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A Systematic Study Of Xylella Fastidiosa Strains Isolated From Pecan, Grapevine, Oleander, And Sycamore In Louisiana, Rebecca Ann Melanson Jan 2011

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 …


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 Jan 2011

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 …


Comparative Proteome And Qpcr Analysis Of The Sugarcane Reaction To Leaf Scald Caused By Xanthomonas Albilineans, Freddy Fernando Garces-Obando Jan 2011

Comparative Proteome And Qpcr Analysis Of The Sugarcane Reaction To Leaf Scald Caused By Xanthomonas Albilineans, Freddy Fernando Garces-Obando

LSU Doctoral Dissertations

Leaf scald is an important disease of sugarcane caused by Xanthomonas albilineans (Xa). Leaf scald is controlled by the development and planting of resistant cultivars. However, erratic symptom expression makes conventional screening for resistance difficult. In addition, the mechanisms of resistance to leaf scald are not completely understood. Real-time, quantitative polymerase-chain-reaction (qPCR) assays were developed utilizing SYBR Green for a highly sensitive detection method or a TaqMan probe to quantify Xa populations in infected plants. Xa populations detected by qPCR followed similar trends to disease severity ratings and vascular infection results for two resistant and two susceptible cultivars under greenhouse …


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 Jan 2011

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. …


Simplicillium Lanosoniveum, A Mycoparasite Of Phakopsora Pachyrhizi And Its Use As A Biological Control Agent, Nicole A. Ward Jan 2011

Simplicillium Lanosoniveum, A Mycoparasite Of Phakopsora Pachyrhizi And Its Use As A Biological Control Agent, Nicole A. Ward

LSU Doctoral Dissertations

In 2007, a filamentous fungus was recovered from sori of soybean rust (SBR), caused by Phakopsora pachyrhizi, collected from Louisiana and Florida. This fungus was identified as Simplicillium lanosoniveum on the basis of ITS sequence data and morphological traits. Simplicillium lanosoniveum was found coiling within sori and around urediniospores and showed a trophic attraction to rust sori, extending from sorus to sorus. In co-inoculated soybean leaves, the fungus did not grow or establish on leaf surfaces until sori erupted. Similarly, S. lanosoniveum colonized within 3 days and sporulated within 4 days on leaves showing disease symptoms. In field studies, when …


Optimization Of Heat-Stable Protein Extraction In Recalcitrant Spartina Alterniflora, Yi Wang Jan 2011

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 …