Plant Pathology Commons^™

Npr1 As A Temperature-Sensitive Regulator Of Pipecolic Acid-Mediated Plant Systemic Immunity, Spencer Tout

Theses and Dissertations (Comprehensive)

Healthy plant development requires balancing both abiotic (e.g. climate) and biotic (e.g. pathogen) challenges, which intercept important signaling pathways in plants. For example, climate change-associated elevated temperature can negatively modulate various aspects of plant immunity, including the production of central immune signals salicylic acid (SA) and N-hydroxypipecolic acid (NHP). Since SA and NHP signaling both require the master immune co-activator protein NON-EXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1), it is important to investigate NPR1 as a potentially temperature-regulated molecular hub. Although the NPR1 gene is not transcriptionally downregulated at elevated temperatures (28° C vs. 23° C), little is known about …

Identification And Characterization Of The Antimicrobial Activities Of Pseudomonas Sp. Strain Wp18, Emma Suzanne Willis

Theses and Dissertations

Strain WP18 was isolated from disease suppressive soil of a soybean rhizosphere in the Mississippi Delta. Phylogenetic analysis supported that strain WP18 could represent a novel species within the genus Pseudomonas. This conclusion is supported by genome-wide bioinformatic analyses such as average nucleotide identity and genome to genome distance calculations. Further studies are needed to claim a novel bacterial species, which include cell fatty profiles, fingerprinting analysis, and polar lipid analysis based on the International Code for Nomenclature of Prokaryotes. Strain WP18 showed a broad-spectrum of antimicrobial activity against plant pathogenic bacteria and fungi that are economically important in agriculture, …

Evaluation Of Pierce’S Disease-Resistant Grapevine Cultivars In Upstate South Carolina, Annie Bruno

All Theses

Interest in wine grape production is increasing in South Carolina, but Pierce’s Disease (PD) caused by the xylem-limited bacteria Xylella fastidiosa (Xf) is a major limiting factor. Xf is spread by sap-sucking insect vectors in the Cicadellidae family such as sharpshooters. In the United States, Xf has become endemic to the southeast as global temperatures rise, causing winter temperatures to increase, which allows the bacteria to survive year-round. However, PD-resistant grapevine hybrid cultivars have become available through breeding V. vinifera genes with native American Vitis species that are resistant to Xf. In this study, the PD-resistant grapevine …

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 …

Advancing Molecular Tools For The Study Of Rubus Viruses, Andrea Sierra-Mejia

Graduate Theses and Dissertations

Since blackberry yellow vein disease (BYVD) was first described, the blackberry virome has expanded significantly. BYVD is a complex disease associated with over ten viruses, yet the role of each virus in its etiology remains understudied. Studying the effect of each virus in disease development requires the identification of single infections; however, this task has been difficult for BYVD, with all field collected material over the past two decades consistently found infected by multiple viruses. Given the diversity of viruses associated with the disease and their different modes of transmission, obtaining pure virus cultures necessitate transmission of individual viruses via …

Induced Systemic Resistance Against Nematodes By Plant Growth-Promoting Microbes In Potatoes, Cole Grannan

Master's Theses

Biofertilizers consist of plant growth-promoting microorganisms that establish symbiotic relationships with plant roots and stems. These beneficial microbes play a crucial role in enhancing plant defenses against various threats including insects, nematodes, and microbial pathogens. The purpose of this study was to investigate the effectiveness of two fungal biofertilizers (an endophytic strain of Beauveria bassiana (BA) and a mixture of arbuscular mycorrhizal (AM) fungi), specifically their ability to induce systemic resistance against plant- parasitic nematodes (PPNs) in potatoes (Solanum tuberosum cv. Masquerade) under controlled greenhouse conditions. The study utilized soil collected from Colorado State University’s San Luis Valley (SLV) Research …

Evaluating The Duckweeds Lemna Minor And Spirodela Polyrhiza As Alternative Aquatic Hosts For The Spread Of The Bacterial Wilt Pathogen, Ralstonia Solanacearum, Irelynn Smith

