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Articles 91 - 113 of 113
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The Influence Of Commerce Silt Loam Soil Texture On Reproduction And Pathogenicity Of Rotylenchulus Reniformis On Cotton, Déborah Magalhães Xavier
The Influence Of Commerce Silt Loam Soil Texture On Reproduction And Pathogenicity Of Rotylenchulus Reniformis On Cotton, Déborah Magalhães Xavier
LSU Master's Theses
Greenhouse and microplot studies were conducted to evaluate the influence of soil texture on reproduction and pathogenicity of Rotylenchulus reniformis (reniform nematode) on cotton. A 45 day duration greenhouse experiment confirmed the pathogenicity of an isolate of R. reniformis from Avoyelles Parish on Stoneville LA887 cotton. A series of greenhouse experiments were conducted with three geographic isolates of R. reniformis (identified as Avoyelles, Evangeline, and Rapides to indicate the Parish of origin) on Stoneville LA887, Stoneville 5288B2F, and Phytogen 375WF cotton growing in soils with varying textures for 60 days. Soil types with sand, silt, and clay contents ranging from …
A Phylogenetic Analysis Of Species Diversity, Specificity, And Distribution Of Mycodiplosis On Rust Fungi, Donald Jay Nelsen
A Phylogenetic Analysis Of Species Diversity, Specificity, And Distribution Of Mycodiplosis On Rust Fungi, Donald Jay Nelsen
LSU Master's Theses
There are more than 7800 species of Pucciniales (rust fungi) described. Aeciospores and urediniospores of rust fungi are a food source for the larval stage of members of the fly genus Mycodiplosis, hence these could be of interest as potential biological control agents. Currently, Mycodiplosis contains 49 described species based on adult male morphology. A survey of 1,350 rust-infected plants from 44 countries was recently conducted to assess the occurrence of Mycodiplosis fly larvae across a broad spectrum of Pucciniales. Larvae were found on 261 collections from 25 countries. Statistical analyses explored the distribution of larvae in relation to host …
Influence Of Soil Nutrients On Reproduction And Pathogenicity Of Rotylenchulus Reniformis On Cotton, Herath Mudiyanselage Manjula Thaminda Kularathna
Influence Of Soil Nutrients On Reproduction And Pathogenicity Of Rotylenchulus Reniformis On Cotton, Herath Mudiyanselage Manjula Thaminda Kularathna
LSU Master's Theses
Among the variety of pathogens of cotton (Gossypium hirsutum), nematodes play a major role in reducing yield. Across the U.S. cotton belt, millions of dollars are lost annually due to nematode infestation. In the Mid-South and Southeast United States, root-knot nematode (Meloidogyne incognita) and reniform nematode (Rotylenchulus reniformis) are responsible for the highest percentage of damage. Crop rotation and nematicides are currently the most commonly used management strategies for nematode management. Soil fertility, which has a direct effect on plant growth, is also known to influence disease severity. Therefore, soil fertility would be an additional factor to consider for management …
Potential Roles Of Wrky Transcription Factors In Resistance To Aspergillus Flavus Colonization Of Immature Maize Kernels, Jake Clayton Fountain
Potential Roles Of Wrky Transcription Factors In Resistance To Aspergillus Flavus Colonization Of Immature Maize Kernels, Jake Clayton Fountain
LSU Master's Theses
The infection and colonization of maize (Zea mays L.) by the necrotrophic fungal pathogen Aspergillus flavus results in contamination of kernel tissues with carcinogenic mycotoxins known as aflatoxins, resulting in severe economic losses as well as negative effects on human and animal health. Resistance to A. flavus is mediated by both inducible and constitutively expressed defense proteins; however the mechanism regulating the expression of these defenses is poorly understood. This study examined the potential roles of six maize WRKY transcription factors, ZmWRKY19, ZmWRKY21, ZmWRKY53, ZmWRKY53.1, ZmWRKY67, and ZmWRKY68, in regulating defense responses against …
Comparative Genomics, Transcriptome Analysis And Characterization Of Selected Regulatory Genes Of Burkholderia Glumae, Felix Francis
Comparative Genomics, Transcriptome Analysis And Characterization Of Selected Regulatory Genes Of Burkholderia Glumae, Felix Francis
LSU Master's Theses
