Dissertations / Theses on the topic 'Inoculum source'

Rhizoctonia solani inoculum can be present either as soil- or tuber-borne sclerotia or hyphae. Although both inoculum sources play a role in disease development, it is not clear which of the two is more important. Successive cultivation of potato crops increases R. solani soil inoculum load resulting in an escalation in disease incidence and severity. The use of tolerant cultivars, however, can effectively reduce inoculum levels thereby decreasing disease intensity. Four pot trials were conducted; the objective of the first two pot trials was to determine the effect of tuber and soil-borne inoculum and stolon inoculations on disease development in sandy and clay loam soils. The second two pot trials were aimed at determining susceptibility levels of five cultivars. Two field trials were planted over two growing seasons in the same soils, using three inoculum levels. Results from the pot trials showed that tubers harvested from inoculated sandy soils developed significantly more disease than those harvested from clay loam soils. Of the three inoculum sources, stolon inoculation and seed-borne inoculum resulted in significantly more disease on progeny tubers than those from R. solani spiked soils. Although none of the cultivars proved to be tolerant to R. solani, BP1 was less susceptible to R. solani at temperatures between 21-26oC. More severe disease symptoms were observed under cooler temperatures on all cultivars. Results from the field trial showed the cultivation of potatoes in the same soil over two growing seasons resulted in an increase in diseased (black scurf) tubers. Furthermore, black scurf was most severe on tubers from soils infested with the highest concentration of inoculum. There were significant disease severity differences, with initial soil inoculum levels being directly proportional to final disease severity. Future studies in South Africa should focus on investigating the genetic composition of various cultivars; the effect of soil type and pH on the pathogenicity of R. solani and the use of molecular diagnostic tools to detect and quantify R. solani in soils.
Dissertation (MSc)--University of Pretoria, 2012.
Microbiology and Plant Pathology
unrestricted

For psychrophilic anaerobic digestion systems, natural biota may provide sources of already adapted inoculum to reduce reactor start up time. The objective of the research was to test the inoculum potential of the microbial populations found in eight river sediments from the Montreal region, Canada, for the psychrophilic anaerobic digestion of swine manure. Also, to develop a simple theoretical method for quantification of acetoclastic methanogens in natural biota and validate using QRT-PCR technique. The anaerobic methanogenic populations of the sediments was quantified and characterized at 22 °C with specific methanogenic activity tests (SMA) using acetate and H2/CO2 as substrates. Then, biochemical methane potential (BMP) tests were conducted for 190 days at 10 °C using as substrate sterile swine manure, and as inoculums, the sediment with the highest methanogenic activity, fresh swine manure and sludge from an agro-food anaerobic mesophilic digester (AD sludge).
All eight sediments demonstrated pseudo-lag phases during the acetate SMA because of the low initial microbial populations. A visually significant correlation was observed between mgd.wt.cells/g sediment obtained from the predicted model and cell number/g sediment from the QRT-PCR results. During the H2/CO2 SMA, most sediments exhibited homoacetogenic activity out-competing that of the hydrogenotrophic methanogens. As compared to the most active sediment and swine manure and AD sludge inoculum presented approximately seven times more methanogenic activity at psychrophilic conditions. It also yielded 334 ml CH4/g CODin, which is almost twice as that of the active sediment. Further tests are required to optimize the process conditions, (i.e. loading rates, pH, etc.) in order keep the activity on its maximum.
Certaines biotes naturelles seraient en mesure de fournir aux systèmes de digestion anaérobie avec organismes psychrophiles des sources d'inoculum pré adaptés, réduisant ainsi le temps de démarrage du réacteur. L'objectif de cette étude fut d'évaluer le potentiel comme inoculum de populations microbiennes provenant de huit dépôts sédimentaires fluviaux de la région Montréalaise, pour la digestion anaérobie avec psychrophiles du lisier de porc. Il s'agirait aussi de développer une méthode théorique de base pour quantifier les méthanogènes acétoclastiques dans les biotes naturelles, et de la valider en utilisant une technique de transcription inverse suivie d'une PCR quantitatif en temps réel (QRT-PCR). Les populations anaérobies méthaniques des sédiments furent quantifiés et caractérisés à 22 °C grâce à des tests spécifiques d'activité méthanigène (SAM), utilisant l'acétate ou le H2/CO2 comme substrats. Des tests pour évaluer la production potentielle de méthane par voie biochimique (PPMB) se sont déroulés à 10 °C sur une durée de 190 jours, utilisant du lisier de porc stérile comme substrat, et comme inoculum soit (i) les sédiments ayant l'activité methanigène la plus élevée, (ii) du lisier de porc frais, ou (iii) de la boue de digesteur anaérobie (boue DA) de matières agroalimentaires.
