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Effects Of Riverine Barriers On Avian Evolution In The Amazon Basin, Andre Eugene Moncrieff

LSU Doctoral Dissertations

The high biodiversity found in the Amazon Basin has long captivated the attention of naturalists and evolutionary biologists seeking to explain its origins. Early observations by Alfred Wallace highlighted the role of rivers in delimiting the geographic ranges of many species; furthermore, where rivers narrow towards their headwaters, he noted that some species cross rivers freely. A major goal of this dissertation is to investigate how these and other observations about riverine barriers might inform our understanding of how speciation unfolds in Amazonia. My approach involved generating genomic data with dense geographic sampling for manakins in the genus Lepidothrix, …

Development Of Functional Markers For Resistance To Smut And Identification Of Genes Differentially Expressed In Response To Brown Rust In Sugarcane, Jose David Cortes

LSU Doctoral Dissertations

Smut, caused by Sporisorium scitamineum and brown rust, caused by Puccinia melanocephala, are two of the most important diseases that affect sugarcane production in Louisiana and worldwide. Smut continues to cause losses in the breeding program in Louisiana. Therefore, a QTL analysis was conducted to identify molecular markers associated with resistance in F₁ progeny (162) of a biparental cross between susceptible cultivar L 99-233 and resistant HoCP 96-540. Using 1,574 single-dose SNP markers, a total of 253 linkage groups (LG) were obtained with a genome coverage of 24,580.15 cM. Six QTLs were localized on five LGs. The highest …

The Effects Of Tillage And Cover Crops On Crop Yield And Soil Properties In Wheat Double-Cropping Systems, Peters E. Egbedi

LSU Doctoral Dissertations

This three-year study was conducted on a commerce silt loam soil at the Northeast Research and Experiment Station near St. Joseph, Louisiana to evaluate the following objectives: 1) evaluate crop yield response to tillage, winter, and summer cover crops in wheat double-cropping systems. 2) evaluate the effects of tillage, winter and summer cover crops on soil properties under different cropping systems. 3) quantify the economic benefits of double-cropping, cover cropping and monoculture systems under conventional and no tillage practices. A winter cover crop (WCC) mix (winter wheat (Triticum aestivum and Austrian winter pea (Pisum sativum) and summer …

Spatiotemporal Transcriptome Diversity And Responses To Salinity Tolerance In The Extremophyte Schrenkiella Parvula, Chathura Wijesinghege

LSU Doctoral Dissertations

Schrenkiella parvula is an extremophyte model related to the most widely studied plant model, Arabidopsis thaliana and Brassica crops in the mustard family (Brassicaceae). It can thrive in highly saline environments where the soil is enriched in Na⁺, K⁺, Li⁺, borates, and chlorides. Understanding how this extremophyte can survive high salinity with genomic adaptations can provide insight into developing stress resilient crops in the future. Gene expression of S. parvula in response to salt has been investigated using shoot and root tissue from mature vegetative-phase plants. However, prior studies have not examined the transcript …

The Applied Use Of Zein Nanoparticles In Agriculture, Colin Bonser

LSU Doctoral Dissertations

Nanotechnology is a multifaceted and a promising strategy in agricultural pest management for the development of insecticides or insecticide carriers. Research has shown that nanoparticles increase stability and efficacy of entrapped chemical pesticides to prevent active ingredient degradation while improving chemical stability and solubility. The following work evaluated nanoparticles synthesized from biopolymers, materials that originate from renewable sources also have an increased biodegradability.
Work was conducted under laboratory, greenhouse, and field conditions to test the biopoloymers as possible insecticide and insecticide carriers. The primary biopolymer evaluated in the following studies was zein, although lignin and chitosan were also evaluated. Overall, …

Esterase Mediated Insecticide Resistance In The Southern House Mosquito, Culex Quinquefasciatus, Vivek Pokhrel

LSU Doctoral Dissertations

Much is known about the development of insecticide resistance associated with targeted application against insect populations. However, off-target selection by applications of insecticides in agricultural and residential sites also impacts development of insecticide resistance and is understudied. Similarly, the impact of selecting one life stage of mosquitoes on the insecticide susceptibility of different life stages is largely unknown. The first part of this study shows that susceptibility to chlorantraniliprole, which is applied in rice and sugarcane fields in LA, decreased (5.7 to12-fold) in populations of Culex quinquefasciatus collected from near these fields compared to a reference field strain. In addition, …

Fish And Invertebrate Community And Trophic Structure In The Gulf Of Mexico Coastal Plains Watersheds Across Varying Hydrologic Connectivity., Erin Elizabeth Thayer

