Plant Breeding and Genetics Commons^™

Towards Improved Stress Resilience, Optimal Growth And Enhanced Biosafety In Transgenic Plants, Xiaotong Chen

All Dissertations

This dissertation investigates biotechnology strategies to improve plant stress resilience, growth, and biosafety in transgenic perennial grasses using creeping bentgrass as a model system. Functional analyses of non-coding RNAs such as miR164 and miR169 showed that regulatory non-coding RNAs influence plant architecture and abiotic stress responses through broad developmental and transcriptional networks, supporting them as valuable engineering targets for complex trait improvement. The dissertation also developed a dual recombinase platform for transgene containment and removal, linking trait engineering with biosafety control. Additionally, the recombinases themselves were examined for their potential impact on heterologous host and were found to reshape plant …

Sorghum Grain Secondary Metabolites And Underlying Genetics To Reduce Foodborne Pathogens In Poultry, Maria A. Conti

All Dissertations

The rise in antibiotic-resistant pathogens poses a threat to the poultry industry's ability to maintain animal health, prompting growing interest in alternatives to synthetic antibiotics. The use of non-tannin sorghum [Sorghum bicolor (L.) Moench] in poultry rations offers a valuable alternative, as this cereal grain has a high bioactive profile that can provide health benefits, including antimicrobial (AM) activity. The scope of this study was to examine the AM potential of non-tannin sorghum grain against Clostridium perfringens, a major foodborne pathogen that negatively impacts poultry health and production. To that end, the inhibitory effects of a non-tannin sorghum …

Discovering The Genetics Underlying Speciation Traits In Heuchera (Coral Bells), Tajinder Singh

Honors Theses

Hybridization is a key evolutionary mechanism for generating biological diversity, ultimately shaping diversification and adaptation of plant lineages in natural and agroecosystems.  Our understanding of the frequency, distribution, and significance of hybridization is rapidly increasing, but the external driving forces that dictate why certain species hybridize, and others do not remain obscure. The physical traits that shape gene flow and trait sharing among species are likely to be among the key factors that directly control hybridization. Gene flow in most plants is mediated by pollinating insects and thus by pollination syndromes, which are suites of floral traits that have evolved …

Genome Wide Association Study (Gwas) On Different Economic Traits And Epigenetic Stability Of Sweetpotato In Louisiana, Ajay Dhungana

LSU Doctoral Dissertations

Sweetpotato [Ipomoea batatas (L.) Lam] is a globally important food, feed, and industrial crop, yet its improvement is constrained by a complex hexaploid genome, clonal propagation, and susceptibility to multiple diseases. In Louisiana, production is threatened primarily by Fusarium oxysporum f. sp. batatas (Fusarium wilt) and Ceratocystis fimbriata (Black rot). Furthermore, the in vitro propagation methods essential for disease-free planting material and germplasm conservation can introduce epigenetic instability that undermines clonal fidelity. This dissertation integrates genome-wide association studies (GWAS), genotype by environment interaction (GEI) and DNA methylation profiling to dissect resistance mechanisms and assess epigenetic stability in Louisiana sweetpotato …

Characterization Of The Genetic Diversity Of Curlyleaf Pondweed (Potamogeton Crispus L.) In The Contiguous United States And Canada And Analysis Of Possible Hybrid Potamogeton Crispus Lineages, Mallory M. Kaiser

All Graduate Theses, Dissertations, and Other Capstone Projects

Curlyleaf Pondweed (Potamogeton crispus L.) is a prolific invasive species that has spread across the United States and into parts of Canada since its introduction to North America in the 1840s. It causes extensive economic and environmental damage across its invasive range, and its control and eradication are of utmost importance to agricultural, ecological, recreational, and transportational stakeholders. Developments in molecular ecology and invasive management have found that genetic diversity and hybridization of aquatic macrophytes may affect their susceptibility to herbicide treatments, and genotype or lineage identification are important control variables that must be considered in field and …

Breeding For Fhb Resistance And Post-Harvest Quality In Soft Red Winter Wheat, Margaret E. Gillum

Theses and Dissertations--Plant and Soil Sciences

Soft red winter wheat (Triticum aestivum L.) is both an economically and nutritionally important crop in the global food supply. Despite its global importance, wheat is continually threatened by fungal diseases. Fusarium head blight (FHB), caused by Fusarium graminearum, is a devastating fungal disease affecting wheat worldwide, resulting in low yields, reduced test weight and mycotoxin production. The mycotoxin deoxynivalenol (DON) is toxic to humans, results in feed rejection in livestock, and is heavily monitored in the food supply. Because of wheat’s importance in the food system, post-harvest quality (milling, baking, and flavor) has been a growing area of …

