Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Mar. 2, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 158-175).

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

One of the most diverse groups of parasitic nematodes includes the nematodes of the suborder Trichostrongylina. Trichostrongyle systematic classification is based on the study of the anterior end, the female reproductive system, the male copulatory bursa and cuticular ridges, which make up the synlophe. These morphological characters also assist taxonomists to characterize species and assign them into one of the three superfamilies. Heligmosomoidea is the most diverse superfamily, including Viannaiidae. This family represents one of the major evolutionary radiations of trichostrongyles in South America. Members of Viannaiidae parasitize a variety of mammals endemic to the Neotropics including, but not limited to, the opossums. Viannaiids have great morphological variation in the reproductive organs of the females and the secondary sexual structures of the males (e.g., rays in the bursa). Consequently, the placement of these species in classification schemes has drastically changed over time. The prevailing taxonomy relies on the host used by the parasites as well as their geographic distribution. Viannaiidae has always included monodelphic nematodes with simple synlophes, yet it eventually included species in the genus Travassostrongylus, which the morphology is very distinct from the rest of the members of the family. Differences pertain to a greater number of ridges of the synlophe and the didelphic female reproductive system. These features are more similar to trichostrongyles in Herpetostrongylidae and Nicollinidae, which infect Australian vertebrates, the majority of which are marsupials. I herein document the diversity of this group by reporting the presence of a putative new species and use five gene regions to reconstruct the phylogeny of Viannaiidae exclusive of didelphid marsupials. I used the resulting phylogeny to test the monophyly of Travassostrongylus and Viannaia and to reconstruct the character evolution of the monodelphic/didelphic condition and the ornamentation of the cuticle. The phylogeny indicates that Viannaiidae is not monophyletic, recovering a clade with the Travassostrongylus species and trichostrongyles from Australian fauna. The tests for character reconstruction assist in determining that the didelphic condition and the presence of dorsal synlophe ridges in Travassostrongylus and Austrostrongylus may be traits inherited from a common ancestor. Furthermore, it was apparent that a character change from didelphic to monodelphic occurred in the common ancestor of the Viannaia species. This ancestor also underwent a change from a dorsal cuticle with ridges to a smooth cuticle. Though the study suggests that Viannaiidae is not monophyletic, the inclusion of more species from these genera and the viannaiids found in hystricognaths from the New World rodents will conclusively determine the affinities of the members of the family. Finally, I suggest that the relationship between the species in Travassostrongylus and the Australian parasites dates to the Gondwana landmass and that these trichostrongyles, or their ancestors, were present in the marsupials of that time period. The examination of microbiotheriids could provide more information and illuminate the factors that led to the evolutionary relationship between the parasites of America and Australia.