Honors Theses

Ralstonia solanacearum is a plant pathogen that causes bacterial wilt disease in major crops such as tomatoes and potatoes. Recently, this bacterium was discovered in floating pennywort (Hydrocotyle ranunculoides) and Pennsylvania smartweed (Polygonum pennysylvanicum), two previously unsuspected aquatic plants. Duckweed is an aquatic plant with a high level of resilience and short doubling time. Common duckweed (Lemna minor) has previously demonstrated its capability as a versatile high-yield infection model for other types of pathogenic bacteria. Given this newfound branch of aquatic hosts and the fact that duckweed is a common pond weed previously identified in several ponds located nearby infected …

Soybean Cyst Nematode (Heterodera Glycines Ichinohe) Virulence Assay Against Resistance Sources In Nebraska, Pratibha Karki

Department of Plant Pathology: Dissertations, Theses, and Student Research

Soybean cyst nematode (SCN, Heterodera glycines Ichinohe), one of the major yield-limiting pathogens of soybean, is currently found in 60 counties of Nebraska that produce more than 90% of the state’s soybean. Often, yield loss occurs without any above-ground symptoms, which makes it difficult to manage. The primary management option is the use of SCN-resistant varieties. Several soybean plant introductions serve as resistance sources against SCN. Unfortunately, the single source, PI 88788, is used in approximately 90% of resistant varieties and its prolonged use has increased the virulence status of SCN in the U.S. A study was conducted to assess …

Field Prevalence Of Ring Nematodes In South Carolina And Its Potential To Predispose Peanut Pods To Aflatoxin Contamination, Sarala Giri

All Theses

Peanut ring nematode, Mesocriconema ornatum is a nematode pest of peanut which can cause necrotic lesions on pods, pegs, and roots. It has been reported to facilitate secondary infections in peanut and other crops resulting in more significant losses in yield and quality. Aspergillus flavus is a ubiquitous facultative saprophyte that produces aflatoxin, the most problematic mycotoxin for global health and economy. Experiments were conducted at the Edisto Research and Education Center of Clemson University to examine the relationship of ring nematode populations at pegging and harvest with aflatoxin concentration in peanut kernels due to infection by A. flavus …

Exploring The Physiological, Biochemical, And Enzymatic Responses Of Vigna Mungo Varieties To Mungbean Yellow Mosaic India Virus (Mymiv) Infection, Subham Dutta, Poly Saha, Mritunjoy Barman, R. Poorvasandhya, Moumita Panda, Tarique Ahmed, Thomas Wilbur Davis, Bulbul Ahmed, Mudagadde G. Deeksha, Jayanta Tarafdar

Department of Entomology: Faculty Publications

This study aims to enhance sustainable disease management in black gram by identifying varieties resistant to Mungbean Yellow Mosaic India Virus (MYMIV). We screened sixteen black gram genotypes, assessing physiological, biochemical and enzymatic basis. Results revealed a range of resistance levels, with PANT URD-19 showing the highest resistance (PDI 0.47%) and Pejua the lowest (PDI 37.24%). Seven genotypes demonstrated strong resistance, highlighting the necessity for targeted breeding. Variations in leaf thickness, trichome density, stomatal frequency, and epicuticular wax content were significant, with resistant varieties like LBG-888 and PANT URD-19 exhibiting thicker leaves, higher trichome density, and more wax, correlating with …

Exploring Mechanisms Of Chemical Resistance In Xanthomonas Arboricola Pv. Pruni And Strategies To Mitigate Resistance And Improve Disease Control, Milan Panth

All Dissertations

Xanthomonas arboricola pv. pruni (XAP) is a phytopathogenic bacterium that causes bacterial spot of peach. It causes spotted lesions on leaves and fruit, leading to early defoliation and unmarketable fruit, respectively. The pathogen can overwinter in twig cankers, which serve as the primary initial inoculum source for the next season’s leaf and fruitlet infection. The current disease management practice mainly relies on routine application of chemical bactericides containing copper or oxytetracycline (OTC) in the growing season. However, disease incidence can still be high despite chemical control measures in warm, rainy seasons.