Étant donné leur basses population microbiennes initiales, tous les sédiments présentèrent une pseudo phase de latence durant le test SAM avec l'acétate. Une corrélation visuelle significative fut notée entre le poids sec de cellules par grammes de sédiment (mg/g) prédite par la méthode théorique et celle obtenue par QRT-PCR. Lors du test SAM avec H2/CO2, la plupart des sédiments présentèrent une activité homoacétogène dépassant celle des méthanogènes hydrogènotrophes. Comparé au lisier de porc et à la boue DA, sous des conditions psychrophyliques le sédiment le plus actif a produit sept fois plus de CH4 par masse d'ATP. Aussi produisit-elle 334 ml CH4/g CODin, près de deux fois le rendement du sédiment actif. D'autres tests seront nécessaires pour optimiser les conditions opératoires (i.e., taux de charge, pH, etc.) afin de maintenir l'activité à un maximum.

The incidence and damage caused by the fungus Claviceps gigantea has increased considerably in the Toluca Valley region. It has been reported in fields of susceptible maize hybrids at altitudes from 2,000 to 2,800 masl, especially in plots under high productivity programs. The objective of this study was to identify the source of the inoculum leading to the expression of Claviceps gigantea in the Faisán® hybrid, evaluating different concentrations of ascospores and microconidia (500,000; 250,000; 100,000 and 50,000). The study consisted of two stages. The first was performed in the laboratory, to obtain solutions at the different experimental doses, and the second was performed in the field, where plants that were considered ideal for inoculation were inoculated using the injection technique. For each inoculum type and concentration, 5mL were injected per plant. The results showed that the source of inoculum was ascospores, and 100,000 was the dose that led to the highest incidence and most severe degree of horse’s tooth; the incidence of ears affected increased by 50%, and sclerosis formed by 40 days. Thus, this type of spore demonstrated an ability to generate a new inoculum, reproductive structures, and/or spores in a shorter time period.

In recent years two new diseases, brown spot and black pit, have been observed on potatoes in South Africa. Brown spot symptoms appear on the foliage as small brown lesions, whereas black pit symptoms appear on the tubers as small dark sunken lesions. In this study the causal organism of brown spot and black pit of potatoes in South Africa was determined. During initial isolation, one fungus and two bacteria were isolated, which were included in the trial. Only the treatments where the fungal isolate was used in inoculation resulted in the development of brown spot lesions. The causal organism of brown spot and black pit were identified as Alternaria alternata which is consistent with other research. To better understand the spread of Alternaria alternata between the plants and/or tubers a pot trial was conducted. It was observed that when planting an inoculated seed tuber brown spot may develop on foliage. But the daughter tubers harvested from plants infected with A. alternata will not necessarily develop black pit. Daughter tubers are most likely infected by A. alternata during harvesting and black pit lesions develop in high humidity in storage. Cultivar resistance is one of the most important measures in controlling plant diseases. Cultivar susceptibility of thirteen South African potato cultivars (Avalanche, Buffelspoort, BP1, Fabula, Fianna, Frodo, Hertha, Labadia, Lanorma, Mondial, Pentland Dell, Up-To-Date and Van Der Plank) was evaluated. Pot trials showed that all the evaluated cultivars are susceptible to infection by Alternaria alternata. Various crops (tomatoes, cabbage, mustard, wheat, oats, tobacco and maize) were assessed to determine the host range of Alternaria alternata (potato pathotype) in rotation crops in South Africa potato growing regions. Of the crops evaluated, the pathogen was able to infect only tomato crops. Only wheat, maize and oats can safely be used in the crop rotation in South Africa, as various potato pathogens attack cabbage, mustard and tobacco plants. This study will lead to a better understanding of brown spot and black pit diseases of potatoes in South Africa and globally. The study emphasise the need for further research which will help to reduce brown spot and black pit diseases of potato.