LSU Doctoral Dissertations

Subtropical Northern Gulf of Mexico coastal plains watersheds tend to have mild seasonal temperature, low topography, and fine, mostly homogenous substrate sizes; these watersheds may not follow fish and invertebrate community patterns predicted by established lotic paradigms because those paradigms tend to describe communities in either temperate or tropical regions. However, the bases of most generally accepted lotic paradigms involve evaluation of allochthonous and autochthonous contributions to lotic ecosystems via three hydrologic connectivity dimensions including vertical (hyporheic and shallow groundwater), lateral (floodplain), and longitudinal (upstream and downstream). My dissertation goals were to explore these three dimensions within Louisiana coastal plains …

Identification Of Quantitative Trait Loci (Qtls) For Resistance To Bacterial Leaf Streak: Xanthomonas Translucens Using Qtl And Association Mapping In Three Populations Of Soft Red Winter Wheat, Benjamin Tyler Meritt

LSU Doctoral Dissertations

Bacterial leaf streak (BLS) and black chaff, caused by Xanthomonas translucens pv. undulosa (Xtu), can be a very destructive disease of wheat, especially in the warmer, wetter areas of the Southeastern U.S. Yield losses of up to 40 percent have been recorded in some cases in southern wheat growing regions. With no effective agronomic or chemical method of disease control, identification of genetic resistance is seen as a promising solution. Three soft red winter wheat populations (GAWN, ARK-SNP, and AGS 2060- AGS 2035 DH) representative of soft red winter wheat germplasm in the southeastern U.S. developed by …

The Risks Posed By Mosquito Ultra-Low Volume Applications To Procambarus Clarkii Production, Timothy Mcnamara

LSU Doctoral Dissertations

Mosquito abatement has received much scrutiny due to concerns about the impacts of control applications on non-target organisms. In Louisiana, a great deal of this concern has come from crawfish farmers claiming mosquito abatement applications have damaged crawfish production. To determine which mosquito abatement practices and products pose a risk to crawfish production, we conducted a series of studies examining mosquito abatement practices in the vicinity of crawfish production fields and the impacts of common mosquito abatement product exposure on crawfish health and production. We found that mosquito ULV applications are the most likely to result in exposure to crawfish …

Effects Of Sensory Cues On Product Acceptability And Consumer Perceptions, Emotions, And Behavior, Cristhiam Gurdian Curran

LSU Doctoral Dissertations

Visual and cognitive cues can affect overall liking (OL) and consumer perceptions, emotions, and behavior. The first study explored the effect of product color difference on the liking, perception, and purchase intent (PI) of cheese-flavored-tortilla chips (CFTC) formulations (A and B) on serving plates (plastic, foam, and paper). Color differences between formulations influenced crunchiness and saltiness liking and perception, which together with overall flavor liking and formulation, mainly determined CFTC OL. Although having similar fracturability (N) and sodium content, formulation A had higher crunchiness and saltiness likings. PI was influenced by crunchiness, saltiness, and OF liking with 37, 49, and …

Comparative Genomics And Virulence Studies Of Streptomyces Soil Rot And Scab Pathogen Species, Natasha Soares

LSU Doctoral Dissertations

Comparative genomic analyses were performed to gain insights into the organization and content of the genome of Streptomyces ipomoeae, the soil rot pathogen that infects sweetpotatoes. Unlike Streptomyces scab pathogens, the thaxtomin phytotoxin gene cluster (txt) in S. ipomoeae does not appear to reside within a genomic island and has diverged from its scab pathogen counterparts. Increased usage of the rare TTA codon, particularly for the txt cluster, suggests greater translational control by the bldA tRNA in S. ipomoeae. Orthologous gene searches and secondary metabolite profiling yielded ortholog groups and metabolite gene clusters that were exclusive …

The Effects Of Drought And Shade On Bottomland Hardwood Regeneration, Charles Joseph Pell

LSU Doctoral Dissertations

Floodplain forests support a high diversity of tree species adapted to regenerate under fluctuating water and light availability. Regeneration regulates species composition, and shade and flood tolerance influence the likelihood of regeneration. Regeneration failure of shade-intolerant and flood-tolerant tree species commonly occurs in southcentral and southeastern floodplain forests of the United States, also known as bottomland hardwoods (BLHs). In many BLHs reduced flooding has resulted in a dryer floodplain. These changes in flooding are linked to recent shifts in species composition. The mechanisms controlling regeneration in BLHs and these composition shifts are poorly understood. In a controlled germination experiment, I …