Burkholderia glumae is the primary causal agent of bacterial panicle blight of rice, which is becoming a major threat to global rice production. The genome of a highly virulent B. glumae strain, 336gr-1 that was isolated from rice in Louisiana, was sequenced to better understand the genome-scale characteristics, particularly that of its pathogenicity. Comparative genomic analyses with another strain, BGR1 that was isolated from Korea, revealed several unique regions present in the genomes of these two geographically separated phytopathogenic bacteria. Genome plasticity, primarily caused by a horizontal gene transfer, was observed in these closely related strains of Burkholderia that are …
Searching For Alternative Hosts And Determining The Variation In The Internal Transcribed Spacer (Its) Region Of Phakopsora Pachyrhizi And The Implications For Currently Used Molecular Diagnostic Assays: Subtitle, Tomas Allen Rush
LSU Master's Theses
Phakopsora pachyrhizi, the causal agent of soybean rust (SBR), is a serious disease on soybeans.The objectives of this project were to identify additional alternative and possible overwintering hosts of the SBR pathogen and to validate the current detection assays for SBR. For the first objective, we attempted to identify naturalized Louisiana legume(s) that can serve as hosts and overwintering sites for P. pachyrhizi. It was theorized that New Iberia and Iberville Parishes in south Louisiana are usually the first locations of soybean infection in the spring. This suggests that there may be alternative leguminous hosts located in these parishes that …
A Survey Of Ballistosporic Phylloplane Yeasts In Baton Rouge, Louisiana, Sebastian Albu
A Survey Of Ballistosporic Phylloplane Yeasts In Baton Rouge, Louisiana, Sebastian Albu
LSU Master's Theses
A study documenting basidiomycete yeast biodiversity was conducted in Baton Rouge, Louisiana during 2010 and 2011. Using the spore-fall method, the leaf surfaces of seven ferns were sampled at biweekly intervals. Maximum likelihood phylogenetic analyses of the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) of nuclear ribosomal DNA were used to identify 463 isolates representing 81 species spanning 12 orders within six classes in Basidiomycota. Nearly 30 of these isolates appear to be species new to science. Data indicate fern leaf developmental stage has an effect on the number of yeasts present. A …
A Systematic Study Of Xylella Fastidiosa Strains Isolated From Pecan, Grapevine, Oleander, And Sycamore In Louisiana, Rebecca Ann Melanson
A Systematic Study Of Xylella Fastidiosa Strains Isolated From Pecan, Grapevine, Oleander, And Sycamore In Louisiana, Rebecca Ann Melanson
LSU Master's Theses
Xylella fastidiosa causes disease in a number of economically important crops and landscape shrubs and trees including grapevine, citrus, oleander, and sycamore. In pecan, X. fastidiosa causes pecan bacterial leaf scorch (PBLS), which leads to defoliation and reduces nut yield. No economically effective treatments are available for PBLS. In order to improve PBLS management practices, it is necessary to determine the subspecies of X. fastidiosa strains that infect pecan so potential sources of inoculum can be identified. Multiprimer PCR and phylogenetic analyses using nucleotide sequence data from the 16S-23S rDNA intergenic transcribed spacer (ITS) region and pglA consistently identified strains …
Optimization Of Heat-Stable Protein Extraction In Recalcitrant Spartina Alterniflora, Yi Wang
Optimization Of Heat-Stable Protein Extraction In Recalcitrant Spartina Alterniflora, Yi Wang
LSU Master's Theses
Orthodox and recalcitrant seeds exhibit differential tolerance to water loss. Recalcitrant seeds are not able to tolerate desiccation and die when dried, while the orthodox seeds can be stored dry without losing viability for years. Spartina is a good model to study recalcitrance, because unlike most other recalcitrance studies, which contain only a recalcitrant species, this system has both recalcitrant S. alterniflora and orthodox species, S. pectinata and S. spartinae, as close-related physiological comparators. Lack of protective proteins, e.g. late embryogenesis abundant proteins (LEAs), has been proposed to be the cause of recalcitrant seed death. A common feature of these …