Dissertation (MSc Agric)--University of Pretoria, 2013.
gm2014
Microbiology and Plant Pathology
unrestricted

Filamentous bulking in activated sludge treatment plants is a worldwide problem. Understanding the growth requirements of specific filamentous organisms will allow the development of better control strategies for bulking. In this study, the short term effects of eight carbon sources and three inoculum sources on the growth of filamentous bacteria were tested. Three lab scale sequencing batch reactors (SBR) were operated. Microscopic (Gram and Neisser staining) and molecular methods (Denaturing Gradient Gel Electrophoresis [DGGE], Fluorescent in Situ Hybridization [FISH]) were used to track the microbial population changes in the reactors. Sludge volume index (SVI) measurements were used to monitor bulking in the reactors. DGGE and sequencing results indicated the presence of the filamentous bacteria Sphaerotilus natans and Thiothrix. S. natans grew in glucose-, acetate-, and sucrose-fed reactors, regardless of the inoculum source. It also grew in propionate- and pyruvate-fed reactors inoculated with the sludge from the Neuse River Wastewater Treatment Plant (WWTP). Thiothrix was detected in propionate- and pyruvate-fed reactors inoculated with sludge from the South Cary WWTP, and in glucose- and acetate-fed inoculated with the sludge from the Neuse River WWTP inoculated reactors. In addition to these two filaments, Gram and Neisser staining indicated the presence of Nostocoida limicola in Neuse River WWTP inoculated reactors. The presence of S. natans and T. nivea was confirmed with FISH. SVI measurements were consistent with the level of bulking, showing an increase as the number of filaments in the reactors increased. This study confirmed that readily biodegradable substrates favored the growth of S. natans, T. nivea and, N. limicola in activated sludge. The simultaneous use of microscopic and molecular tools provided the information above with one method compensating for the other method?s biases.

Fusarium head blight (FHB) is one of the most economically important diseases of small grains and continues to impact crops when environmental conditions are favorable to Gibberella zeae (Fusarium graminearum), the causal agent of the disease. Corn residues are considered to be primary sources of inoculum for epidemics of FHB. Therefore, knowledge of the movement of Gibberella zeae from a local source of infested corn residue is critical to the management of FHB in wheat and barley. Previous research made significant progress in defining the spatial dissemination of inoculum sources of G. zeae within agricultural fields, but was unable to clearly distinguish between within-field and background sources. Using amplified fragment length polymorphism, released clones of G. zeae were tracked within wheat and barley fields. This strategy allowed the distinction between the contributions of released clones to FHB, compared to that of background inocula. Corn residue infested with clones of G. zeae was placed into small replicated plots in winter wheat fields in New York and Virginia in 2007 and 2008 and wheat spikes were collected at 0, 3, 6, and â ¥24 m from the inoculum sources. Recovery of released clones decreased an average of 90% between 3 and 6 m from inoculum sources. Various amounts of corn residue infested with a single clone of G. zeae were placed into small replicated plots in winter wheat and barley fields in Virginia from 2008 to 2010. The use of minimal or conventional tillage and a moderately resistant cultivar of wheat or barley may reduce the contribution of within-field inocula to FHB; however, environmental conditions play an important role in the effectiveness of these management strategies. With the increase of corn production due to incentives for ethanol-based fuel, overwintering sites for G. zeae on corn residue are likely to increase. Our work contributes to an increased understanding of the influence of overwintered corn residue to FHB which will also direct future research on how to reduce the inoculum potential from within-field sources.
Ph. D.

