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.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 57-58).

Made available in DSpace on 2015-03-26T13:37:46Z (GMT). No. of bitstreams: 1 texto completo.pdf: 937955 bytes, checksum: e994bbbd173a1c574d82216b3fb1e780 (MD5) Previous issue date: 2008-04-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Exploratory assessments of phytopathogens associated with Miconia calvescens to be used for biological control have pointed the nematode Ditylenchus gallaeformans, a causal agent of galls and deformations in aerial tissues of Melastomataceae as being potentially fit for such purpose. The description of the new species with the proposition of the name D. gallaeformans is in submission phase for the publication. Considering the interaction of Melastomataceae with this nematode, the aim of this work was to study the biological and ecological aspects of the new species; galls histopathology induced in their hosts; host range; and the impact of the nematodes on plants of M. calvescens. D. gallaeformans host range was restricted to the plants of the family Melastomataceae with those of the genus Miconia being considered the most susceptible. D. gallaeformans was pathogenic to M. calvescens, both the Hawaii and Brazil biotypes. D. gallaeformans presented the typical habit of a migrant ectoparasite with life cycle mean duration of 19 days, from unicellular egg formation to the reproductive female phase. Rest stage at the fourth stage juvenile phase (J4), was verified, when the nematodes are in anhydrobiosis, what guarantees their survival in dehydrated plant material for up to 6 months. The nematode population in Viçosa, MG increased in the periods of higher temperatures; however, population density did not correlate with the climatic variables. The foliar galls formed by D. gallaeformans originated from hyperplasia of the fundamental meristem cells in the leaf primordia. The galls presented central cavities housing the nematodes and connected to the external environment. These cavities were surrounded by layers of dense cells responsible for supplying food to the nematodes. The most efficient inoculation method was the deposition of nematode suspension on the leaf primordia. A positive correlation was found among incidence, severity, and nematode population in plants inoculated at different concentrations of D. gallaeformans inoculum. The third leaf pair emitted after inoculation presented high correlation with incidence and severity, being considered the ideal point for evaluation of these variables. There was a decrease in the development of plants of M. calvescens with increased concentration of the inoculum of D. gallaeformans. It was concluded that D. gallaeformans is specific for the family Melastomataceae, with potential for the biological control of M. calvescens, in view of the damages caused to the plants. / Levantamentos exploratórios de fitopatógenos associados à Miconia calvescens para uso em controle biológico apontaram o nematóide Ditylenchus gallaeformans, agente causal de galhas e deformações em tecidos aéreos de melastomatáceas, como tendo potencial para este fim. Considerando a interação de melastomatáceas com este nematóide, objetivou-se estudar os aspectos biológicos e ecológicos da nova espécie; a histopatologia das galhas induzidas em seus hospedeiros; a gama de hospedeiros; e o impacto do nematóide em plantas de M. calvescens. A gama de hospedeiros de D. gallaeformans ficou restrita às plantas da família Melastomataceae e as do gênero Miconia foram consideradas as mais suscetíveis. D. gallaeformans foi patogênico à M. calvescens, tanto do biótipo do Havaí quanto do Brasil. D. gallaeformans apresentou o hábito típico de um ectoparasita migrador, com duração média do ciclo de vida desde ovo unicelular até a fase de fêmeas reprodutivas de 19 dias. Foi verificada a presença do estádio de repouso na fase de juvenil de quarto estádio (J4) quando os nematóides se encontram em anidrobiose, o que garantiu ao nematóide sobreviver em material vegetal desidratado por até seis meses. A população de nematóides em Viçosa, MG, foi maior nos períodos de temperaturas mais elevadas; entretanto, a densidade populacional não se correlacionou com as variáveis climáticas. As galhas foliares formadas por D. gallaeformans foram originadas da hiperplasia de células do meristema fundamental nos primórdios foliares. As galhas apresentaram cavidades centrais habitadas pelos nematóides e com ligação ao ambiente externo. Estas cavidades apresentaram, em seu entorno, camadas de células com conteúdo celular denso, responsável pelo fornecimento de alimento para os nematóides. O método de inoculação mais eficiente foi a deposição da suspensão de nematóides nos primórdios foliares. Houve correlação positiva entre incidência, severidade e população de nematóides em plantas inoculadas com diferentes concentrações de inóculo de D. gallaeformans. O terceiro par de folhas, emitido após a inoculação, apresentou alta correlação com a incidência e a severidade, sendo considerado o ponto ideal para avaliação destas variáveis. Houve redução no desenvolvimento de plantas de M. calvescens com o aumento da concentração de inóculo de D. gallaeformans. Concluiu-se que D. gallaeformans é especifico para a família Melastomataceae, com potencial para o controle biológico de M. calvescens, em vista dos danos causados às plantas.