Integration Of Remote Sensing Approaches For In-Season Nitrogen Management, Murilo De Santana Martins

LSU Doctoral Dissertations

Nitrogen (N) management is being conducted at flat rate in Louisiana due to practicality and convenience, but the price of N fertilizer and high breakeven costs are forcing producers to find ways to reduce costs and optimize N application. In this scenario, precision agriculture technologies, specifically the use of optical sensors on board of unmanned aerial systems (UAS) to variable rate N application on farm is showing a promising approach to save inputs and reduce environmental impacts. However, the general goal of this research was to develop and evaluate in-season N management approaches for N recommendation in corn (Zea …

Genetic Dissection And Qtl Pyramiding To Enhance Salinity Tolerance In Rice (Oryza Sativa L.), Sandeep Chapagain

LSU Doctoral Dissertations

Salinity is emerging as a major threat to rice production worldwide due to climate change and anthropogenic sources. We performed three different population development approaches using exotic salt tolerant donors in US rice backgrounds to identify the salt tolerant QTLs/genes and tolerant breeding lines. First approach involved development of a biparental introgression lines (ILs) population by utilizing a salinity tolerant donor ‘TCCP’ in an elite rice cultivar ‘Cheniere’ background and mapping of QTLs at germination, seedling, and reproductive stages A total of seven QTLs for five germination traits, 16 QTLs for seven seedling stage traits, and 30 QTLs for ten …

Evolution Of Freshwater Fishes In The Northern Neotropics, Diego Elias

LSU Doctoral Dissertations

The northern Neotropics (NN) represents one of the most geologically-complex regions on the planet, composed of island-like geological blocks that have undergone multiple episodes of isolation and connectivity at various geological times. The riverscapes of the NN harbor a unique assemblage of freshwater fishes. In contrast to the freshwaters systems of South America, which are dominated by ostariophysan lineages, the aquatic systems of the NN are dominated by lineages of two families: Cichlidae (cichlids) and Poeciliidae (livebearers). It has been suggested that the geologically complex nature of the region allowed ancestors of cichlids and livebearers to colonize and radiate within …

Insights Into The Speciation Process From Genomic And Phenotypic Analysis Of An Avian Hybrid Zone In Amazonia, Glaucia Christina Del-Rio

LSU Doctoral Dissertations

Understanding the outcome of secondary contact is essential to shed light on the mechanisms governing species formation and maintenance. In Amazonia, closely related bird taxa with limited dispersal abilities are often separated by rivers, which presumably act as dispersal barriers. However, at the headwaters, rivers cease to be dispersal barriers, and this generates opportunities for secondary contact. In my dissertation, I studied genomic mechanisms associated with phenotypic differences, mitochondrial DNA structure, and putative reproductive barriers between two hybridizing Amazonian bird species in the genus Rhegmatorhina, a group of antbirds that find their arthropod prey exclusively by following army-ant swarms. …

The Importance Of Co2 Recapture In The Co2 Concentrating Mechanism Of Chlamydomonas Reinhardtii, Ashwani Rai

LSU Doctoral Dissertations

The aim of this thesis is to investigate the CO₂ concentrating mechanism (CCM) of Chlamydomonas reinhardtii and to develop a quick method for estimating the activity of carbonic anhydrases (CAs). The first project demonstrates that there are two almost identical mitochondrial CAs in C. reinhardtii, CAH4 and CAH5, that help to maintain photosynthesis and minimize the leak of CO₂ generated by respiration and photorespiration. We used an RNAi approach to reduce the expression of CAH4 and CAH5 so that their physiological functions could be studied. RNAi mutants with low expression of CAH4 and CAH5 have impaired rates …

Chloride Channels That Mediate A Transient Nitric Oxide-Dependent Synaptic Polarity Switch In Retinal Amacrine Cells., Tyler Christopher Rodriguez

LSU Doctoral Dissertations

Cytosolic chloride (Cl^-) concentration determines whether GABAergic and glycinergic synapses are inhibitory or excitatory. Ionotropic GABA and glycine receptors passively conduct Cl­^- leading to membrane depolarization or hyperpolarization depending on the Cl^- equilibrium potential. Accordingly, the distribution of Cl^- across the plasma membrane has the potential to determine the properties of networks of retinal amacrine cells (ACs) and their postsynaptic partners. Ion channels are responsible for establishing Cl^- reversal potential. Nitric oxide (NO) is a signaling molecule that can be generated in the inner retina where ACs form synapses. We have shown that NO …

Breeding Ecology Of Mottled Ducks In Southwestern Louisiana, Elizabeth Sophia Bonczek

LSU Doctoral Dissertations

Mottled ducks are a resident species found in the southern United States that rely on coastal marsh and associated habitat to fulfill the needs of the entirety of their annual cycle. Population monitoring has revealed declines in western Gulf Coast (WGC) mottled ducks since 2008. Mottled duck populations are influenced by survival and recruitment, and changes in these factors may contribute to population declines. The overarching goal of this project was to identify the mechanisms potentially limiting WGC mottled ducks.