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Ralstonia spp. são conhecidas por causar murcha bacteriana em várias plantas de interesse econômico. O patógeno possui alta variabilidade genética, ampla variedade de hospedeiros e pode sobreviver no solo mesmo na ausência de hospedeiros. A compreensão das potenciais fontes de inóculo, que contribuem para a variabilidade genética no centro de origem do patógeno é interessante para o manejo da doença. O papel dos rios, plantas daninhas e da população nativa de Ralstonia spp. em áreas de vegetação natural no desenvolvimento de epidemias de murcha bacteriana é pouco compreendido. A variabilidade genética entre cepas de Ralstonia spp. em uma região onde a doença é endêmica pode elucidar a contribuição dos meios de dispersão e fatores associados à sobrevivência. No presente estudo, a detecção de Ralstonia spp. em rios de diferentes biomas do Brasil revelou o potencial destes recursos naturais para dispersar o patógeno. As plantas invasoras mostraram ser importantes reservatórios de ambas as espécies de Ralstonia que ocorrem no Brasil e colaboram para sua sobrevivência. Métodos de detecção não foram sensíveis para confirmar a presença de Ralstonia spp. em amostras de solo de áreas sem ocorrência de murcha bacteriana. Quando se analisaram 204 isolados de R. solanacearum e 60 isolados de R. pseudosolanacearum obtidos do município de Coimbra, Minas Gerais, constatou-se haver baixa variabilidade genotípica e clonalidade. Nenhuma estruturação foi observada para as regiões do município, mas a composição genotípica variou entre os anos amostrados. Para o controle alternativo da murcha bacteriana, cinco fagos pertencentes à família Siphoviridae, ordem Caudovirales, foram isolados em amostras de solo. A análise molecular e a gama de hospedeiros com diferentes isolados de Ralstonia spp., representando o Brasil, revelaram diferenças entre os vírus. Adicionalmente, houve diferenças quanto à gama de hospedeiros quando os cinco fagos foram expostos a 24 isolados de Ralstonia spp. Os fagos não foram capazes de prevenir a infecção e controlar o número de células de Ralstonia spp. no solo. Outros métodos de aplicação são necessários para avaliar a eficiência dos fagos no controle da murcha bacteriana.
Ralstonia spp. are known to cause bacterial wilt in several plants of economic interest. The pathogen has high genetic variability, wide host range and can survive in the soil even in the absence of hosts. Understanding potential inoculum sources that contribute to genetic variability in the center of origin is interesting to the management of the disease. The importance of rivers, weeds and native population of Ralstonia spp. in areas of natural vegetation in the development of epidemics of bacterial wilt is poorly understood. Genetic variability among strains of Ralstonia spp. in a local region where the disease is endemic can elucidate the contribution of the means of dispersal and factors of survival. In the present study, the detection of Ralstonia spp. was attempted in water of rivers of different biomes of Brazil and revealed the potential of these natural resources to disperse the pathogen. Weeds were important reservoirs of both species of Ralstonia that occur in Brazil, and collaborate to their survival. Methods of detection were not sensitive to confirm the presence of Ralstonia spp. in soil samples from areas without the occurrence of bacterial wilt. The genetic variability of 204 strains of R. solanacearum and 60 strains of R. pseudosolanacearum from the municipality of Coimbra, Minas Gerais, was low and there was evidence of clonality in the population. The population was not genetically structured according to the geographic region in the municipality, however the genotypic composition varied in time. To assess an alternative measure to control bacterial wilt, five phages were isolated. All phages belong to the Siphoviridae family, Caudovirales order. Molecular analysis and host range with different R. solanacearum strains revealed differences among the viruses. There were differences in the host range when the five phages were exposed to 24 Ralstonia spp. strains. The phages were not able to prevent tomato infection and control the number of cells of Ralstonia spp. in the soil. Other methods of application are necessary to evaluate the efficiency of the phages to control of bacterial wilt.

