Digital Commons Network^™

The Floral Thermal Environment: Physical, Morphological, And Environmental Determinants, And Their Impact On Plant-Pollinator Interactions, Jennifer Apland

All Theses

Anthropogenic climate change is driving major shifts in global temperatures and increases in extreme temperature events that contribute to reduced survival and species loss. To counteract extreme temperatures, many organisms can undergo geographic range shifts or engage in behavioral thermoregulation (e.g., movement to suitable microhabitats). While plants are sessile and thus subject to highly variable ambient temperatures, they have evolved mechanisms to regulate internal floral temperature. Floral thermoregulation may mitigate thermal stress on pollen and ovules and impact plant-pollinator interactions. These mechanisms for thermoregulation are often highly dependent on ambient temperature and solar radiation as most plants are not endothermic. …

A Genome Wide Association Study Of Heat Tolerance In Snap Bean (Phaseolus Vulgaris), Morgan Stone

All Theses

Bean production in the United States has decreased while the temperatures have been steadily increasing, reaching new highs each year. Heat stress is detrimental to common bean (also known as snap bean) production. Symptoms of heat stress include decrease in pollen viability, shriveling of pods, and pod abortion making them unmarketable. Pod production of 323 snap bean accessions from a large diversity panel was assessed in a randomized complete block design with field trials at two different times in the spring season. The results show a significant decrease in the number of pods produced per plant and weight of pods …

Enabling Breeding For Fruitlet Freeze Tolerance In Peach, Ufuk Caglar

All Theses

Climate change is affecting the production of temperate fruit crops, with cold temperatures emerging as a critical abiotic stressor that limits plant growth and performance. Freeze damage, particularly in spring, has resulted in significant economic losses in peach production in the southeastern United States. Research efforts in peach and other Prunus species have primarily focused on studying dormancy-related traits associated with bloom time, such as chill and heat requirement, with fruitlet freeze tolerance not equally represented. Breeding for climate resilience in peach requires a combination of these traits to allow for late bloom via targeted chill requirement and high heat …

Germination Trends Of American Chaffseed, Schwalbea Americana L., And Factors Affecting First-Year Seedling Development, Trenton Miller

All Theses

Following centuries of exploitation and fire suppression, longleaf pine systems are now the focus of many conservation efforts. Efforts to restore populations of Schwalbea americana L. in longleaf pine savannas have been met with frustratingly low recruitment. While past studies have briefly quantified germination rates for Schwalbea, there have not been any studies yet that truly investigate this plant’s germination requirements. Additionally, there has been little research into characterizing the parasitic relationship between Schwalbea and its various host species. We conducted a germination study in a growth chamber that investigated Schwalbea’s germination rate and time to germinates as …

Rapid Leaf Senescence Symptoms Are Related To Carbohydrate Depletion In Cut Chrysanthemums, And Strategies For The Symptoms Reduction, Shara Ortiz Carvajal

All Theses

Chrysanthemum (Chrysanthemum ×morifolium) is the second-largest exported cut flower worldwide; however, some cultivars exhibit rapid leaf senescence during their first week of vase life. This phenomenon negatively impacts consumer perception of plant quality, and its cause has been unknown. Experiments were performed in Colombia on cut chrysanthemums shipped to the U.S. for vase-life evaluation. After 10 d, the severity of leaf senescence symptoms was recorded. Experiments examined the effect of flower form [disbud (one flower per stem) versus spray (5-10 flowers per stem)], the effect of time of harvest (A.M. versus P.M.), and sugar sources (dextrose, fructose, mannitol, and sucrose) …

Salinity In Propagation: Germination And Juvenile Acclimatization Of Wetland Halophytes Using Saline Irrigation, Morgan Tomlin

All Theses

The introduction of poor water quality into commercial nursery crop production is predicated on optimized methods that apply saline irrigation without compromising plant success and health. Halophytes have many mechanisms of salt tolerance; however, these are greatly tied to physiological and developmental maturity. Thus, evaluating salt tolerance of halophytic crops (Hibiscus moscheutos and Kosteletzkya virginica) during seed germination and juvenile phases of life may provide insight into the efficacy of integrating poor quality water in horticultural operations.

