Thesis (Ph.D.(Plant Pathology)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 57-64).

There are numerous examples of how exotic insect pests and pathogens have altered the dominance of native tree species and the ecological processes and function related to those species. While targeted species may persist in a functionally altered state via vegetative sprouting, the widespread decimation of a species can have dramatic direct and indirect consequences for organisms in multiple trophic levels. Devastation due to alien insect herbivores poses the greatest threat to native insect larvae that specialize on the impacted host species. The loss of pollinators whose larvae feed on impacted species and provide services for native plants may also be a serious but yet undocumented indirect threat of these exotic invasions. The disruption of mutualistic relationships between native species will have negative consequences for those species and could potentially benefit exotic species. In the southeastern US, laurel wilt disease (LWD) is impacting numerous species in the Lauraceae family, with the majority of cases observed on Persea borbonia, a common sub-canopy tree found in many Coastal Plain habitats. This species is also known to be the primary larval host of the palamedes swallowtail (Papilio palamedes). While infection rates and crown dieback are catastrophically high (>90%), basal resprouting is a common response in P. borbonia. The exotic Cinnamomum camphora is the only Lauraceae species that has shown resistance to LWD and could benefit from opportunities to replace P. borbonia and other Lauraceae species threatened by LWD. The primary objectives of this study were four fold: 1) to quantify P. borbonia sprouting responses in the field and greenhouse and determine the effect of P. borbonia removal on the composition and abundance of woody and herbaceous plant species in the understory layer, 2) to test the relative suitability of C. camphora as an alternative larval host for P. palamedes, 3) to determine the reliance of the Platanthera ciliaris on P. palamedes for successful pollination and the relative availability of alternative long-tongued pollinators, and 4) to forecast how disease-induced shifts in the relative abundance of native (P. borbonia) and exotic (C. camphora) fruit may alter patterns of consumption and subsequent dispersal of C. camphora by birds. The field component (Grand Bay National Estuarine Research Reserve (GBNERR), Jackson County, MS) of chapter two involved the removal of P. borbonia main stems to mimic the impacts of LWD which resulted in a significant increase (~50%) in light transmission. All treated individuals produced sprouts and the size and number of sprouts was positively related to initial tree size. Following the removal of P. borbonia from treatment plots, Ilex vomitoria showed the greatest increase in basal area after two years. Both woody seedlings and herbaceous plants showed no significant trends in composition and/or abundance over time. In the greenhouse (Southern Illinois University, Carbondale, IL), the stem and leaf biomass of vegetative sprouts was significantly greater in a high-nutrient treatment. Light treatments had no effect on sprout production. Results from chapter two suggest that the loss of P. borbonia from the canopy layer may have little direct effect on plant community dynamics. In addition, I found that sprout production is vigorous in P. borbonia and the capacity to persist and tolerate future disturbances may be enhanced on more nutrient-rich sites. In chapter three, I used laboratory experiments and field observations to compare larval performance and adult female preference of P. palamedes between C. camphora and P. borbonia foliage. My results indicate moderate survivorship on C. camphora (46%) compared to P. borbonia (87%) and there were no differences in first and fourth instar growth rates between treatments. Fourth instars consumed less C. camphora foliage than P. borbonia, but metabolic efficiency did not differ between treatments. In the field and laboratory, I found no oviposition preference for C. camphora relative to P. borbonia. While females laid eggs on C. camphora during laboratory trials, the same number of eggs was also laid on inanimate objects. I conclude that C. camphora is suitable for larval development but host-switching to this species by P. palamedes will be primarily constrained by oviposition behaviors. In chapter four, I monitored pollinator visitation and measured nectar spur lengths of P. ciliaris flowers and proboscis lengths of its floral visitors (at GBNERR). Papilio palamedes was the primary visitor (44 visits) but Phoebis sennae was also observed (4 visits). There were no significant differences among P. ciliaris nectar spurlength and the proboscis lengths of P. palamedes and P. sennae. Fruit set was 55 ± 10.8% with access to pollinators and 0% on bagged inflorescences (pollinators excluded). Although I found a positive relationship between visitation and inflorescence size, there was no such pattern in fruit set, indicating that fruit set was not limited by pollinator visitation within the range of visitation rates I observed. Phoebis sennae may provide supplemental pollination service but is likely constrained by habitat preferences that do not always overlap with those of P. cilaris. Although additional observations are needed, my results suggest that expected LWD-induced declines of P. palamedes will threaten the reproductive success and persistence of P. ciliaris populations. In chapter five, I investigated redundancy between C. camphora and P. borbonia with respect to fruit characteristics (physical and chemical) and selectivity by frugivorous birds (at GBNERR). Across two winter survey periods I observed fruit removal from artificial infructescences. I manipulated background species upon which displays were hung (Myrica cerifera and Triadica sebifera) and the accessibility of the displays. Using motion-activated cameras I confirmed foraging bouts on both P. borbonia and C. camphora fruits by three bird species (Dumetella carolinensis, Turdus migratorius, and Catharus guttatus). There was no significant difference in selectivity between fruit types during year one of my surveys but there was a significant preference for C. camphora in year two, which coincided with significantly lower mean daily temperatures. Background tree species and accessibility had no apparent effect on fruit preference. Total polyphenols and pulp:seed ratio were significantly higher in C. camphora fruit. I conclude that the fruits of C. camphora and P. borbonia represent nearly substitutable resources for native birds. However, native species may prefer C. camphora fruit in times of energetic stress. The decline of P. borbonia will likely increase the consumption and dispersal of C. camphora fruits. Additional studies are required to determine if such changes could ultimately increase the distribution and abundance of this exotic species. Combined, the chapters of this dissertation present substantial empirical evidence for the potential multi-trophic level impacts of an exotic plant disease. While it remains unclear how dramatic these impacts will be, the approach used here is vital for understanding and mitigating the long-term ecological effects of species/disease invasions.