Las enfermedades de la madera se encuentran entre las patologías más dañinas que afectan al cultivo de la vid. El pie negro es una de las más destacadas, afectando a las plantas en vivero y en plantaciones jóvenes. Los agentes causales están incluidos dentro de los géneros Campylocarpon, ¿Cylindrocarpon¿, Cylindrocladiella e Ilyonectria. Éstos se caracterizan por ser habitantes del suelo y, se ha demostrado que permanecen en él, infectando al material de propagación cultivado en campos de vivero. La presencia de hongos asociados al pie negro en vivero, así como sus fuentes potenciales de inóculo en suelos de vivero y de viñedos comerciales, no han sido nunca estudiados en España. En este sentido, el objetivo de esta Tesis ha sido estudiar la epidemiología de hongos que causan el pie negro de la vid en España. En primer lugar, las distintas fases del proceso viverístico se evaluaron como fuentes potenciales de inóculo de estos patógenos. Se tomaron muestras en cuatro fases del proceso de propagación de las que se extrajo el ADN, detectándose las especies causantes del pie negro de la vid mediante multiplex, nested PCR. En las fases estudiadas se detectaron I. liriodendri y el complejo I. macrodidyma. También se estudió la detección de especies de Ilyonectria en material de propagación de vid, antes y después de la fase de enraizamiento en campos de vivero, mediante técnicas de aislamiento y multiplex, nested PCR. Este estudio confirmó que el número de plantas infectadas con estos patógenos aumenta durante el proceso de enraizamiento en campos de vivero. Ilyonectria torresensis fue la única especie aislada de las plantas tras la inducción del callo. Sin embargo, las especies I. liriodendri, I. novozelandica e I. torresensis se aislaron frecuentemente tras el período de cultivo en campos de vivero. Respecto a la detección molecular, se detectaron un número elevado de muestras positivas en planta tras la inducción del callo y después del proceso de enraizamiento. Mediante el uso de cuatro técnicas diferentes, aislamiento fúngico a partir de raíces de plántulas de vid utilizadas como plantas trampa, aislamiento a partir de raíces de malas hierbas, multiplex, nested PCR y qPCR, se estudió el suelo de campos de plantas madre como fuente de inóculo de estos patógenos. De las raíces de plantas trampa se aislaron las especies I. alcacerensis, I. macrodidyma, I. novozelandica e I. torresensis. ¿Cylindrocarpon¿ macrodidymum fue la única especie aislada de las raíces de malas hierbas. En los análisis de suelos realizados mediante multiplex, nested PCR así como mediante qPCR se observó un elevado porcentaje de detección del complejo I. macrodidyma en muestras de ADN de suelo, mientras que el porcentaje de detección de I. liriodendri fue menor. Las mismas técnicas descritas para campos de plantas madre se utilizaron para estudiar los suelos de campos de vivero y de viñedos comerciales. Los resultados obtenidos en estos dos tipos de campos fueron similares a los obtenidos en campos de plantas madre. Finalmente, se estudió el efecto de la temperatura, pH y potencial osmótico (¿s) sobre el crecimiento miceliar, la esporulación y la producción de clamidosporas de ¿C.¿ liriodendri, ¿C.¿ macrodidymum y ¿C.¿ pauciseptatum, con el objetivo de mejorar el conocimiento de los factores que afectan al crecimiento, reproducción y supervivencia de estos patógenos. Todos los aislados estudiados crecieron en un rango de temperaturas comprendido entre 5 y 30ºC. Se observó crecimiento miceliar en un rango de pH comprendido entre 4 y 8. Respecto al efecto del ¿s, el crecimiento miceliar fue mejor en medio de cultivo PDA ajustado a -0,5, -1,0 y/o -2,0 MPa en comparación con el crecimiento miceliar observado en PDA sin ajustar a ningún ¿s (-0,3 MPA). La mayoría de los aislados de ¿Cylindrocarpon¿ esporularon a todas las temperaturas, pHs y valores de ¿s estudiados. En general, la producción de clamidosporas no se vio afectada por la temperatura, el pH y el ¿s.
Agustí Brisach, C. (2013). Studies on the epidemiology of black-foot disease of grapevine in Spain [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27598
TESIS

Noseomsis of the European honeybee, Apis mellifera L., is caused by two species of Microsporidia: Nosema ceranae and N. apis. Both species infect primarily the midgut of adult honeybees and have been reported as the third major cause of honeybee losses in Canada. Despite their importance few studies have examined their epidemiology. The current study monitored both species using duplex quantitative Real-Time PCR to determine the seasonal patterns, and potential transmission sources (glands and hive debris) in naturally infected hives from June 2008 to July 2010. Seasonal patterns of both Nosema species differed throughout the years with N. ceranae displacing N. apis. Results also demonstrated the presence of both species in glands suggesting that gland secretions may transmit the parasites. Hive debris and frass also contained spores suggesting that it may transmit the parasites and that bees need not be killed to determine if a hive is infected.