Sex In Plants: Birth, Death, And Trying To Survive In Changing Climates, Elena M. Meyer

Theses and Dissertations

Plant mating systems are key determinants of fitness. Angiosperms exhibit a wide variety of reproductive strategies, including self-fertilization (or selfing), outcrossing, and mixed mating. It has been estimated that up to 43% of plant species are capable of selfing, and selfing has been hypothesized to provide reproductive assurance where opportunities for mating may be limited, such as in marginal environments. However, questions regarding the overall distribution of selfing rates across angiosperms, the maintenance of mixed mating in the face of inbreeding depression, and the impact of self-fertilization on diversification rates remain incompletely resolved. Here, we explore the dynamics of self-fertilization …

Citrullus Amarus Drought Tolerance: An Above And Below Ground Analysis, Ben A. Hyland

All Theses

Ever rising environmental temperatures threaten global food security by worsening severity and increasing the occurrence of drought. Commercially cultivated watermelon (Citrullus lanatus), have reduced drought tolerance due to a narrow genetic base caused by breeding for desirable traits such as sweetness, size, and flesh/rind color. Comparatively, the crop wild relative desert watermelon variety (Citrullus amarus), while more drought tolerant than their commercially cultivated relatives (C. lanatus), still require large amounts of water to grow and produce reliable fruit yields. Watermelon root morphology plays a key role in their ability to tolerate drought, with more …

Breeding For Disease Resistance In Melon And Watermelon, Venkata Rao Ganaparthi

All Dissertations

Watermelon and cantaloupe are two widely consumed cucurbits, but their acreage in the United States reduced by nearly 50% in last two decades. Fusarium wilt caused by a soil borne pathogen Fusarium oxysporum f. sp. niveum(Fon) race 2 is a major limiting factor in watermelon production as it reduces yields by 80%. Grafting watermelon plants onto the root stock of wild, disease-resistant varieties like ‘Carolina Strongback’ is the best strategy to manage Fon race 2. Though effective, this approach increases production costs.

Part of this dissertation focused on finding more sustainable, cost-effective solutions to control Fusarium wilt …

Determining The Origin Of An Isolated Great Lakes Plant Species, Agoseris Glauca (Asteraceae), Seth Paul Hiers

Masters Theses

Small, isolated populations often have low genetic diversity and low potential for adaptation in response to environmental changes. Alternatively, isolated communities are often more likely to display local adaptations and over time speciate. The Great Lakes Region is home to over 50 vascular plant species that are disjunct from the species’ core populations. Agoseris glauca (Asteraceae) is a Great Lakes disjunct and Michigan state threatened species geographically isolated from its core range by 900 km. This study uses Genotyping by Sequencing to assess the population genetics of A. glauca for two Michigan disjunct populations and five western populations in the …

Breeding Biofortified Protein Rich Organic Pulses For Better Human Health, Sonia Salaria

All Dissertations

Pulse crops are dry grains of legumes, the second most consumed plant crops in the world after cereals. These crops are one of the primary sources of plant-based protein and contain high concentrations of pre-biotic carbohydrates, minerals and vitamins. Recognizing the health benefits of pulses intake, their demands as sustainable food and changes in people’s diet preferences for plant-based protein have increased awareness for pulses consumption. With this scenario, improving the nutritional profile of pulse crops for rich nutrition has been an opportunity for breeders to explore and tailor the available germplasm to develop nutrient dense pulses. Furthermore, the genomic …

Assessment Of A Muscadine Grape (Vitis Rotundifolia) Mapping Population For Tolerance To Pierce’S Disease Pathogen Xylella Fastidiosa And Resistance To Black Rot Disease Pathogen Guignardia Bidwellii, Anushka Tennakoon

Master's Theses

Pierce’s disease (PD) and black rot disease cause severe economic losses for grape production under humid and warm conditions. Identifying resistance genes is crucial for controlling these disease by developing resistant cultivars. Muscadine grape (Vitis rotundifolia) cultivar ‘Pam’ has been identified to possess a high level of resistance to diseases. To elucidate the genetic basis of the resistance to the causal pathogens Xylella fastidiosa and Guignardia bidwellii in this cultivar, parents and 141 F1 individuals developed from open pollinated ‘Pam’ were evaluated for two seasons under natural disease pressure. The mapping population was genotyped using genotyping-by-sequencing (GBS) and …

