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No description available.

Ragwort (Jacobaea vulgaris syn. Senecio jacobaea), a common weed of pasture and poorly managed land worldwide, is toxic to livestock and horses. There is no fully satisfactory control option available. The aim of the work described in this thesis was to assess the potential of root infecting pathogens to cause disease in ragwort, and to examine the possibility of using them as biological control agents against this weed. Thirty-six root infecting isolates were obtained from ragwort roots, collected from a nationwide postal survey where Pony Club adult leaders were asked to provide samples. Twenty-one of these were identified as Fusarium spp. by morphological identification and tested for the ability to cause disease on aseptically raised ragwort seedlings. Twelve isolates demonstrated virulence towards ragwort when measured by disease score over a 14 day period. These isolates were identified by molecular means using the internal transcribed spacer and translation elongation factor genes, as either Fusarium avenaceum or F. acuminatum while isolates of F. solani, F. redolens, F. cerealis or F. culmorum did not exhibit virulence except one isolate of F. culmorum which was weakly virulent. To investigate the biological control potential of virulent isolates, a representative of F. avenaceum and F. acuminatum plus the one weakly virulent F. culmorum isolate, were tested against plants of agricultural importance in grasslands. Six grasses (crested dogs tail, Cynosurus cristatus; Timothy, Phleum pratense; red fescue Festuca rubra; Italian ryegrass, Lolium multiflorum; and two varieties of perennial ryegrass, L. perenne) were unaffected by inoculation with any of the isolates. There was no significant difference between the symptoms caused by F. avenaceum and F. acuminatum on ragwort, red clover (Trifolium pratense) and white clover (T. repens). F. culmorum was more virulent towards white clover than either red clover or ragwort. This suggests that although high concentrations of pure PA may inhibit fungal growth, the range of other nutrients in the plants can counteract this negative effect.

Digitized by Kansas Correctional Industries

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The work of this dissertation examined the secondary metabolites of several blooms of the marine cyanobacterium Lyngbya collected in Guam and Florida with an emphasis on the isolation and structure elucidation of novel biologically active compounds. The introduction in Chapter One provides a brief history of marine natural products, a description of cyanobacteria and a summary of peptides isolated from Lyngbya collected in the Caribbean. In Chapter Two, a bioassay-guided fractionation of a Floridian collection of Lyngbya polychroa led to the isolation and structural determination of the cytotoxin desacetylmicrocolin B and the known compounds microcolins A and B. The structures were established by nuclear magnetic resonance (NMR) spectroscopic analysis. All three compounds inhibited the growth of cancer cell lines HT-29 and IMR-32 at nanomolar concentrations. Microcolins A and B were found to have little activity in the ecological assay against the marine fungus Dendryphiella salina. Chapter Three describes the isolation and structure elucidation of the glycosidic, acyl proline derivative tumonoic acid J from a sample Lyngbya sp. collected in Guam. The planar structure was determined by 1D and 2D NMR spectroscopy in conjunction with high resolution-mass spectrometry (HR-MS) data. Tumonoic acid J showed moderate activity in the ecological assay against the marine fungus D. salina. In Chapter Four, NMR-guided fractionation of a Floridian sample of Lyngbya majuscula led to the isolation of two novel cyclic peptides porpoisamides A and B. The planar structures were determined by 1D and 2D NMR spectroscopy with HR-MS data. The absolute configurations of these two compounds were defined through chiral chromatographic methods and derivatization techniques. / The porpoisamides showed only moderate activity in cytotoxicity assays against cancer cell lines HCT-116 and U2OS. Finally, Chapter Five examines a potential ecological role of compounds isolated from marine cyanobacte ria. These secondary metabolites may function as chemical defenses against competing microorganisms within marine environments. Compounds isolated from cyanobacteria were tested for anti-fungal activity against the saprophytic marine fungus D. salina. Three of the six compounds tested produced inhibitory activity at or below their natural concentration. / by Theresa Meickle. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

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No description available.

No description available.

This thesis reports laboratory and field investigations on the aspects of biology of the Stethorus vagans, an Australian ladybird that feeds on all stages of two-spotted mite, Tetranychus urticae. Aspects of the biology of S. vagans were studied in the laboratory at constant and fluctuating temperatures. They regularly fed on all stages of T. urticae and there was no significant difference in male and female longevity at different temperatures. For field studies potted French bean plants infested with T. urticae were exposed in the field. Adult S. vagans was found to consume a range of alternative prey if the primary host was not available, but only one of the alternative hosts had the potential to support reproduction. Time partitioning behaviour and prey consumption rates were assessed, and how S. vagans located their prey was investigated. S. vagans exhibited many of the attributes of an effective biological control agent such as high reproductive level, location of prey at low levels, reproduction at low densities, and ability to feed on alternative hosts. It is concluded that S. vagans has a number of characteristics likely make them useful as a natural enemy of T. urticae / Doctor of Philosophy (PhD)