La nosémose des abeilles domestiques, Apis mellifera L., est causée par deux espèces microsporidiennes: Nosema ceranae et N. apis. Elles infectent principalement l'intestin moyen des abeilles et sont la troisième cause de perte d'abeilles au Canada. Malgré ceci, très peu est connu de leurs épidémiologies. Cet étude a examiné les deux espèces en utilisant un duplex de PCR quantitatif pour examiner les variations saisonnières des espèces et divers manières de transmission (glandes et débris de ruche) en des ruches naturellement infectées entre juin 2008 et juillet 2010. Les résultats ont démontré différentes variations saisonnières et que N. ceranae déplace N. apis. Les deux espèces étaient présentes dans les glandes ce qui suggère que leurs sécrétions peuvent transmettre les parasites. Elles étaient aussi présentes dans les débris et les fèces ce qui suggère que ces matières peuvent servir de vecteurs d'infections. De plus, ces résultats proposent une méthode non invasive afin de combattre Ia nosémose des abeilles domestiques car il n'est pas nécessaire de sacrifier des abeilles afin de détecter Ia présence de parasites.

O desenvolvimento industrial tem, como conseqüência, a maior geração de resíduos, muitos deles tóxicos aos seres vivos. Dentre esses, benzeno, tolueno e xilenos (BTX), derivados do petróleo, estão contaminando aqüíferos por acidentes no transporte e no armazenamento. Por esse motivo, diversas pesquisas têm sido realizadas buscando formas de biodegradar BTX. Esses trabalhos indicam que os principais fatores que podem influenciar a degradação biológica dos BTX são temperatura, pH, disponibilidade de nutrientes, concentração de tóxicos e diversidade de microrganismos. Visando contribuir com o estudo desses fatores, este trabalho teve por objetivo avaliar a influência do inóculo e de aceptores de elétrons no processo de degradação anaeróbia de BTX. Neste trabalho três inóculos foram pesquisados: 1- biomassa proveniente de reator anteriormente submetido à mistura de gasolina comercial e água; 2- biomassa proveniente de reator da estação de tratamento de esgoto da USP - São Carlos; 3- biomassa proveniente de reator tratando água residuária de abatedouro de aves. Os resultados obtidos comprovaram que a origem do inóculo foi fundamental na degradação anaeróbia de BTX, pois os inóculos apresentaram diferentes períodos de adaptação e porcentagens de degradação do tóxico. Depois de 93 dias de operação os inóculos 1, 2 e 3 apresentaram eficiência de remoção de BTX da ordem de 57%, 83% e 90%, respectivamente. O reator com o inóculo 3 foi submetido a condições metanogênica, sulfetogênica com presença e ausência de Ferro (III). Os resultados demonstraram que a degradação dos BTX foi influenciada pelas diferentes condições adotadas. A adição de Fe (III) melhorou a degradação dos BTX, do reator sob condições sulfetogênicas.
The industrial development has increased the generation of residues. Some of them are toxics and impact the environment. Benzene, toluene and xylenes (BTX), petroleum sub products, are examples of such toxic compounds. These compounds may contaminate aquifers as a result of accidents during transportation or of leakages of storage tanks. Several factors are reported to affect the biodegradation of BTX, such as: temperature, pH, availability of nutrients, concentration of toxics and diversity of microorganisms. This research aimed to study some of these factors, such as different inoculum sources and different electrons acceptors during BTX degradation processes in an horizontal-flow anaerobic immobilized biomass (HAIB) reactor. In this research three inocula were studied: 1- an adapted microbial community for BTX degradation; 2 - microorganisms collected from a pilot-scale UASB reactor treating domestic wastewater; and 3 - Microorganisms collected from an UASB treating poultry slaughterhouse industry wastewater. The results have shown that the inoculum sources were fundamental to the adaptation period for the toxic biodegradation, producing different BTX removal efficiencies. After 93 days of operation, the inocula 1, 2 and 3 showed BTX removal efficiency of 57, 83 and 90%, respectively. The inoculum 3 was submitted to conditions of methanogesis and sulfetogenesis in the presence and absence of Fe (III). The results demonstrated that BTX degradation was affected by the different conditions adopted, showing that the addition of Fe (III) improved biodegradation in the reactor under sulfate reduction condition.