Frequent applications of copper and OTC in United …

Biostimulant And Antagonistic Potential Of Endophytic Fungi Against Fusarium Wilt Pathogen Of Tomato Fusarium Oxysporum F. Sp. Lycopersici, Marie Cecile Muhorakeye, Everlyne Samita Namikoye, Fathiya M. Khamis, Waceke Wanjohi, Komivi S. Akutse

All Peer-Reviewed Publications

Endophytic fungal-based biopesticides are sustainable and ecologically-friendly biocontrol agents of several pests and diseases. However, their potential in managing tomato fusarium wilt disease (FWD) remains unexploited. This study therefore evaluated effectiveness of nine fungal isolates against tomato fusarium wilt pathogen, Fusarium oxysporum f. sp. lycopersici (FOL) in vitro using dual culture and co-culture assays. The efficacy of three potent endophytes that inhibited the pathogen in vitro was assessed against FWD incidence, severity, and ability to enhance growth and yield of tomatoes in planta. The ability of endophytically-colonized tomato (Solanum lycopersicum L.) plants to systemically defend themselves upon exposure to FOL …

Towards An Ideal Seed Coating, J M. Scott

IGC Proceedings (1977-2023)

Coated pasture seeds have been formulated in the past based largely on "trial and error" with relatively few objective criteria being employed to define desirable formulations, A description of desirable propelties of various layers of seed coatings and of the seeds themselves is presented.

Lolium Endophyte Viability: Effect Of Seed Storage, M P. Rolston, J R. Crush, M D. Hare, K K. Moore

IGC Proceedings (1977-2023)

The effects of seed storage on the endophyte Acremonium lolii in ryegrass (Lolium perenne L.) were evaluated over 7 years. The long• term effects of 4 seed moisture contents (SMC) 8.6-13.1 %: tempemture (ambient, 5, O, -15°C) 'aitd packaging types: calico, polyethylene fi,Jm. 9-140 µm, and aluminium-polyethylene (AIP) on endophyte viability were assess·ed. • Endophyte viability was maintained by lower seed moisture content and low temperatures. In ambient warehouse conditions endophyte viability declined to zero in 12 months in calico bags,' but was maintained for 3 years at 8.6% SMC in AIP: • Endophyte viability was maintained for …

Effect Of Dormancy-Releasing Treatments On Germination Of Bahiagrass Seed, J. Jeffrey Mullahey, D S. Fisher

IGC Proceedings (1977-2023)

Low seed germination and dormant seed in bahiagrass (Paspalum nonatutum Flugge.) necessitate high seeding rates for successful pasture establishment. A study of dormancy-releasing treatments and age of seed on germination of bahiagrass was conducted in an incubator at the Southwest Florida Research and Education Center near Immokalee, Florida. Five seed treatments (Crop-Start (Solid Matrix Seed Priming, Kamterter Products Inc., Lincoln, NB), potassium nitrate (KNO3), heat/humidity, palea removed, and a check), 2 cullivars (Pensacola, Tifton 9) of bahiagrass and 2 ages (10 and 16 months) of seed were used. A significant (P<0.05) age ·x treatment interaction occurred for all response variables. Based on total germination at 28 days, % dormant seed and rate of germination, Crop-Start and heat/humidity were consistently the best treatments. Additional research on germination with dormancy-releasing treatments is needed to study the Interaction of seed age and bahiagrass cultivar.