Novel Tools And Datamining Techniques To Visualize And Interpret Historical Sugarcane Datasets, Zachary A. Taylor

LSU Master's Theses

Heritable genetic variation is an essential raw ingredient of variety development programs. This variation is acted upon via selection by identifying elite progeny that can be utilized agronomically or exploited as parents. Sugarcane breeders are tasked with creating optimal genetic variation through crossing. Prior knowledge of pedigree and parental performance allows breeders to discern which crosses to prioritize, since the time to make crossing decisions and the space to evaluate tens and thousands of progenies are both limited resources in sugarcane variety development programs. In this project, we have updated and validated the U.S. sugarcane pedigree …

Improved Management Strategies For Botrytis Fruit Rot, Macrophomina Root Rot, And Verticillium Wilt In California Strawberry Production, Joseph A. Ramirez

Master's Theses

Strawberry production in California is limited by plant diseases such as Macrophomina root rot (MRR) caused by Macrophomina phaseolina, Verticillium wilt (VW) caused by Verticillium dahliae, and Botrytis fruit rot (BFR) caused by Botrytis cinerea. Current disease management strategies are compromised due to fumigant regulations or ineffective disease management practices. This thesis investigated methods to potentially improve the management of these three diseases. Two host plant resistance evaluations for MRR and VW were conducted for the 2022-2023 and 2023-2024 growing seasons. Sixty-three strawberry genotypes were screened in both years. All plants were exposed to the pathogen via artificial …

Understanding The Impact Of Fall Armyworm (Spodoptera Frugiperda) Feeding, And Drought Stress On Drought-Tolerant And Drought-Resistant Soybean (Glycine Max)., Adriana G. Peissel

Crop, Soil and Environmental Sciences Undergraduate Honors Theses

Drought and insect herbivory are two major stressors on high-value crops like soybean (Glycine max). However, few studies have explored how these stressors interact, despite their presence in tandem under field conditions. We investigated how drought stress and fall armyworm (Spodoptera frugiperda) caterpillar herbivory impact Magellan (drought-tolerant) and Blackhawk (drought-susceptible) soybean cultivars. The soybean plants were subject to four treatment groups (1. Drought 2. Herbivory 3. Drought + Herbivory 4. Well-Watered) during a treatment period of 7 days in a greenhouse. We then measured plant height, physiological traits, trichome density, soil moisture, and larval mass gain. …

Identification And Characterization Of Intermediate Phenotypes To Decipher Genetic Architecture Of Stalk Lodging Resistance In Maize (Zea Mays L.), Bharath Kunduru

All Dissertations

Maize is a key contributor to global food security and incurs severe yield losses due to stalk lodging, the permanent displacement of plants from an upright growth habit due to mechanical damage to the stem (stalk). Stalk lodging resistance, an indicator of the stalk ability to resist lodging, is a complex trait and determined by several structural, geometric, and material properties of stalks, collectively referred to as intermediate phenotypes, whose identity and genetic framework are poorly understood. Therefore, progress in resolving the genetic architecture of stalk lodging resistance was impeded by a lack of standardized phenotyping methodologies and a poor …

Understanding The Genetic And Metabolic Underpinnings Of Complex Traits In C4 Grasses, Manwinder Singh Brar

All Dissertations

Maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench) are two important cereal crops cultivated worldwide for food, animal feed, and industrial products. Productivity of these crops is significantly impacted by various biotic and abiotic stresses, such as diseases, insect pests, drought, salinity, and heat. Among factors influencing crop performance under stress, the regulation of leaf longevity plays a critical role in determining yield. Leaf senescence is a highly regulated process essential for nutrient remobilization through the degradation of cellular components in aging leaves, but premature or accelerated senescence reduces photosynthetic efficiency and yield. Staygreen, a phenotype …

Spatial Analysis Of American Chestnut (Castanea Dentata) Distribution And Ecology In Kentucky’S Federal Lands, Jacob Raymond Pease

Murray State Theses and Dissertations

Anthropogenic factors have been the cause of the decline of tree species across the globe. From unsustainable logging and development to disease and improper management, threats to forests have taken their toll. The American chestnut (Castanea dentata) was once an integral basal tree species in Appalachian forests, but chestnut blight drove the species to functional extinction by the mid-1900s. The recent creation of genetically modified chestnuts gives hope for future restoration of the species throughout its historical range. Despite blight resistance, effective restoration will require optimal site selection for finding and planting chestnuts, which will maximize limited resources. …