Four seed priming methods (hydropriming, proline priming, low concentration halopriming, and high concentration halopriming) were evaluated as pre-sowing techniques to ameliorate …

Development Of New Cotton Defoliation Sprayer Using Unmanned Ground Vehicle And Pulse Width Modulation Technology, Jyoti Neupane

All Theses

Chemical spraying is one of the most important and frequently performed intercultural agriculture operations. It is imperative to utilize appropriate spraying technology as a selection of ineffective one leads to waste of agrochemicals to the non‐target area. Several precision technologies have been developed in the past few decades, such as image processing based on real‐time variable‐rate chemical spraying systems, autonomous chemical sprayers using machine vision and nozzle control, and use of unmanned aerial and ground vehicles. Cotton (Gossypium hirsutum L.) is an important industrial crop. It is a perennial crop with indeterminate growth habit; however, in most parts of the …

Survey And Prevalence Of Palmer Amaranth Herbicide Resistance In South Carolina, Mitchell Williams

All Theses

Palmer amaranth is a troublesome weed for growers to control, not only due to its aggressive growth characteristics that limit row-crop production, but because of its resistance to different herbicide modes of action. The first case of herbicide resistance in Palmer amaranth was detected in 1989 and has since grown to nine different herbicide classes throughout the United States. New herbicide modes of action have not been developed since the 1980s, so proper stewardship of the remaining modes of action is important for effective control of Palmer amaranth. Increased herbicide resistance from states bordering South Carolina have been reported; therefore, …

Use Of Biorational Products For Botrytis Management In Floriculture Crops, Josselyn Calidonio

All Theses

Botrytis cinerea is an important pathogen that has a significant economic impact on the floriculture industry from propagation to the postharvest environment. Chemical fungicide applications have been one of the main approaches that growers use for botrytis blight management; however, studies have shown that the indiscriminative use of these chemicals leads to fungicide resistance (Brent and Hollomon, 1998; Fillinger and Elad 2016). This thesis explores the potential use of biorational products for botrytis blight management. Biorationals are defined as compounds that have low or no direct mammalian toxicity and few effects on the environment (Paulitz and Belanger 2001). A review …

Identifying Genetic Sources Of Anthracnose Resistance In Global Sorghum Lines, Mary-Frances Behnke

All Theses

Anthracnose of sorghum (causal agent: Colletotrichum sublineola) is the most detrimental disease of sorghum (Sorghum bicolor) worldwide, significantly reducing grain yield. This study includes a literature review of the disease and a meta-analysis of genome-wide association studies (GWAS) of anthracnose-resistance in sorghum as means to elucidate genetic sources of the trait. The meta-analysis includes genotypic and phenotypic data from 5 unique studies and 1,071 sorghum lines. Original genotyping-by-sequencing data from were obtained primarily from National Center for Biotechnology Information’s Sequence Read Archive (NCBI-SRA) and prepared and processed using the Tassel 5 GBS v2. pipeline. Phenotypic data were …

Screening For Dmi And Mbc Fungicide Resistance In Monilinia Fructicola And Evaluation Of Biorational Products For Control Of Brown Rot On Peach In The Southeast United States, William Gura

All Theses

Monilinia fructicola (G. Winter) Honey is a fungal pathogen and is the causal agent of blossom blight, twig blight, green fruit rot, preharvest brown rot, and postharvest brown rot of peach (Prunus persica (L.) Batsch). Especially pre-and postharvest brown rot can have devastating economic impacts and negatively effects yield for peach growers throughout the southeastern United States. The most effective method for the control of pre- and postharvest brown rot is the application of synthetic fungicides during preharvest season. However, the consecutive use of fungicides with the same mode of action potentially give rise to resistance. This thesis focuses …

Evaluating The Effect Of Biochar Soil Amendments On Belonolaimus Longicaudatus Populations Damaging Bermudagrass In South Carolina, Malone Thomason

All Theses

Belonolaimus longicaudatus Rau, (1958) (sting nematode) is a prevalent plant-parasitic nematode found in association with Cynodon spp. (bermudagrass) in South Carolina (Ye et al., 2012). Due to the persistence of the pest, long-term management strategies are necessary. Applications of biochar and compost amendments have reduced nematodes in various crop systems, but research on turfgrass systems is limited. The objectives of the studies were to determine: (1) The effect of topdressing or soil incorporated biochar amendments on sting nematode populations, and (2) The effect of topdressing or soil incorporated amendments on turf quality. A field study was established to examine topdressings …