Characterization And Utilization Of Rice Defense Associated With Partial Resistance To Bacterial Panicle Blight: An Emerging Rice Disease Problem In The Southeastern United States, Bishnu Kumar Shrestha
Characterization And Utilization Of Rice Defense Associated With Partial Resistance To Bacterial Panicle Blight: An Emerging Rice Disease Problem In The Southeastern United States, Bishnu Kumar Shrestha
LSU Master's Theses
Rice is a staple food for much of the world’s growing population. Rice production is limited by a number of abiotic and biotic factors. These factors have direct effects on food security because less food is available to growing population. Bacterial panicle blight (BPB), caused by the bacterium Burkholderia glumae, is an emerging disease that causes grain rot, panicle discoloration, and unfilled grains in rice. Up to 70% of yield reduction has been reported in severely infected rice fields. No completely resistant rice cultivars have been identified, however, a medium-grain cultivar, Jupiter, showed a high level of partial resistance …
A Molecular Genetic Study On The Tofl/Tofr Quorum-Sensing System Of Burkholderia Glumae: The Major Pathogen That Causes Bacterial Panicle Blight Of Rice, Ruoxi Chen
LSU Master's Theses
Burkholderia glumae is the major causal agent of an economically important rice disease, bacterial panicle blight (BPB). The known virulence factors of B. glumae share the TofI/TofR quorum sensing system as their regulator. tofI and tofR genes encode the N-acyl homoserine lactone (AHL) synthase for the B. glumae quorum sensing signals, N-octanoyl homoserine lactone (C8-HSL) and N-hexanoyl homoserine lactone (C6-HSL), and the receptor for AHL, respectively. To better understand the relationship between quorum sensing and known virulence factors (toxoflavin, flagella and lipase), as well as, putative virulence factors (i.e. extracellular polysaccharide), mutagenetic and phenotypic analyses were applied to this study. …
Low Co-Cultivation Temperature At 20oc Improved Agrobacterium Tumefaciens-Mediated Transformation Of Tobacco Leaf Disks, Guiying Su
LSU Master's Theses
I investigated the effect of co-cultivation temperature and binary Ti vectors on the fresh weight yield of leaf disks of tobacco (Nicotiana tabacum L. cv. Xanthi (nn, Smith) after Agrobacterium tumefaciens-mediated transformation. I concluded that the temperature at 20ºC during co-cultivation of leaf disks with A. tumefaciens was the most critical factor on the reproducible enhancement of fresh weight yield. The highest fresh weight increase and presumably transformation efficiency was achieved under the following experimental conditions: A. tumefaciens strain LBA4404 containing pLSU binary Ti vector was grown overnight at 28oC in liquid Agrobacterium medium and the concentration was adjusted to …
Physiological, Biochemical And Molecular Characteristics Associated With Virulence Of Burkholderia Glumae: The Major Causative Agent Of Bacterial Panicle Blight Of Rice, Hari Sharan Karki
Physiological, Biochemical And Molecular Characteristics Associated With Virulence Of Burkholderia Glumae: The Major Causative Agent Of Bacterial Panicle Blight Of Rice, Hari Sharan Karki
LSU Master's Theses
Burkholderia glumae is the bacterial pathogen causing bacterial panicle blight disease of rice (BPB). The pathogen, whose growth and pathogenicity is favored by high temperatures, has become a serious threat to rice production around the world possibly due to the current global climate changes. In this study, previously reported avirulent B. glumae strains were characterized in respect to the production of known virulence factors, toxoflavin, lipase and motility, and potential virulence factors, including polygalacturnase and type III secretion system (hypersensitive response). Considerable phenotypic variation was observed among the strains tested. Virulence of the B. glumae strains was closely related to …
Effects Of Environmental Variables And Crop Growth On Development Of Brown Rust Epidemics In Sugarcane, Wilmer Anibal Barrera
Effects Of Environmental Variables And Crop Growth On Development Of Brown Rust Epidemics In Sugarcane, Wilmer Anibal Barrera
LSU Master's Theses