Orientador: Antonio Carlos Maringoni / Banca: Marcelo Agenor Pavan / Banca: Margarida Fumiko Ito / Resumo: murcha-de-curtobacterium é uma doença que acarreta sérios prejuízos na produção do feijoeiro no País e seu agente causal, a bactéria Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), é transmitido por sementes. São indicados o uso de sementes livres do patógeno, rotação de culturas e cultivares resistentes para o manejo da doença em campo. Foi realizada a avaliação da transmissão de Cff via sementes de feijão, em três ensaios, em seis cultivares de feijoeiro (IAC Carioca, IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã, IAC Carioca Tybatã e Pérola). Essas cultivares foram inoculadas com um isolado de Cff via punção no caule e os sintomas da doença foram avaliados com uma escala de notas. A análise da transmissão da bactéria pelas sementes foi realizada nos três ensaios, em 500 sementes das cultivares IAC Carioca, IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã, IAC Carioca Tybatã e para a cultivar Pérola, foram analisadas 46, 155 e 87 sementes respectivamente no primeiro, segundo e terceiro ensaios. As sementes foram maceradas individualmente em água destilada e esterilizada, incubadas por 24 horas e a suspensão obtida foi semeada em placas de Petri contendo meio de cultura semi-seletivo para Cff e incubadas à temperarura de 28 a 30 oC, durante 96 a 120 horas. As colônias com características típicas de Cff, comparadas com um isolado puro padrão, foram purificadas em meio NSA + NaCl 7%, realizados testes de coloração diferencial de Gram, KOH e patogenicidade. Os isolados primeiro e segundo ensaios foram caracterizados por Microlog2TM e os do terceiro, via PCR. Os resultados mostraram que as cultivares de feijoeiro IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã e IAC Carioca Tybatã apresentaram baixos índices de severidade da doença, indicando resistência à murcha-de-curtobacterium, já as cultivares Pérola e IAC ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Bean bacterial wilt is a disease that cause serious losses to the Brazilian dry beans production and its causal agent, Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), is seedtransmitted. The use of pathogen-free seeds, culture rotation and resistant cultivars are recommended for disease handling on the field. The evaluation of Cff transmission by seeds was carried out by conducting three assays in six common beans cultivars (IAC Carioca, IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã, IAC Carioca Tybatã and Pérola). These cultivars were inoculated with a Cff isolate via a puncture on the stem and the desease symptoms were evaluated with severity index. The analysis of bacterial seed transmission was carried out in all of the three assays in 500 seeds of cultivars IAC Carioca, IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã and IAC Carioca Tybatã. For cultivar Pérola, 46; 155 and 87 seeds were analyzed respectively on the first, second and third assays. Seeds were individually macerated in distilled and sterilized water for 24 hours and the suspension thus obtained was sown on Petri dishes with a Cff semi-selective medium and incubated at 28 - 30 °C from 96 to 120 h. Colonies with typical Cff characteristics as compared with a standard pure isolate were purified in a NSA + NaCl 7% medium, Gram, KOH and pathogenicity tests being carried out. The isolates from the first and second assays were characterized by Microlog2TM and those of the third one by PCR. Results showed that common beans cultivars IAC Carioca Aruã, IAC Carioca Akytã, IAC Carioca Pyatã and IAC Carioca Tybatã presented... (Complete abstract click electronic access below) / Mestre