La croissance de plants de douglas et d'épicéa est nettement améliorée en pépinière par inoculation contrôlée avec la souche L. Bicolor S238N. Pour évaluer l'efficacité de cette souche en terme de compétitivité et de persistance après transplantation en forêt, nous avons déterminé par morphotypage et ribotypage son taux d'infection sur douglas et épicéa en pépinière puis sur des plantations d’âge diffèrent. Le polymorphisme des régions ITS et IGS1 de l'ADNr a été étudié par PCR/RFLP. L'identification L. Bicolor S238N au sein de populations fongiques complexes a nécessité une caractérisation précise de son polymorphisme à partir des séquences variables de l'ADNr. Plus d'une soixantaine d'espèces de champignons ectomycorhiziens a été analysée par ribotypage de l'ITS. Si le polymorphisme de l'ITS permet le ribotypage interspécifique des espèces testées, seul le polymorphisme d'IGS1 grâce à la présence d'un hétéroduplex, permet une discrimination spécifique de la souche introduite L. Bicolor S238N. Dans tous les essais analyses, L. Bicolor S238N ne semble pas être capable de se disséminer au-delà des parcelles dans lesquelles il a été introduit. En pépinière, une ou deux années après inoculation, les taux de mycorhization des plants de douglas et des boutures d'épicéa par L. Bicolor S238N sont de 80 à 90% par ribotypage et morphotypage. Après transplantation des boutures d'épicéa sur deux sites forestiers ou la compétition avec les souches locales ectomycorhiziennes est plus forte qu'en pépinière, le pourcentage de mycorhizes formés par L. Bicolor S238N chute rapidement à 4%. Ces mycorhizes sont répartis sur tout le système racinaire. Après transplantation des boutures de douglas sur un site récemment abandonne par l'agriculture, le pourcentage de mycorhizes formés par L. Bicolor S238N représente encore 45% des mycorhizes deux ans après transplantation. Le ribotypage apporte donc un supplément d'informations et diffère fortement du morphotypage rendu difficile par les conditions environnementales et l’âge des plants. Cependant, le ribotypage ne peut être exclusif puisque certaines espèces n'ont pu être ribotypées à partir de leurs mycorhizes. Ce travail démontré que le ribotypage peut être appliqué à l'étude du comportement de populations de souches fongiques introduites ou naturelles à partir des mycorhizes formées par celles-ci.

Understanding the factors that shapes the microbial community assembly in activated sludge wastewater treatment processes provide a conceptual foundation for improving process performance. The aim of this study was to compare two major theories (deterministic theory and neutral theory) regarding the assembly of microorganisms in activated sludge: Six lab-scale activated sludge sequencing batch reactors were inoculated with activated sludge collected from three different sources (domestic, industrial, and sugar industry WWTP). Additionally, two reactors were seeded with equal proportion of sludge from the three WWTPs. Duplicate reactors were used for each sludge source (i.e. domestic, industrial, sugar and mix). Reactors were operated in parallel for 11 weeks under identical conditions. Bacterial diversity and community structure in the eight SBRs were assessed by 16S rRNA gene pyrosequencing. The 16S rRNA gene sequences were analyzed using taxonomic and clustering analysis and by measuring diversity indices (Shannon-weaver and Chao1 indices). Cluster analysis revealed that the microbial community structure was dynamic and that replicate reactors evolved differently. Also the microbial community structure in the SBRs seeded with a different sludge did not converge after 11 weeks of operation under identical conditions. These results suggest that history and distribution of taxa in the source inoculum were stronger regulating factors in shaping bacterial community structure than environmental factors. This supports the neutral theory which states that the assembly of the local microbial community from the metacommunity is random and is regulated by the size and diversity of the metacommunity. Furthermore, sludge performance, measured by COD and ammonia removal, confirmed that broad-scale functions (e.g. COD removal) are not influenced by dynamics in the microbial composition, while specific functions (e.g. nitrification) are more susceptible to these changes.