Natural epidemics of brown rust, caused by Puccinia melanocephala, affecting sugarcane were studied to determine the crop and/or environmental factors that affect epidemic onset, severity and eventual decline. Environmental and crop growth variables were monitored along with disease severity in two susceptible cultivars, LCP 85-384 and Ho 95-988, each grown at a different location in Louisiana. During two seasons, correlation and multiple regression analyses identified leaf wetness and temperature as important determinants of disease severity for both cultivars. The results suggested that crop growth variables were not determinants for epidemics. Controlled conditions experiments assessing the interaction of leaf wetness and …
A Comparison Of Soil And Corn Kernel Aspergillus Flavus Populations: Evidence For Niche Specialization, Rebecca Ruth Sweany
A Comparison Of Soil And Corn Kernel Aspergillus Flavus Populations: Evidence For Niche Specialization, Rebecca Ruth Sweany
LSU Master's Theses
Aspergillus flavus is an opportunistic fungal pathogen that infects peanuts, cotton, corn and tree nuts. Aspergillus flavus is a major problem globally due to the production of acutely toxic and carcinogenic aflatoxins. Louisiana climatic conditions lead to annual threats of corn aflatoxin contamination. The purpose of this study was to determine the specific ability of different strains of A. flavus to infect corn. Five soil samples and 10 corn ears were collected from each of seven corn fields throughout Louisiana. In addition, Francis Deville of Monsanto Company collected 7, 6, 2, and 4 soil samples and corn ears from four …
An Assessment Of The Risk Mapping System For The Use Of Managing Loblolly Pine Decline Sites Within Red-Cockaded Woodpecker Habitat, Roger Dale Menard
An Assessment Of The Risk Mapping System For The Use Of Managing Loblolly Pine Decline Sites Within Red-Cockaded Woodpecker Habitat, Roger Dale Menard
LSU Master's Theses
A decline of loblolly pine (Pinus taeda L.), characterized by expanding areas of declining and dead trees, has become prevalent at Fort Benning, Georgia. A 3 year study was conducted to determine the kinds of fungi, insects, and site disturbances associated with this problem. The insects Dendroctonus terebrans, Hylastes salebrosus, Hylastes tenuis, Pachylobius picivorus and Hylobius pales were significantly more abundant in symptomatic than in asymptomatic loblolly pine plots. These root and lower stem-infesting insects consistently carried the fungi Leptographium terebrantis, L. procerum, and L. serpens. Root sampling revealed high levels of root damage and mortality, staining and infection with …
Mechanism Of Intraspecific Toxin Inhibition In Aspergillus Flavus, Changwei Huang
Mechanism Of Intraspecific Toxin Inhibition In Aspergillus Flavus, Changwei Huang
LSU Master's Theses
Atoxigenic Aspergillus flavus was demonstrated by others as a promising biocontrol agent to minimize preharvest aflatoxins in susceptible crops. But the mechanism was unclear. A filter insert-well plate system was used to study the mechanism in lab. There was no inhibition when toxigenic A. flavus isolate 53 and inhibitory atoxigenic isolates were separated by 0.4 µm membrane, approximately 50% inhibition occurred when separated by 12 µm membrane, and complete inhibition occurred when a 74 µm membrane was used. This result suggested that touching or close physical interaction is needed for toxin inhibition and the nutrient competition hypothesis was not supported. …
Pathology And Seedling Nutrition Of Spartina Alterniflora (Smooth Cordgrass), Clark Lane Robertson
Pathology And Seedling Nutrition Of Spartina Alterniflora (Smooth Cordgrass), Clark Lane Robertson
LSU Master's Theses
Transplants of Spartina alterniflora Loisel. (smooth cordgrass, Poaceae) are effective in stabilizing and protecting vulnerable coastal wetlands from erosion. However, the expense and labor associated with propagation and transplanting restrict the widespread use of S. alterniflora in coastal restoration and protection projects. As an alternative, seeding of S. alterniflora by aircraft has been proposed as a more useful and economical approach for revegetating denuded marsh sites. However, a period of stalled growth, which lasts for 12 or more weeks, has been observed in smooth cordgrass seedlings, and this increases their susceptibility to being washed away by inundating tides. This stalled …
Agrobacterium Tumefaciens-Mediated Transformation Of Tobacco (Nicotiana Tabacum L.) Leaf Disks: Evaluation Of The Co-Cultivation Conditions To Increase Beta-Glucuronidase Gene Activity, Sunjung Park