Traditional vineyard floor management in the eastern USA consists of mown resident vegetation in the aisle and herbicide bare driplines, promoting soil erosion and crusting, compaction, lowered water penetration, herbicide resistance, difficult weed management, increased plant parasitic nematode populations and decreased soil biodiversity for pest management. To investigate these issues, four novel vineyard floor management techniques and two N-fertilizer applications were investigated using nematode assemblages as a bioindicator of soil health. Main-plot groundcover treatments include: 1.) grower control, consisting of mown fescue (Festuca arundinacea) in the aisle with herbicide bare vine dripline, 2.) red fescue, creeping red fescue (Festuca rubra L.) established in both the aisle and vine dripline, 3.) successional, annually planted cereal rye (Secale cereale L.), spring oats (Avena sativa L.), and sorghum-sudan grass (Sorgum x drummondii) by planting them in succession with a no-till drill throughout the year, 4.) compost treatment consisted of a 2 to 1 mix of hardwood mulch and composted winery pomace applied across both the vineyard aisle and vine dripline. Split-plot nitrogen treatments include: 1.) no nitrogen fertility applied to grapevines, 2). 20 lb. N/ac applied to grapevine dripline at budbreak, bloom and veraison. The randomized complete block design with four main-plot treatments, two split-plot treatments and five blocks was established in 2013 and 2014 in a commercial mature Norton vineyard, planted in 2003, at 2.44 x 3.66 m spacing, in southern Illinois on a Hosmer silt-loam. The canonical analysis of principle components clearly revealed that compost and successional treatments were particularly effective at shifting nematode assemblages to higher populations of cp-5 nematodes to correlate with increases in soil respiration and organic matter, thus indicating establishment of a stable soil health structure both physically and ecologically. The results of the soil health analysis panel (soil respiration, water extracted organic carbon and water extracted macro-and micro-soil elements), consistently supported the interpretation of nematode community structure analysis. In fall 2015 the compost, red fescue and successional groundcovers combined with P and K soil fertility amendments increased water extractable K (WEK) in the aisle by 85%, 59% and 71%, respectively, compared to control; they similarly increased WEK in the aisle by 46%, 59% and 71%, respectively, in summer 2016. In the dripline WEK was increased 140%, 238% and 249%, respectively, by compost, red fescue and successional treatments that received no-N-prescription, compared to the control. The application of prescription-N increased WEK by 25% and 21%, respectively, in the compost and successional treatments that had a generous mulch layer. Soil P response to groundcover treatment clearly distinguished among each treatment the impact of nutrient turnover levels with water extracted P levels: successional > red fescue > compost > control, unique to each treatment. The water extracted mineral element levels detected with the soil health analysis were one-half to one-ninth the concentration extracted with the Mehlich-III test. Red fescue tripled the population of Pratylenchus spp. (236/100cc soil) in the dripline with prescription-N fertilization compared to no-N. Red fescue and successional treatments increased Helicotylenchus spp. populations by ~657% and ~172%, respectively, compared to compost (92/100cc soil) which closely resembled control response average in the dripline across 2015 and 2016. Prescription-N reduced Longidorus spp. by 78% compared to no-N treatment (23/100cc soil) in the dripline of fall 2015. Additionally, prescription-N added to the red fescue and successional treatments reduced Xiphinema spp. populations by 57% and 92%, respectively, compared to the control (52/100cc soil). Compost and successional groundcover treatments dramatically increased grapevine yield and crop size by 38% and 30%; and 29% and 38%, respectively, compared to grower control. The prescription N-fertilizer increased yield and crop size by 13% and 17%, respectively, compared to no-N. Compost and successional also increased Ravaz index by 33% and 60%, respectively, over control without reducing vine size which indicated their future vineyard sustainability.