Patterns And Drivers Of Wiregrass Gap Longleaf Pine (Pinus Palustris Mill.) Woodland Succession As Part Of Restoration Efforts, Armin Weise

All Theses

Longleaf Pine (Pinus palustris) communities are widespread throughout the Southeastern United States with a dominant understory vegetation of wiregrass (Aristida spp.) in most of its range. A small area in central South Carolina that is naturally free of wiregrass is called the “Wiregrass Gap”. Here, the understory vegetation is dominated by bluestems grasses (Andropogon spp. and Schizachyrium spp.) which drive the disturbance regime of frequent low-intensity fire. The successful establishment of these grasses is key for longleaf pine woodland restoration efforts in this region, but few resources detail the ecological drivers at play that enable successful restoration in these longleaf …

Meta-Analysis Of The Effects Of Endophytes And Their Secondary Metabolites On Herbivory From Insects, Derrick Taylor

All Theses

Endophyte-infected plants have reduced the level of herbivory. The defense to herbivory can vary due to the metabolites in the plant and the method of feeding from the pest. Secondary metabolites produced by the endophytes are mainly alkaloids. The associations between endophytes and some alkaloid groups are studied in greater detail. The lack of research of certain alkaloid groups ultimately means that some alkaloids had more data that could be analyzed. As a result, the alkaloid groups were not evenly represented in the meta-analysis. The meta-analysis analyzed the relative effectiveness of the metabolites or endophytes in each of the articles …

Winter Cover Crop Performance In The Southern Piedmont Region Of South Carolina, Payton Davis

All Theses

Cover crops (CC) offer in-field and environmental benefits when integrated into cropping systems. Low CC adoption in the southern Piedmont of South Carolina is partially due to the lack of information on CC performance and benefits within the region. To address this, eight winter CC and a fallow/pigweed treatment were investigated for their influence on soil temperature, volumetric water content (VWC), percent cover, biomass, and the occurrence of soil water repellency (SWR). A randomized complete block design experiment was conducted in the fall and winter of 2021-2022 (EXP A) and repeated in 2022-2023 (EXP B). Cover crops minimally influenced soil …

Influence Of Potassium Fertilizer Application Timing On Cotton Production As Related To Soil Potassium On U.S. Coastal Plain Soils, Shruthy Suresh Kumar

All Theses

Understanding soil K dynamics is highly significant in cotton production owing to its prominent role in cotton fiber quality. About 31 % of cotton production in the U.S. is concentrated in SE states, with coastal plain soils having low innate K availability. Crop fertilizer-K recommendations are primarily made worldwide and across the U.S. using pre-plant STK concentrations. A literature review on cotton K studies suggests that fertilizer-K recommendations based on pre-plant STK concentrations alone need fine-tuning to meet the increasing K demands in modern cultivars, variations in crop K requirement patterns, and varied soil K supplying capacity. Studies have been …

Precision Management Of Inputs In Cotton And Soybean Production In South Carolina, Kyle Smith

All Theses

The adoption of precision agriculture technologies and developing specific product use recommendations in cotton and soybean production could help farmers reduce input costs and optimize overall farm profitability. The objectives of this research were to evaluate whether or not the use of variable rate seeding in cotton could increase profitability and to determine the rainfast interval of commonly used insecticides in cotton and soybean production. The first trial, variable rate seeding in cotton, was implemented at the Edisto Research and Education Center near Blackville, SC across five years to evaluate variable rate seeding in cotton. Results from trials in South …

Characterization Of Colletotrichum Nymphaeae Isolates From Apple With Reduced Sensitivity To Fluazinam And Tebuconazole, Rulyu Meng

All Theses

Apple bitter rot is caused by Colletotrichum nymphaeae and other Colletotrichum species and management relies primarily on synthetic pesticides. Very few fungicides are effective against the disease and resistance has further limited their usefulness. A recent study indicated relatively low EC₅₀ values (the concentration required to inhibit 50% of mycelial growth in vitro) of C. nymphaeae isolates from Brazilian apples to fluazinam and tebuconazole, two fungicides that are not routinely used for bitter rot control. Isolates on opposite sides of the sensitivity range were designated either sensitive (lowest EC₅₀ values) and reduced-sensitive (highest EC₅₀ values). The objective …