LSU Master's Theses
Agrobacterium tumefaciens-mediated transformation is generally used for genetic transformation of higher plants. Several experimental factors important for the increase of beta-glucuronidase (GUS) reporter gene activity were evaluated in this study using leaf disks of tobacco (Nicotiana tabacum L. cv. Xanthi). We found that co-cultivation temperature at 20C is the most critical factor to obtain the reproducible enhancement of GUS activity. pCAMBIA 1305.01 resulted in higher GUS activity than the other two pCAMBIA vectors 1301 and 1305.02. The highest GUS activity and transformation efficiency were achieved under the following experimental conditions: Agrobacterium tumefaciens strain LBA4404 containing pCAMBIA1305.01 was grown overnight at …
Identification Of Bacterial Pathogens Causing Panicle Blight Of Rice In Louisiana, Xianglong Yuan
Identification Of Bacterial Pathogens Causing Panicle Blight Of Rice In Louisiana, Xianglong Yuan
LSU Master's Theses
Four hundred and two bacterial isolates isolated on the semi-specific S-PG medium from diseased rice tissues showing symptoms of panicle blighting. These isolates were purified using serial dilution in sterile water and replating on S-PG medium. A total of 420 single isolates were obtained. These isolates were subjected to pathogenicity tests on rice (Oryza sative L. cv. Cypress). Based on these tests, 339 isolates were used in BiologTM tests and identified to the species level. Bacterial strains from 39 species in 16 genera were identified, including 52 isolates representing15 Pseudomonas species and 261 isolates representing six Burkholderia species. The remaining …
Sugarcane Seed Response To 2,4-D And Alternative Herbicides For Red Morningglory (Ipomoea Coccinea L.) Control, Jonathan Daniel Siebert
Sugarcane Seed Response To 2,4-D And Alternative Herbicides For Red Morningglory (Ipomoea Coccinea L.) Control, Jonathan Daniel Siebert
LSU Master's Theses
Field studies conducted over two growing seasons evaluated the effect of 2,4-D applied at 1.6 kg ai/ha to LCP 85-384 sugarcane (Saccharum interspecific hybrid) 7, 5, 3, and 1 wk before planting (WBP). Sugarcane was planted in mid-September using both whole stalk and billet (45 cm) seed pieces. When 2,4-D was applied 5 wk or closer to planting, sugarcane shoot emergence and population averaged across planting methods was reduced 5, 7, and 28 wk after planting (WAP) when compared to the nontreated control. Sugarcane height in one of two years was reduced when 2,4-D was applied 5 wk or closer …
A Comparison Of Microbial Communities In Soil With And Without A Sugarcane Cropping, Carolyn Faye Savario
A Comparison Of Microbial Communities In Soil With And Without A Sugarcane Cropping, Carolyn Faye Savario
LSU Master's Theses
Sugarcane (inter-specific hybrids of Saccharum) is grown largely under long-term monoculture production in Louisiana. This can lead to a complex problem termed "yield decline" that results in poor root health and reduced productive capacity of sugarcane. This problem has been documented to be a limiting factor for sugarcane production in diverse regions, including Louisiana, Hawaii, Jamaica, and Australia. Previous work showed that biological factors affect root health and contribute to yield decline. The objectives of this study were to increase our understanding of microbial communities in sugarcane soils, to determine if there are differences in microbial communities associated with sugarcane …
Management Of Imidazolinone-Tolerant (It) Rice In Drill- And Water-Seeded Rice, Kristie J. Pellerin
Management Of Imidazolinone-Tolerant (It) Rice In Drill- And Water-Seeded Rice, Kristie J. Pellerin
LSU Master's Theses
Field studies were conducted over two years in drill- and water-seeded rice to evaluate weed control and crop response with imazethapyr programs. Barnyardgrass [Echinochloa crus-galli (L.) Beauv.] was evaluated with imazethapyr applied alone at various rates and timings. Imazethapyr controlled barnyardgrass 95 to 97% with a soil application at 87 or 70 g/ha fb 53 or 70 g/ha EPOST or LPOST. A single EPOST application of imazethapyr at 140 g/ha controlled barnyardgrass and rice yield was equal to or above those treatments receiving two applications of imazethapyr. Research was also conducted at Crowley, LA and Rayne, LA to evaluate the …