Ph.D. (Biochemistry) / Please refer to full text to view abstract

M.Sc. / A phytotoxic protein-lipopolysaccharide complex (PLPC) was isolated from 7 day old culture filtrates of Verticillium dahliae. The complex was purified to electrophoretic homogeneily by means of acetone precipitation, gel, chromatography and preparative agarose electrophoresis with a yield of 4.5 mg PLPC per litre culture filtrate ...

In growing alfalfa it is important to obtain a good initial stand. However, it is difficult to predict the exact amount of seed necessary to insure a good stand.

Over the past decade, the Eastern Shore of Virginia (ESV) has been implicated in at least four outbreaks of Salmonellosis associated with tomato all originating from the same strain, Salmonella enterica serovar Newport.  In addition to S. Newport contamination, the devastating plant disease, bacterial wilt, caused by the phytopathogen Ralstonia solanacearum threatens the sustainability of ESV tomato production.  Bacterial wilt is present in most ESV tomato fields and causes devastating yield losses each year.  Due to the ESV\'s endemic population of R. solanacearum and S. Newport, the relationship between the two pathogens is of interest and has never been investigated.  Two separate studies were conducted to assess the relationship between these two bacteria.  One study consisted of a series of greenhouse trials that involved root-dip inoculations of tomato plants with one of four treatments: 1) S. Newport, 2) R. solanacearum, 3) a co-inoculation of S. Newport + R. solanacearum, and 4) a control group with no inoculation. Leaf, stem, and fruit samples were collected from the plants and S. enterica presence from the internal tissues was observed.  S. enterica was recovered from a low percentage of fruit and leaf samples.  There were significantly more stem samples from plants co-inoculated with S. Newport + R. solanacearum positive for S. enterica (17.46%) than from other treatments.  Another study examined the relationship between the two bacteria via vacuum infiltration inoculations of tomato fruit collected from commercial production fields on the ESV with S. Newport.  Tomato fruit were collected from plants expressing symptoms of bacterial wilt (symptomatic) and plants not expressing bacterial wilt symptoms (asymptomatic).  After fruit infiltration with S. Newport, recovery concentration of S. enterica from internal tissues was measured.  S. enterica populations were greater in fruit originating from asymptomatic (5.15 log CFU/g) versus symptomatic (4.91 log CFU/g) plants across five studies.  Fruit collected from asymptomatic plants had a significantly higher internal pH (4.60) than fruit collected from symptomatic plants (4.37).  These results suggest that R. solanacearum can influence S. enterica survival and transportation throughout the internal tissues of tomato plants as well as the influence internal tomato fruit pH, which could potentially impact S. Newport survival in the fruit. / Master of Science in Life Sciences

Several native species of Lauraceae (e.g. sassafras) in the southeastern United States are being eradicated by laurel wilt disease. Laurel wilt is caused by a highly invasive and cryptic ambrosia beetle, Xyleborus glabratus, and its fungal symbiont. The symbiont pathogen is spread during colonization of native Lauraceae. Xyleborus glabratus and the pathogen are remarkably effective at colonizing and killing healthy populations of Lauraceae in a brief time period. Control methods have been unable to slow the spread of laurel wilt disease and X. glabratus populations have been spreading into northern latitudes. Presently, cold temperatures may be the only factor limiting establishment of the beetle in interior populations of sassafras. Empirically derived physiological data from this study were combined with climatic, microhabitat, and host data to model the invasive potential/hazard rate of X. glabratus and laurel wilt in sassafras forests of the United States. Sharing this model data will help land managers, forest health specialists, urban foresters, and landowners make informed proactive management decisions regarding laurel wilt disease.

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