I captured adult female mottled ducks during molt on Rockefeller Wildlife Refuge and adjacent lands in southwestern Louisiana from 2017–2019. …

Geographical Distribution, Allele Frequency, And Inheritance Of Cry1a.105 And Cry2ab2 Resistance In Helicoverpa Zea In The Southeastern Region Of The United States, Wenbo Yu

LSU Doctoral Dissertations

The corn earworm, Helicoverpa zea (Boddie), is a target pest of Bacillus thuringiensis (Bt) maize and cotton in the U.S. Previous studies have reported that this pest has developed field resistance to pyramided Cry1A/Cry2A maize and cotton in certain areas of the southern United States. The objectives of this study were to 1) determine the current status and distribution of the resistance to Cry1A.105 and Cry2Ab2 in H. zea in the southeastern United States; 2) estimate the resistance allele frequencies to the two Bt proteins in H. zea field populations in the region, and 3) assess the inheritance of the …

Sodium Mediates Developmentally Plastic Responses In Plants And Herbivores, Luis Santiago-Rosario

LSU Doctoral Dissertations

Sodium plays a crucial role in organismal performance, trophic-level interactions, and eco-evolutionary dynamics. For plants, sodium impacts osmoregulation, growth, and water uptake. For animals, sodium is essential influencing osmoregulatory processes, muscle and neural development, and blood regulation. My dissertation aims to disentangle why sodium mismatch affects resource-consumer interactions and its influence on morphological and behavioral plasticity. First, I identified how sodium impacts plant performance and sodium accumulation strategies. I initially focused my research on understanding how increasing substrate sodium affects plant growth and tissue sodium accumulation strategies in controlled settings using a systematic review approach. I found that saltier plants …

Experts’ Views On Issues Affecting Egg Labeling In The United States: A Delphi Study, Rexanna Powers

LSU Doctoral Dissertations

When purchasing food, many consumers have reported they question the ethical and humane treatment of products derived from animals at the point of purchase. To complicate this issue further, many U.S. consumers lack exposure, interaction, and involvement with the agricultural industry. As a result, they have reported a willingness to pay premium prices for meats, dairy, and eggs whose packaging suggests quality welfare practices. Therefore, the purpose of this investigation was three-fold: (1) establish operational definitions for poorly understood poultry industry terms, i.e., cage-free, free-range, pasture-raised, and organic; (2) describe experts’ perceptions of the strengths, weaknesses, opportunities, and threats (SWOT) …

Synthesis Of Thiol-Acrylate Hydrogels For 3d Cell Culture And Microfluidic Applications, Anowar Hossain Khan

LSU Doctoral Dissertations

Globally cell culture is an $18.98 billion industry as of 2020, with an 11.6 percent annual growth rate. Drug discovery has an estimated worth of $69.8 billion in 2020 and is predicted to grow to $110.4 billion by 2025. Three-dimensional (3D) cell culture of cancer cells is one of the rapidly growing felids since it better recapitulates in vivo conditions compared to two-dimensional (2D) models. However, it is challenging to grow 3D tumor spheroids outside the body, and some of the existing technology can generate these spheroids outside the human body but poorly mimic in vivo tumor models. Therefore, there …

Visuomotor Rotation Adaptation And Workspace Manipulation: A Behavioral And Cognitive Emphasis, Reuben N. Addison

LSU Doctoral Dissertations

This is a three-study dissertation in which we aimed to broaden our knowledge of the mechanisms contributing to a 45° clockwise visuomotor adaptation by including variations in workspace. We provide behavioral and in one study physiological outcomes as evidence to support our conclusions. In the first experiment, we observed the adaptation of movement parameters such as pathlength, movement time, resultant velocity, and normalized jerk across groups trained with rotated visual feedback with both the left and right hands. Workspace location and hand differentially affected movement trajectory length. The group that practiced the task with their nondominant, left hand showed larger …

The Design, Construction, And Testing Of A Recombinant Dna Vaccine For Brucella Abortus And Brucella Melitensis, Stephanie Lynn Korle

