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Plant Sciences

Theses/Dissertations

Louisiana State University

Biocontrol

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Investigations Into Aspergillus Flavus Infection Of Corn And Regulation Of Aflatoxin Production By Volatiles And Biocontrol Strains, Rebecca R. Sweany Jan 2019

Investigations Into Aspergillus Flavus Infection Of Corn And Regulation Of Aflatoxin Production By Volatiles And Biocontrol Strains, Rebecca R. Sweany

LSU Doctoral Dissertations

Aspergillus flavus is an ascomycete fungus impacting agriculture, public and environmental health due to production of acutely-toxic, carcinogenic aflatoxins in oil seed crops, especially corn in Louisiana, and lung infections of immunocompromised patients resulting in a leading cause of AIDS patients’ deaths globally. The most effective aflatoxin mitigation strategy, biocontrol by atoxigenic A. flavus presents several concerns including: dissemination of a human pathogen, possible sexual reproduction and reliance on precise environmental conditions. Several aspects of A. flavus biology were investigated to potentially improve treatments. Studies investigated how genotypically diverse members within the A. flavus population interact with other population members …


Genetics And Genomics Studies Of Rice Disease Resistance And Development Of Alternative Disease Management Methods For Bacterial Panicle Blight And Sheath Blight, Bishnu Kumar Shrestha Jan 2014

Genetics And Genomics Studies Of Rice Disease Resistance And Development Of Alternative Disease Management Methods For Bacterial Panicle Blight And Sheath Blight, Bishnu Kumar Shrestha

LSU Doctoral Dissertations

Bacterial panicle blight (BPB) and sheath blight (SB), caused by the bacteria Burkholderia glumae and B. gladioli, and the fungus Rhizoctonia solani, respectively, are two major rice diseases in southern rice growing regions of US. No completely resistant rice cultivars have been identified for these diseases. However, a medium-grain cultivar, Jupiter, showed partial resistance to BPB. In order to understand the mechanisms of rice resistance against BPB and SB, rice genetics and genomics studies have been conducted. Alternative methods to suppress BPB and SB were also studied. Broad-sense heritability and correlations were calculated for the traits, BPB and SB disease …


Characterization Of A Σ54-Dependent Response Regulator, Tepr, In The Rice-Pathogenic Bacterium Burkholderia Glumae And Development Of Biocontrol Strategies For Bacterial Panicle Blight Of Rice, Surendra Osti Jan 2014

Characterization Of A Σ54-Dependent Response Regulator, Tepr, In The Rice-Pathogenic Bacterium Burkholderia Glumae And Development Of Biocontrol Strategies For Bacterial Panicle Blight Of Rice, Surendra Osti

LSU Master's Theses

Bacterial panicle blight, caused by Burkholderia glumae, is a major bacterial disease of rice in Louisiana. This bacterium contains several virulence factors required for disease development such as toxoflavin, lipase and flagella. In a genome-wide search for regulatory factors related to the virulence of B. glumae, tepR was identified as a negative regulator for toxoflavin production and found to encode a sigma 54-dependent response regulator. TepR is homologous to LuxO, a quorum-sensing signaling component of Vibrio spp. A markerless tepR deletion mutant of B. glumae 336gr-1, LSUPB401, produced more toxoflavin and showed higher lipase and protease activities compared to the …


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 …