefits from our knowledge stems from the application to solve problems. Clear communication is vital to successfully help stakeholders understand the importance of the science and help scientists understand the challenges stakeholders face. However, to successfully put science into …

Wheat Streak Mosaic Virus Alters The Transcriptome Of Its Vector, Wheat Curl Mite (Aceria Tosichella Keifer), To Enhance Mite Development And Population Expansion, Adarsh K. Gupta, Erin D. Scully, Nathan A. Palmer, Scott M. Geib, Gautam Sarath, Gary L. Hein, Satyanarayana Tatineni

Department of Plant Pathology: Faculty Publications

Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is an economically important wheat virus that is transmitted by the wheat curl mite (WCM; Aceria tosichella Keifer) in a persistent manner. Virus–vector coevolution may potentially influence vector gene expression to prolong viral association and thus increase virus transmission efficiency and spread. To understand the transcriptomic responses of WCM to WSMV, RNA sequencing was performed to assemble and analyse transcriptomes of WSMV viruliferous and aviruliferous mites. Among 7291 de novo-assembled unigenes, 1020 were differentially expressed between viruliferous and aviruliferous WCMs using edgeR at a false discovery rate 0.05. Differentially expressed unigenes …

Response Of Sorghum Enhanced In Monolignol Biosynthesis To Stalk Rot Pathogens, Deanna L. Funnell-Harris, Scott E. Sattler, Patrick M. O'Neill, Tammy Gries, Hannah M. Tetreault, Thomas E. Clemente

Department of Plant Pathology: Faculty Publications

To increase phenylpropanoid constituents and energy content in the versatile C4 grass sorghum (Sorghum bicolor [L.] Moench), sorghum genes for protiens related to monolignol biosynthesis were overexpressed: SbMyb60 (transcriptional activator), SbPAL (phenylalanine ammonia ase), Bmr2 (4-coumarate: CoA ligase), and SbC3H (coumaroyl shikimate 3-hydroxylase). Overexpression lines were evaluted for responses to stalk pahtogens under greenhouse and field conditions. Greenhouse-grown plants were inoculated with Fusarium thapsinum (Fusarium stalk rot) and Macrophomia phaseolina (charocal rot), which cause yield-reducing diseases. F. thapsinum-inoculated overexpression plants had mean lesion lengths not significantly different than wild-type, except for significantly smaller lesions on two of three SbMyb60 and …

Combating Drug Resistance - Comparison Of The Antibiotic Effect Of Hydrastis Canadensis Extract And Pure Berberine Via Minimum Inhibitory Concentration Assay, William Luke Scott, Timothy D. Trott

Research in Biology

Herbal medicines are a melee of complex organic chemicals, making it difficult to ascertain their direct mechanism of action. In contrast to mainstream pharmaceuticals, it is argued that herbal medicines are effective because of multiple constituents working synergistically. The complexity of herbal medicines may give them advantages over simpler pharmaceuticals in combating antibiotic resistant microbes, but these advantages can be difficult to quantitate. Popular literature frequently espouses the healing properties of herbal medicines, but many of these claims are not scientifically supported. Many gains could be realized in public health and medicine if more research was aimed at validating / …

The Tripartite Interaction Between Arbuscular Mycorrhizal Fungi, Rice, And Insects, Lina Bernaola Alvarado

LSU Doctoral Dissertations

Losses caused by pests remain an important limitation to achieving high rice yields in the United States. Arbuscular mycorrhizal fungi (AM fungi) are able to modify plant physiology by increasing plant growth or inducing defense responses against insect herbivores. However, studies of the role of AM fungi in agroecological factors, including natural occurrence, plant resistance, soil dependency, and plant tolerance, with specific regards to pests that feed on rice plants have not been conducted before. A three-year study revealed natural occurring colonization by AM fungi on rice roots sampled in four rice-producing areas in the southern United States. Overall, rice-AM …

Understanding Host-Fungus Interactions Between Soybean And Phakopsora Pachyrhizi To Enhance Soybean Resistance To Rust Disease, Dongfang Hu

LSU Doctoral Dissertations

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi was first reported in Japan in 1902. In 2004, Asian soybean rust was first reported in Louisiana and other Southeastern US states. It is one of the most important soybean diseases worldwide. Even though fungicide application can offer some protection and prevent severe yield losses caused by ASR if applied promptly, it is not a viable option as a long-term disease control measure because it increases the growers’ operation costs and the risk of environmental pollution. In addition, it also increases the chances of developing fungicide resistance within a pathogen population. The …

Development Of Sheath Blight-Resistant Breeding Lines For Southern U.S. Environments And Morphological And Genetic Survey Of Giant Salvinia Populations In Louisiana And Texas, Dominique Clark Galam