LSU Doctoral Dissertations

Brucella spp. are a bacterium that cause brucellosis, a zoonotic disease, which is commonly seen in cattle, sheep, goats, swine, and canines. Brucellosis is a problem worldwide, although it is eradicated in some countries (Garin-Bastuji et al. 1998). The reason for designing recombinant DNA (rDNA) vaccines opposed to utilizing the live-attenuated vaccines on the market is that they cannot be given to pregnant animals without potentially causing abortion, while an rDNA vaccine should be safe for pregnant animals since it does not contain viable bacteria. Also, there are no serological tests that can accurately distinguish between an animal vaccinated …

Weed Management With Pro-Herbicides Benzobicylon And Florpyrauxifen-Benzyl In Louisiana Rice Production, William Bradley Greer

LSU Doctoral Dissertations

Field studies were conducted in 2020 and 2021 to evaluate benzobicyclon tolerance to 71 weedy rice accessions collected from Louisiana and southern Arkansas. Benzobicyclon was applied at 373 g ai ha^-1 as a postflood application on 3- to 4-leaf rice. At 28 DAT, less than 15% control was observed on 70% of the accessions and 80% or better control was observed on 3% of accessions. Inconsistent weedy rice control can be attributed to the presence or absence of a functional HIS1 allele. The functional HIS1 allele was present in 96% of accessions when treated with benzobicyclon control was less …

Impact Of New Technologies On Weed Control In Louisiana Rice Production, David C. Walker

LSU Doctoral Dissertations

Field studies were conducted in 2018-2021 at the LSU Agricultural Center’s H.R. Caffey Rice Research Station (RRS) near Crowley, LA, and the Dean Lee Research and Extension Center (DLREC) near Alexandria, LA to evaluate off-target florpyrauxifen movement on soybean. Soybean was treated with florpyrauxifen at the V4-V5 or R1-R2 growth stages. Soybean injury was evaluated at 1, 7, 14, and 28 days after treatment (DAT) and soybean plant height (cm) was recorded at 7, 14, and 28 DAT. At soybean maturity, yield and individual yield components were subjected to regression analysis to describe the relationship between florpyrauxifen rate and soybean …

Multi-Year Data Analysis And Genomic Selection To Improve The Efficiency Of A Rice Breeding Program, Tommaso Cerioli

LSU Doctoral Dissertations

Plant breeding dramatically improved crops performances during human history and will play a pivotal role in shaping the future of agriculture. However, this activity requires large amount of time and resources. The availability of multi-year datasets and abundant DNA information enables new analyses and breeding approaches that can increase the productivity and efficiency of a breeding program. In recent years, the LSU Rice Breeding Program has implemented marker assisted selection (MAS) and genomic selection (GS) to predict performance of rice genotypes before field testing. The goal of this project was to conduct analyses and test molecular approaches to increase the …

The Herpes Simplex Virus Type-1 (Hsv-1), Vc2 Live-Attenuated Vaccine Strain Induces Robust Antitumor Immune Responses And Ameliorates Intra-Tumor Immunosuppression In An Immunocompetent B16f10-Derived Murine Melanoma Model, Ifeanyi Kingsley Uche

LSU Doctoral Dissertations

Current cancer immunotherapies include immune checkpoint inhibitors, adoptive cellular therapy, and cancer vaccines. While some of these therapies have met with great clinical success, they are associated with several limitations. Oncolytic virotherapy (OVT) has emerged as a bonafide promising immunotherapy, that uses viral infection to liberate tumor antigens in an immunogenic context to promote the development of anti-tumor immune responses. At present, Talimogene laherparepvec (T-VEC; Imlygic™), a modified type 1 herpes simplex virus (HSV-1) is the only FDA approved OVT for human cancer treatment (melanoma). While T-VEC is associated with limited response rates, its modest efficacy supports the continued development …

Inhibition Of Biotin Carboxylase By Three Antibacterial Compounds, Matt Craft

LSU Doctoral Dissertations

The rise of antibacterial resistant bacteria is a major problem in the United States of America and around the world. Millions of patients are infected with antimicrobial resistant bacteria each year. Novel antibacterial agents are needed to combat the growing and present crisis. Acetyl-CoA carboxylase (ACC), the multi-subunit complex which catalyses the first committed step in fatty acid synthesis, is a validated target for antibacterial agents. However, there are at present, no commercially available antibiotics that target ACC. Ethyl 4-[[2-chloro-5-(phenylcarbamoyl)phenyl]sulfonylamino]benzoate (SABA1) is a compound that has been shown to have antibacterial properties against Pseudomonas aeruginosa and Escherichia coli. SABA1 inhibits …