Identification Of A Stable Qtl For Juice Color In A Vitis Interspecific Hybrid ‘Chambourcin’- Based Population, Qiuni Yang

Graduate Theses/Dissertations

Berry juice color is one of the key factors influencing grape and wine quality, consumer preference, and marketability. While most previous studies on berry color have focused on the skin, research on juice color remains limited. This study investigated the genetic basis of berry juice color in a hybrid population derived from the Vitis interspecific hybrid ‘Chambourcin’ and V. vinifera ‘Cabernet Sauvignon’. A new nine-category visual scoring system was developed to assess juice color based on OIV 225. To achieve comprehensive precision and quantitative analysis, CIELAB parameters (L*, a*, b*), Hue, and Chroma were extracted from image-based measurements. Using berries …

Optimization Of Transformation And Regeneration In The Sunflower (Helianthus Annuus), Sara M. Kilar

Masters Theses

In addition to their value as prized ornamentals, sunflowers are important crop species due to the nutritional value and high oil content of the seeds. Sunflower oil is a significant contributor to global seed oil production, which can be used as a food additive and cooking agent as well as a raw material for biodiesel production. While traditional breeding efforts have led to the development of many unique cultivars, genetically modified variations have proven more difficult due to the recalcitrance of sunflower plants to genetic transformation. As a result, facile and efficient transformation methods for sunflowers have the potential to …

Investigate The Possibility Of Producing Healthier, Safer Peanuts Through Molecular Breeding And Novel Fungal Pathogen Management Strategies, Tariq Alam

All Dissertations

Peanut allergy, a critical health concern with high morbidity and mortality rates, is a leading cause of fatal anaphylactic reactions in the United States. Managing peanut allergy is challenging due to the prevalence of peanuts in processed foods and the risk of contamination. This dissertation evaluates the U.S. peanut mini-core collection for four major immunogenic proteins, Ara h1, Ara h2, Ara h3, and Ara h6, using gel electrophoresis, enzyme-linked immunosorbent assay, liquid chromatography, and mass spectrometry. The study identified 26 genotypes with reduced concentrations of allergenic proteins. Genome-wide association studies (GWAS) of protein traits revealed 10 significant SNPs and identified …

Comparison Of Statistical And Machine Learning Genomic Prediction Methods In Plant Breeding: Case Studies In Maize And Soybean, Igor Kuivjogi Fernandes

Graduate Theses and Dissertations

Plant breeding is essential to increase genetic gain and food production worldwide. This study was conducted to evaluate new ways to use machine learning (ML) to tackle plant breeding challenges, where two ideas were tested — the first chapter focuses on how to combine genetic and environmental data using ML to improve the prediction of maize grain yield in multi-environment trials, while the second chapter centers on how to couple feature selection of molecular markers with ML to enhance prediction of yield in soybean, and, in both cases, ML approaches were compared to well-established statistical methods greatly adopted by the …

Enhancing Crop Resilience: Physiological And Omics Approaches For Drought And Heat Stress Tolerance In Soybean And Peanut, Jyoti Prasad Kakati

All Dissertations

Soybean and peanut are two major crops globally grown for oil and protein. Climate change-associated factors like drought and increased temperature (heat stress) challenge the global production of soybeans and peanuts. Though the United States is the second-largest producer of soybean and the fourth-largest producer of peanuts, it still faces production constraints associated with drought and heat stresses. In the present study, we have examined the responses of soybean and peanut plants to drought and heat stresses during germination and reproductive phases. We conducted field and controlled environmental studies to elucidate the impact of drought stress on germination and seedling …

Leveraging The Genomic Tools To Explore The Molecular Basis Of Salinity Tolerance In Rice And Soybean, Rajat Pruthi

LSU Doctoral Dissertations

Salinity stress significantly challenges agricultural productivity, particularly affecting major crops like rice and soybean. This research investigates the genetic basis of salt tolerance in both crops through high-resolution genetic mapping, genome-wide association studies (GWAS), and RNA-Seq analysis. In rice, we examined quantitative trait loci (QTLs) associated with salt tolerance at the seedling and flowering stages using a population of advanced backcrossed introgression lines (ILs). A genetic map, constructed with 14,230 polymorphic SNP markers, identified distinct QTLs and candidate genes for salt tolerance at both stages, suggesting differential genetic controls. Notable genes such as OsHAK13 and OsCYP21-4 were upregulated under salt …