Submitted by Rosana Amâncio (rosana.amancio@ufcg.edu.br) on 2018-07-12T21:53:47Z No. of bitstreams: 1 AMANDA GONÇALVES SANTOS - DISSERTAÇÃO PPGCNBio 2016..pdf: 3551999 bytes, checksum: db596e2a882aff72633f305307857dee (MD5) / Made available in DSpace on 2018-07-12T21:53:47Z (GMT). No. of bitstreams: 1 AMANDA GONÇALVES SANTOS - DISSERTAÇÃO PPGCNBio 2016..pdf: 3551999 bytes, checksum: db596e2a882aff72633f305307857dee (MD5) Previous issue date: 2016-07-14 / CNPq / Os nematódeos são os metazoários mais abundantes do planeta. Estima-se que três quartos, ou mais, de todos os animais da terra são nematódeos. Podem ser encontrados em todos os habitats que forneçam fontes de carbono orgânico disponíveis. Variam de acordo com a sensibilidade a poluentes e perturbação ambiental. Por esses motivos vem sendo utilizados, como ferramenta para biomonitoramento de ecossistemas. A resolução taxonômica diminui o problema do “impedimento taxonômico”, causado pela carência de pesquisadores nesta área e pela dificuldade na identificação dos organismos nos níveis taxonômicos mais baixos. Assim, objetivou-se comparar as estruturas populacionais nematofaunística, pelo uso de resoluções taxonômicas em três ambientes costeiros, a fim de ampliar a utilização da “resolução taxonômica” e enfatizar a sua importância como uma boa ferramenta de suporte as pesquisas de cunho taxonômico, principalmente nas que envolvam o monitoramento ambiental. Foram realizadas coletas em período chuvoso e seco, em ponto fixo da praia, do recife e do estuário de Pirangi do Sul - RN, Brasil. Os nematódeos encontrados foram identificados até o nível de espécie. Foram encontrados 46 gêneros e 56 espécies, pertencentes à 15 famílias, sendo 9 espécies novas para a ciência. As análises estatísticas mostraram que os níveis taxonômicos utilizados apontam diferenças na organização da comunidade, entre as estações de coleta, com exceção do nível específico. As diferenças também foram observadas para análises espaciais, com exceção do nível de ordem. A classificação até o nível de gênero se mostra taxonômicamente suficiente para interpretar os dados da comunidade nematofaunística da região de Pirangi do Sul-RN, para análises espaciais. / Nematodes are the most abundant metazoans in the planet. It is estimated that three-quarters or more of all land animals are nematodes. They can be found in all habitats that provide sources of organic carbon available. They still vary according to the sensitivity to pollutants and environmental disturbance. For these reasons it is being used as an instrument for biomonitoring ecosystems. The taxonomic resolution reduces the problem of "taxonomic impediment" caused by the scarcity of researchers in this area and the difficulty in identifying organisms at lower taxonomic levels. Thus, this study aimed at comparing the nematofaunistic population structures through the use of taxonomic resolutions in three coastal environments in order to expand the use of taxonomic resolution and emphasize its importance as a good resource support in the researches of taxonomic aspects, especially in those involving environmental monitoring. Samplings in rainy and dry season were made, in a fixed point at the beach, of the reef and estuary of Pirangi do Sul - RN, Brazil. The found nematodes were identified up to the species level. They were found 46 genera belonging to 15 families and 56 species being 9 of them new to science. Statistical analyzes showed that the taxonomic levels used in this research point to differences in the community´s organization, among the sampling stations, except the specific level. Differences were also observed for spatial analysis, with the exception of the order level. Classification up to the genus level has shown taxonomically enough to interpret the data nematofaunistic community of Pirangi-RN southern region for spatial analysis.

D.Phil. (Nematology) / Please refer to full text to view abstract

Teladorsagia circumcincta is a parasitic nematode which is a major cause of ovine parasitic gastroenteritis in temperate climatic regions. The parasite has developed resistance to the major anthelmintic drug classes and this challenges its future control. Vaccination is a potential alternative control method since sheep are able to develop protective immunity against this parasite. Although potential vaccine candidates have been revealed, the increasing gene datasets suggest that vaccinetarget selection may be aided by screening methods such as RNAi. This is a reverse genetic mechanism that causes highly specific gene silencing which was initially described and applied to defining gene function in Caenorhabditis elegans. Nevertheless, its application was more difficult than anticipated in parasitic nematodes because of the inconsistency of the silencing effect. In the unsuccessful cases, did the dsRNA penetrate the parasite and activate the RNAi pathway? Thus far, there are no internal controls that indicate the activation of the pathway. Are the RNAi pathway genes constantly transcribed or are they ‘switched on’ in response to the dsRNA exposure? The initial aim of the study was to determine potential marker genes in the RNAi pathway that could indicate the activation of the pathway in C. elegans. After the exposure to dsRNA from two target genes, the transcript levels of three candidate marker genes (Ce-dcr-1, Ce-ego-1 and Ce-rsd-3) were examined and showed that exposure to dsRNA has no effect on the transcript levels of these genes making them inappropriate markers for the activation of the RNAi pathway. The two target-genes were Ce-cpr-4 and Ce-sod-4 which had been proven to be consistently susceptible and refractory to RNAi, respectively. Another aim of the project was to develop an RNAi platform in T. circumcincta for use as a screening method for potential vaccine candidates. The targets selected for the in vitro RNAi included: five members of the Activation-associated Secreted Proteins (ASPs); a Macrophage migration Inhibitory Factor-like (Tci-mif-1) and a Surface Associated Antigen gene (Tci-saa-1), all of which have been associated with vaccine-induced protective immunity. The selection of the ASPs was based on a bioinformatic and transcriptomic analysis of the ASPs in T. circumcincta. The results showed successful knock-down only for three out of five ASP targets after 1 hour of soaking in gene-specific double stranded RNA (dsRNA) which illustrates the inconsistency and the target specificity of RNAi in T. circumcincta which has been observed in the past with other parasitic nematodes. Inconsistencies were also observed within the successful ASP targets with the results not being reproducible after several successful experiments. Potential reasons for the inconsistencies were examined with the duration of larval storage being a critical factor. Larvae stored for a short or long period of time were susceptible and refractory to RNAi, respectively. Experiments were also conducted to investigate how the ASPs relate to extracellular microvesicles (EMVs). These vesicles are considered to play an important role in the intercellular communication between parasites and their hosts, and thus represent potentially useful vaccine and/or drug targets. Transmission electron microscopy (TEM) confirmed that EMVs are excreted / secreted by the parasite and the proteomic analysis revealed several types of proteins within the vesicles such as: ASPs, Actins, Metallopeptidases, and RAB proteins. A comparative analysis of EMVs, EMV-free ES (Excretory / Secretory) and total ES products showed that approximately 35% of the proteins found in the vesicles could also be identified in EMV-free ES and in total ES products, whilst the remaining 65% were present only in EMVs.