Unmanned Ground Vehicle Proximal Sensing For Forage Biomass Production Estimations, Curtis Erwin

All Theses

A large increase in productivity could be realized by small increases in efficiency and utilization on grasslands due to their large area. Pre-harvest biomass estimations can help forage producers make better informed management decisions. Producers of dry hay and hay silage can better identify plant growth stages and the optimal time to harvest. Grazers can better determine the most efficient number of animals and stocking density. The goal of this study was to create a novel pre-harvest biomass estimation method utilizing compressed height combined with an unmanned ground vehicle (UGV). A compression plate named a “compression ski” was constructed and …

Addressing Meloidogyne Enterolobii Spread In The Sweetpotato Industry: Development Of A High Throughput Survey Detection Method For Root-Knot Nematodes And Quantification Of M. Enterolobii Damage On Storage Roots In Long-Term Assays, Julianna Culbreath

All Theses

Meloidogyne enterolobii is an aggressive root-knot nematode (RKN) species that has emerged as a significant pathogen of sweetpotato in the Southeastern US. Meloidogyne enterolobii is spread through the movement of infected ‘seed’ sweetpotatoes used for propagation, and the RKN resistance in commercial sweetpotato cultivars has proven ineffective against this nematode. This has prompted regulatory agencies to impose quarantines on regions infected with M. enterolobii. Sweetpotato storage roots can be rendered unmarketable due to M. enterolobii infection, resulting in potential overall yield loss. Visual detection of RKN in sweetpotato can be unreliable, and further distinguishing M. enterolobii from other RKN species …

In Vitro Rooting Techniques In Prunus Spp. For Propagation And Disease Screening For Armillaria Root Rot (Arr) Resistance, John Lawson

All Theses

Prunus is a genus widely cultivated to produce edible fruit including almond (P. amygdalus), peach (P. persica (L.) Batsch), cherries (P. avium and P. cerasus), among others. The cultivation of Prunus is economically important for several regions of the United States and relies on appropriate cultivars and rootstocks that are adapted to a growing region. Encroaching plant pathogens are forcing breeders to use sexually compatible germplasm from related species for introgression of novel alleles that confer tolerance or resistance. This is especially true in the rootstock breeding where interspecific hybridization is often used …

Potassium Level Prediction Of Peach Tree Leaves Using A Hyperspectral Camera And Multivariate Analysis, Megan Io Ariadne Salimbangon Abenina

All Theses

The use of hyperspectral imaging is a valuable piece of technology used in precision agriculture. Hyperspectral imaging system could help farmers and researchers alike in analyzing tissue samples quicker compared to the current way of running a plant tissue analysis on the different nutrient levels that often takes time in generating results. The objective of this research was to measure the potassium level of peach trees using its leaves with a hyperspectral camera. The Senop HSC-2 was used to capture images of peach tree leaves during the fall of 2020 and 2021. The collected data were used to create a …

The Influence Of Water Stress And Rootstocks On Nutrient Uptake And Gas Exchange Of Young Peach Trees, Naif Alshammari

All Theses

Young peach trees are often rainfed in the southeastern U.S. and periods of dry weather can cause tree water deficit that can be detrimental to orchard productivity. There is a lack of understanding of the influence of water regimes and rootstocks on the nutritional status and gas exchange of the peach tree. Most peach growers in Southeastern United States do not irrigate their young peach trees because they do not produce fruit until the third leaf. In this region, peach growers use Guardian as a rootstock, although MP-29 is also interesting for growers with orchards that have Armillaria root rot …

Identifying Temporal Sensitivity Of Poinsettia Flowering To High Temperatures, Paul Millar

All Theses

High temperatures can cause delayed flowering in poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch), a phenomenon known in the industry as heat delay. The poinsettia wholesale market is concentrated to a relatively brief period from early-November through early-December putting growers at risk to heat delay. This problem is compounded by the unusual weather patterns created by climate change. The objective of this thesis was to identify periods in which poinsettia flowering is sensitive to high temperatures. First, the weeks within the growing season when the plants were sensitive to high temperatures were identified (Chpt. 2). Then within those sensitive weeks, …

Characterization Of Colletotrichum Nymphaeae Isolates, Causal Pathogen Of Apple Bitter Rot, With Reduced Sensitivity To Fluazinam And Tebuconazole, Rulyu Meng