New Insights On Hybridization In Potamogeton Floridanus (The Florida Pondweed), Kaitlyn R. Sampson

Graduate Theses and Dissertations (2019 - present)

Freshwater ecosystems are some of the most important and highest threatened habitats in the world, and aquatic plants play an important, but often-overlooked, role in maintaining them. Potamogeton is a diverse and ecologically important aquatic plant genus well known for taxonomic difficulty and rampant hybridization. lbis study aimed to 1) test the hypothesis that Potamogeton jloridanus (Florida pondweed) is a hybrid between P. oakesianus and P. pulcher, and 2) to investigate correlations in ecological conditions for the focal species. This study revealed the discovery of a new population of P. jloridanus in Big Coldwater Creek in Santa Rosa Co., FL, …

Evaluating Past Progress And Assessing Prediction Breeding Strategies For Sustained Genetic Gains In The Louisiana Sugarcane Variety Development Program, Brayden A. Blanchard

LSU Doctoral Dissertations

The aim of this dissertation is to outline important considerations for the Louisiana Sugarcane Variety Development Program (LSVDP) as it pertains to historical progress, impact, goal setting, and new strategies for continued genetic gains. Industry progress was evaluated with robust regression models to quantify rates of productivity gains. Over the last 50 years, statistically significant productivity gains were identified in sucrose content (45%), cane yield (32.2%), and sugar yield (93%) while pairwise comparisons of decades showed that progress was incremental rather than rapid and sustained once achieved. The decade from 1990-1999 was identified as the only decade with a significant …

Isolation Of Gametophytic Selection And Selective Embryo Abortion In Mimulus Guttatus, Desmond C. Willson

University Honors Theses

A lack of genomic studies examining gametophytic selection (GS) and selective embryo abortion (SEA)--which occur during the reproduction of angiosperms--leaves questions regarding the adaptive and evolutionary effects of these processes. Analyzing deviations from Mendelian segregation offers an avenue for identifying loci targeted by GS and SEA, and their contributions to purging of genetic load. However, other selective processes such as meiotic drive and cytonuclear interactions, as well as pollen and ovule abortion, can cause distortion. To distinguish the effects of GS and SEA from other causes of distortion, we will perform reciprocal crosses between highly homozygous and highly heterozygous individuals …

Identification Of Downy Mildew Resistance In Wild Arugula And Evaluation Of Downy Mildew Causing Pathogens And Management Practices, Reilly B. Blair

Master's Theses

Downy mildew has been a potentially devastating constraint to crop production within the Brassicaceae family worldwide (CABI, 2022) and on the Central Coast of California (Smukler, et al, 2008; Koike, et al. 2007). Downy mildew is a foliar disease, caused by the pathogens in the Hyaloperonospora genus on plants within the Brassicaceae family (Goker, et al, 2009). Downy mildew is a disease that is common in region of the world with Coastal climates that provide humidity and moderate temperatures (Sarahan, et al, 2017). Crops within the Brassicaceae family maintain a predominant role in agricultural systems worldwide (Cartea, et al, 2011) …

Transcriptomic Profile Of Armillaria Root Rot Fungi Affecting The U.S. Stone Fruit Industry, Jared Weaver

All Theses

Armillaria Root Rot (ARR) is a significant replant disease threatening the future of the United States stone fruit industry. Economic loss in South Carolina peach orchards is estimated to be $8M annually due to approximately 3-4% of annual tree deaths caused by ARR on replant sites. Management solutions are insufficient and can at best extend the life of the orchards on replant sites. The only solution to solving the ARR problem, apart from abandoning the replant site for peach production, is planting orchards on ARR-resistant rootstock. Significant progress has been made towards providing growers with genetically resistant rootstock, however, for …

Enhancement Of Applied Rice Breeding Programs: Exploring Factors Impacting Genomic Selection Accuracy And Discovery Of A Novel Gene For Grain Shape, Maria G. Montiel

LSU Doctoral Dissertations

Plant breeding is a crucial tool in addressing global challenges such as climate change, population growth, and the need for more resilient crops. Rice serves as a staple food for a significant portion of the global population and has served as a model crop for genetic and genomic studies. Genomic selection (GS) has become valuable tool in plant breeding, allowing breeders to predict breeding lines’ performance based on their genotypes. The training (TS) set is a central component of genomic selection and the optimization of the training set is crucial for efficient implementation of genomic selection. The first two objectives …