LSU Doctoral Dissertations

The southern US environment is a very conducive environment for agriculture and fisheries. Rice farming, shrimping and water related activities help drive the local economy. However, there are several factors that impede the success of these activities. Sheath blight (SB) disease caused by Rhizoctonia solani is one of the major biotic constraints to high grain yield and quality for most commercial U.S. rice varieties. Although different breeding lines with high levels of "partial resistance" have been developed none has been used directly as a commercial variety. The first research objective of this research was to identify and develop advanced breeding …

Mitotic Recombination And Rapid Genome Evolution In The Invasive Forest Pathogen Phytophthora Ramorum, Angela L. Dale, Nicolas Feau, Sydney E. Everhart, Braham Dhillon, Barbara Wong, Julie Sheppard, Guillaume J. Bilodeau, Avneet Brar, Javier F. Tabima, Danyu Shen, Clive M. Brasier, Brett M. Tyler, Niklaus J. Grünwald, Richard C. Hamelin

Department of Plant Pathology: Faculty Publications

Invasive alien species often have reduced genetic diversity and must adapt to new environments. Given the success of many invasions, this is sometimes called the genetic paradox of invasion. Phytophthora ramorum is invasive, limited to asexual reproduction within four lineages, and presumed clonal. It is responsible for sudden oak death in the United States, sudden larch death in Europe, and ramorum blight in North America and Europe. We sequenced the genomes of 107 isolates to determine how this pathogen can overcome the invasion paradox. Mitotic recombination (MR) associated with transposons and low gene density has generated runs of homozygosity (ROH) …

Proceedings Of The 46th Annual Meeting Of The Southern Soybean Disease Workers (March 6-7, 2019, Pensacola Beach, Florida), Carl Bradley, Heather M. Kelly, Burt Bluhm, Danise Beadle, Patricia Bollich, Trey Price, Tom Allen

Southern Soybean Disease Workers: Conference Proceedings

Contents

List of SSDW Officers

Agenda for March 6-7, 2019

Abstracts for presented/contributed papers

Evaluating phytotoxicity in response to fungicide by adjuvant combinations. TW Allen and TH Wilkerson

Effect of delayed harvest on the seed quality of commercial soybean cultivars. JC Rupe, JA Rojas, R Holland, SR Segalin, RD Bond, and JA Still

Virome of Macrophomina phaseolina isolates collected from soybean fields in Mississippi. Nina Aboughanem-Sabanadzovic, Tessie Wilkerson, Tom Allen, and Sead Sabanadzovic

Genomic evidence for interspecific hybridization in Cercospora cf. flagellaris strains associated with Cercospora leaf blight of soybean. Alex Zaccaron, Kona Swift, Ahmad Fakhoury, and Burt Bluhm

Identification …

Global Responses Of Resistant And Susceptible Sorghum (Sorghum Bicolor) To Sugarcane Aphid (Melanaphis Sacchari), Hannah M. Tetreault, Sajjan Grover, Erin Scully, Tammy Gries, Nathan A. Palmer, Gautam Sarath, Joe Louis, Scott E. Sattler

Department of Entomology: Faculty Publications

The sugarcane aphid (Melanaphis sacchari) has emerged as a significant pest for sorghum. The use of sugarcane aphid-resistant sorghum germplasm with integrated pest management strategies appears to be an excellent solution to this problem. In this study, a resistant line (RTx2783) and a susceptible line (A/BCK60) were used to characterize the differences in plant responses to the sugarcane aphid through a series of experiments, which examined global sorghum gene expression, aphid feeding behavior and inheritance of aphid resistance. The global transcriptomic responses to sugarcane aphids in resistant and susceptible plants were identified using RNA-seq and compared to the …

Good To The Last Drop: The Emergence Of Coffee Ringspot Virus, Michael Goodin, Antonia Dos Reis Figueira

Plant Pathology Faculty Publications

Two and a half billion times per day a human hand reaches for a fresh cup of coffee. Although arguably dispensable for life per se, with an industry value of US$174 billion, coffee provides the lifeblood that sustains economies of producing countries located in the “coffee belt” situated between the Tropics of Cancer and Capricorn. As a “solvent” in which many human interactions take place, coffee is witness to the broad spectrum of human activities from the mundane to the pleasurable and personal. However, in opposition to its economic, cultural, and physiological importance, diseases such as coffee rust (caused by …

Investigations Into Aspergillus Flavus Infection Of Corn And Regulation Of Aflatoxin Production By Volatiles And Biocontrol Strains, Rebecca R. Sweany

LSU Doctoral Dissertations

Aspergillus flavus is an ascomycete fungus impacting agriculture, public and environmental health due to production of acutely-toxic, carcinogenic aflatoxins in oil seed crops, especially corn in Louisiana, and lung infections of immunocompromised patients resulting in a leading cause of AIDS patients’ deaths globally. The most effective aflatoxin mitigation strategy, biocontrol by atoxigenic A. flavus presents several concerns including: dissemination of a human pathogen, possible sexual reproduction and reliance on precise environmental conditions. Several aspects of A. flavus biology were investigated to potentially improve treatments. Studies investigated how genotypically diverse members within the A. flavus population interact with other population members …