Weed Seed Contamination: Use Of A Seed Testing Database To Identify Processing Limitations, J S. Rowarth, M P. Rolston, A A. Johnson

IGC Proceedings (1977-2023)

A computerised database maintained by the Official Seed Testing Station of New Zealand provided the opporlunity to survey weed seed contamination in clover and grass seed-lots. Broad-leaf weeds such as Slierardia arvensis, Stellaria ,nedia and Chenopodium album were the major contaminants in Trifolium repens seed-lots. In grass seed-lots the main contaminants were seeds of other grasses such as Bromus hordaeceus, Vulpia spp. and Holcus lanatus. Weed seeds were found to be a major reason for downgrading or rejection from certification of clover and grass seed-lots in New Zealand; this reflects strict quality control measures.

An Investigation In To The Effect Of Some Factors On The Germination Of Erodium Seeds, Myrna Johnston, Alfredo Olivares, Gladys Fernandez

IGC Proceedings (1977-2023)

Erodiurn seeds present variable dormancy in and even within each species. Thus, it is important to know the factors that determine this variation as related to the persistence of its species. E. rnoschatmn and E. rnalacoides seeds were collected at the end of the annual cycle at La Rinconada de Maipli (33°28'S and 7S050'W). Effects of seed sour.ce (collecting in 1986, 1988 and 1990), age (keeping seeds under laboratory conditions) and maternal factors (cutting plants at early flowering) were analysed. Seeds were tested for germination capacity and germination rate at a constant temperature of 15°C on Petri dishes provided with …

Long-Term Seed Dormancy In Poa Pratensis L. Northern Norway, Trygve S. Aamlid, Dagfinn Arntzen

IGC Proceedings (1977-2023)

Inadequate gennination has often been obseived when planting Poa pratensis L. cv. Lavang (69°N) in northern Norwegian grasslands. This investigation was intended to elucidate whether this was due lo long­term seed dormancy, Seed-lots grown in different years in northern and southern Norway and stored at O-to•c, were germinated in Jakobsen­type germinators al various combinations of temperature and light. Significant dormancy was expressed at 21 °C even after 10 years of storage. Al this constant temperature, germination was promoted by 8 h fluorescent light compared with darkness and continuous light. Al 21/ I 2°C alternating temperature, seed genninated well irrespective of …

Seed Vigour In Lucerne And White Clover, Y R. Wang, J G. Hampton

IGC Proceedings (1977-2023)

Accelerated ageing (AA) was used to assess the seed vigour of 5 lucerne (Medicago sativa L, cv. Wairau) and 8 white clover (Trifolium repens L. cv. Grasslands Huia) seed-lots. Germination prior to AA ranged from 86-94% and 87-94% for the lucerne and white clover seed-lots respectively. All seed-lots hl\d been harvested in 1988 and were certified either as basic or first generation. Germination after 72 h at 40:t0.5°C (AA test) ranged frcim 31-76% for the lucerne seed­lots and 15-56% for che white clover seed-lots, indicating significant differences in seed.vigour among lots of both species. Time of ageing influenced …

Growing Methods For The Morphological Assessment Of White Clover Cultivars Purity, J G. Hampton, E J. Musukwa

IGC Proceedings (1977-2023)

Three growing methods (field sward, field spaced plants, glasshouse plants) were compared for the morphological assessment of white clover (Trifolium repens L.) cultivar purity. Three cerlified (breeders, basic and first generation) seed-lots of cv. Grasslands Kopu and one first generation Kopu seed lot which had been mixed with seed of another cultivnr (10:1) were used to generate data. After analysis of variance (ANOVA), significant (P<0.05) reductions from the breeders seed lot siandnrd for leaf size, stolon number and leaf length/width ratio were recorded for the mixed seed· 101 in nil three growing methods, and for petiole length with the sward method only. With the glasshouse and spaced-plant melhods, slolon numbers of the basic and first generation seed-lots were reduced (P<0.05), while leaf size was lower (P<0.05) for the first generation seed-lot in lhe glasshouse. However, under OECD certification requirements, leaf size of the mixed seed lot was the only characler for which "off types" were detecled. Data coefficients of variation were no greater for the glasshouse method than the required OECD plot-test method.