All Theses

Apple bitter rot is caused by Colletotrichum nymphaeae and other Colletotrichum species and management relies primarily on synthetic pesticides. Very few fungicides are effective against the disease and resistance has further limited their usefulness. A recent study indicated a relatively low range of EC₅₀ values (the concentration required to inhibit 50% of mycelial growth in vitro) of C. nymphaeae isolates from Brazilian apples to fluazinam and tebuconazole, two fungicides that are not routinely used for bitter rot control. Isolates on opposite sides of the range were designated either sensitive (lowest EC₅₀ values) and reduced sensitive (highest EC_{50 …}

Pre-Breeding Of Kale (Brassica Oleracea Var. Acephala) – Organic Adaptation And Shelf Life, Craig Reda

All Theses

Kale (Brassica oleracea var. acephala) is a nutritionally rich leafy green that that contains vitamins, minerals, and prebiotic carbohydrates. As a popular organic crop, kale accounted for 1.3% of total US organic produce sales in 2020, a market valued at over 17 billion USD. However, organic production is limited by its inability to use synthetic pesticides and fertilizers and suffers from decreased yield when compared to conventional agriculture, partially due to the creation of a significantly different growing environment. Additionally, the absence of synthetic products can also negatively impact the shelf of leafy greens like kale. To determine …

Distribution And Genomic Diversity Of Pollen-Borne Viruses And Viroids At The Interface Of Peach And Wild Prunus Spp. In The Southeastern United States, Fabian Omar Rodriguez Bonilla

All Theses

Prunus necrotic ringspot virus (PNRSV), prune dwarf virus (PDV), and peach latent mosaic viroid (PLMVd) are important pollen-borne pathogens that affect peach orchards in the southeastern United States. My aim with this research is to identify potential sources of virus/viroid inoculum sources in the wild and determine pathogen movement and interactions between wild Prunus spp. and cultivars of peach (P. persica). In Chapter I, I review the literature on pollen borne viruses and viroids in peach. In Chapter II, I surveyed for these pathogens near peach production areas in South Carolina and Georgia, sampling from three endemic wild …

Floating Treatment Wetlands For Brackish Waters: Plant Selection And Nutrient Uptake Potential., Andrea Landaverde

All Theses

Brackish water bodies in coastal regions provide critical ecosystem services that support human and environmental health. Anthropogenic activities such as agricultural and industrial activities, construction, urban settlements, and tourism contribute to increased inputs of nitrogen (N) and phosphorus (P) in brackish coastal ecosystems. Excess nutrients can lead to impaired water quality and affect marine organisms. Floating treatment wetlands (FTWs) are a vegetated-base technology used to remove contaminants from water column, that has been mainly studied and applied in freshwater systems. Application of FTWs in brackish systems requires further investigation, as high salinity in brackish waters could result in toxicity to …

Identification Of Cytospora Species Isolated From Canker In Peach Trees In South Carolina, Stephen T. Baker

All Theses

In 2016, a survey was conducted into the causes of twig blight on peach (Prunus persica) in five orchards across South Carolina. From this survey, isolates from the fungal genus of Cytospora (Sordariomycetes, Diaporthales) were reported on peach, for the first time, within the state. Cytospora species are known to cause oozing cankers on a wide range of woody hosts leading to dieback, loss of limbs, and reduction in yield, prompting concern for important economic crops. Past methods of identification of Cytospora species have been confounded by indistinguishable morphology, overlapping host preference among species, and genetic sequencing …

Elucidating The Cellular Physiology Of Glyphosate Resistance In Palmer Amaranth (Amaranthus Palmeri) Using Integrated Omics Approaches, Pawanjit Kaur Sandhu

All Theses

The evolution of resistance to herbicides in weeds poses a major threat to agricultural production systems. To date, herbicide resistance has been reported against 21 modes of action in 266 weed species across 71 countries. More than 50 weed species have developed resistance against glyphosate, the most widely used herbicide worldwide. Although several mechanisms of glyphosate resistance have been discovered, our understanding of alterations in the cellular physiology of glyphosate-resistant weed biotypes, and the induction of the resistance mechanisms remains limited. This knowledge is critical to developing sustainable weed management practices and for a comprehensive understanding of plant stress adaptations. …