M.Sc. (Nematology) / Please refer to full text to view abstract

Thesis (M. Agric. (Plant Production)) -- University of Limpopo, 2019 / Phytonematicides have allelochemicals as active ingredients and could be highly phytotoxic on crops being protected against nematode damage. In order to avoid phytotoxicity, the application concentration, technically referred to as mean concentration stimulation point (MCSP), along with the application interval, have to be empirically established. The Curve-fitting Allelochemical Response Data (CARD) computer-based model was adopted at the Green Biotechnologies Research Centre of Excellence (GBRCE) for developing the MCSP. The MCSP is computed from the CARD-generated biological indices and was technically defined as a phytonematicide concentration that could manage the nematode population densities without causing phytotoxicity to the test crop and it is plant-specific. The MCSP and application interval had been empirically established for different crops, but they had not been established for sweet potatoes. Therefore, the objective of the study was to determine the MCSP for Nemarioc-AL phytonematicide on Meloidogyne javanica-infected sweet potato cv. ꞌBopheloꞌ and its application interval. Sweet potato cuttings were planted in 25-cm diameter plastic bags containing steam-pasteurised loam soil and Hygromix at 3:1 (v/v) ratio. Each plant was inoculated with 5 000 eggs and second-stage juveniles (J2) of M. javanica, with seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL phytonematicide, arranged in a randomised complete block design, with five replicates. At 56 days after the initiation of treatment, the MCSP values for plant variables and plant physiology variables were 1.92 and 3.08% Nemarioc-AL phytonematicide, respectively. The overall sensitivity values for plant variables and plant physiology variables were 0 and 1 unit, respectively, showing that the sweet potato cv. ꞌBopheloꞌ was highly sensitive to the product. Nematode variables with increasing concentrations of Nemarioc-AL phytonematicide exhibited positive and quadratic relations. The life cycle of M. javanica and the derived MCSP were used to empirically establish the application interval. Briefly, the location and most materials and methods were as outlined above except that ‘weeks-per-month-of-30 days’, with the MCSP being applied on 0, 7.5, 15, 22.5 and 30 days (0, 1, 2, 3 and 4 weeks) serving as treatments, replicated eight times. At 56 days after the treatments, plant variables and increasing application interval exhibited positive quadratic relations with the average of 2.55 ‘week of-30-day-month’ translating to 19 days (2.55/4 × 30), with nematode variables exhibiting negative quadratic relationships. In conclusion, when the MCSP of Nemarioc AL phytonematicide on sweet potato cv. 'Bophelo' at 1.92% was applied every 19 days, it would not be phytotoxic, but it would be able to suppress nematode population densities of M. javanica. The MCSP for essential nutrient elements could be reduced to that of plant growth variables, since the products are not intended for use as fertilisers.