With increasing energy demand, decreasing oil supply, and continuously accumulating waste in landfills, the interest in converting lignocellulosic biomass to liquid fuels has grown. The MixAlco™ process requires no exogenous enzymes, no sterility, can be adapted to any biodegradable feedstock, and converts lignocellulosic biomass into valuable chemicals and transportation fuels. This work focuses on the effects different feedstocks and inocula have on mixed-acid/hydrogen fermentations. When volatile solids (VS) are digested, mixed-acid fermentations produce hydrogen gas as a secondary byproduct. Hydrogen is only produced when there is an excess of NADH within the cell and when the energy selectivity (gamma) of the system has not been met. Continuous fermentations of paper produced 16.7 g carboxylic acid/L and 15.7 mL H2/g VS digested. Continuous fermentations of pretreated bagasse produced 17.1 g carboxylic acid/L and 41.1 mL H2/g VS digested. Both fermentations produced a fraction of the theoretical amount of hydrogen. The paper fermentation had a hydrogen percent yield of 6.9 percent, whereas the bagasse fermentation had a hydrogen percent yield of 22.6 percent. Hydrogen production was capped at this level because gamma had been met for these systems. The Bioscreening Project, a joint project between three departments, sought to improve the MixAlco™ process by finding natural cultures containing high biomass converters and high acid producers. A total of 505 inoculum samples were collected from 19 sites and screened using paper and yeast extract fermentations. The best converters were analyzed with Continuum Particle Distribution Modeling (CPDM). Nine inocula were run in paper and yeast extract countercurrent fermentations in which the overall performance varied less than 13 percent. Comparisons between six countercurrent train cultures showed an average culture similarity of 0.40 (Yue-Clayton similarity). With the dissimilar microbial cultures and the very similar fermentation performance, the performance of the MixAlco™ process depends on fermentation conditions, not on the microorganisms. Batch fermentations of office paper wastes, pineapple residue, Aloe vera rinds, wood molasses, sugar molasses, extracted algae, non-extracted algae, crude glycerol, obtained from the biodiesel process, and pretreated water hyacinths produced sufficient carboxylic acids and had sufficiently high conversions to be viable substrates for the MixAlco™ process.

博士
國立中興大學
植物病理學系所
103
Abstract Sweet potato [Ipomoea batatas L. (Lam)], the dicotyledonous plant of the family Convolvulaceae, is the seventh most important food crop in the world after wheat, rice, maize, potato, barley and cassava. Besides food supply, sweet potato has diverse uses in green source, ornamental, feed, starch and liquor manufacture, human consumption, biofuel and bioplastic production, etc. Many cultivars have been currently developed for different uses through the world. Among these cultivars, vegetable sweet potato (VSP) has been bred for edible leafy vegetable and can produce a lot of leaves, tender shoots and small/non tubers constantly throughout the growth period in whole year period, especially, summer and rainy season. The VSP is considered as an important green source in summer or rainy season in Taiwan, and similar cultivars of VSP have been bred and grew in Japan. A new disease, Bacterial wilt (BW) caused by Ralstonia solanacearum (RS) broke out during 2000’s and reduced 30 to 80% yield of VSP last decade in Taiwan. The R. solanacearum isolates obtained from diseased VSP were identified as Ralstonia solanacearum phylotype I race 1 biovar 4 (R1bv4) based on physical and molecular analyses. Moreover, these isolates also caused wilting in convolvulaceous, solanaceaous and cruciferous plants. Field investigation indicated that R1bv4 was generally distributed in soil of VSP fields with 1.3×102 to 9.5×105 cfu/g soil. Further detection showed R1bv4 could latently infect healthy VSP cuttings with 2 to 98% isolation frequency. The severity of BW was closely related to R1bv4-carried VSP cuttings (R=0.913); however, the severity of BW did not show significant correlation with the R1bv4 density in soil (R=0.086). Similar phenomenon was observed in greenhouse test. Thus, the cuttings carried R1bv4 were more important inocula source than the R1bv4 residing in soil. The distribution of R1bv4 in VSP indicated that the terminal shoots or erect stems had low R1bv4 containation perecentage (<31%) and creeping stem had high R1bv4 containation percentage (45 to 100%) 8 wks after the VSP planted in infested soil (106 cfu/g soil). Results demonstrated that R1bv4 did not consistently move to the part of erect stem cuttings. For confirming the efficacy of the erect stem cutting on control BW of VSP in the fields, the erect stem cuttings were collected from VSP field. The results revealed that the erect stem cuttings used as new plants could decrease the BW in field. Moreover, companied with early R1bv4 detection in erect stems could increase the control efficient of BW in VSP production area. In this study, a bacterial endophyte, Bacillus amyloliquefaciens SPX1 from healthy VSP in Dali, had good ability to inhibit the growth of R1bv4 on TTC medium. The further experiment showed that the SPX1 isolate could decrease the wilting development of VSP in greenhouse and field conditions by soaking treatment. In addition, a resistance line of VSP, VSPSL-1, showed high reistance to bacterial wilt in field. Thus, the VSPSL-1 line is a promising cultivar resistant to R1bv4 in the future.