Ditylenchus Dipsaci (Kuhn) Filipjev. is one of the most destructive nematodes to crop plants. It attacks and damages more than 300 species of cultivated and uncultivated plants. The nematode can be differentiated into many races, each of them having a preference for a group or even a single plant species. Alfalfa stem nematode is one of the races in this species which attacks the above ground portion of alfalfa but does not infest the roots. Larvae of this nematode may migrate from the plant tissue to soil in moist conditions. These nematodes migrate actively to nearby plants or are carried by agricultural tools or wind to reach plants at some distance away, causing a new infection.

Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2009.

ZUSAMMENFASSUNG Nematoden rufen weltweit erhebliche Verluste in der Kartoffelproduktion hervor. Der Knollenfäule-Nematode Ditylenchus destructor Thorne 1945 und das Stock-und Stangelälchen Ditylenchus dipsaci Kühn 1857 Filipjev, 1936, verursachen Läsionen an der Kartoffelknolle, was deren Qualität und Marktwert verringert. Diese Nematoden sind aufgrund ihres umfangreichen Wirtspflanzenspektrums schwierig zu kontrollieren und werden daher in vielen Ländern als Quarantäne-Nematoden geführt. In der hier vorliegenden Doktorarbeit wurden Experimente durchgeführt, um die Wechselwirkung von Kartoffel mit jeder dieser beiden Nematodenarten zu untersuchen. Verschiedene Populationen von D. destructor und D. dipsaci wurden molekular und morphometrisch charakterisiert. Die Gensequenz kodierend für die Untereinheit I der Cytochrom Oxidase (COI) auf der mitochondrialen DNA (mtDNA) wurde analysiert, um eine phylogenetische Beziehung zwischen den untersuchten Populationen darzustellen. Die Ergebnisse zeigten zwei deutlich getrennte Cluster für die D. destructor und die D. dipsaci Populationen. Eine Diskriminanzanalyse der morphometrischen Daten von Männchen und Weibchen von D. destructor und D. dipsaci Populationen verdeutlichte, dass diese beiden Arten mittels a-ratio und ihrem Durchmesser unterschieden werden können. Die sich ergänzende Kombination von molekularen und morphometrischen Untersuchungen ermöglichte die Identifikation der untersuchten Arten. Es wurden zwei Gewächshausexperimente mit 25 angebauten Kartoffelsorten durchgeführt, um diese auf Resistenz und Toleranz gegenüber Nematoden zu testen. Dazu wurde ein Standard-Screening Protokoll entwickelt. Resistenz und Toleranz wurden gemäß der derzeitigen Definition (Nematologie) bewertet. Die relative Anfälligkeit und äußere Verletzung der Kartoffelknolle stellten sich als beste Parameter für die Beurteilung der Resistenz respektive der Toleranz heraus. Alle 25 untersuchten Kartoffelsorten waren weder resistent noch tolerant gegenüber D. destructor oder D. dipsaci. Jedoch wurden Unterschiede in der Toleranz der Sorten festgestellt. Im Vorfeld zum Pflanzenexperiment wurden die Populationsdichten von D. destructor und D. dipsaci und deren Einfluss auf Ertragsverlust untersucht. Die initiale Populationsdichte hatte einen signifikanten Effekt auf den Schaden an der Kartoffelknolle und den Fortpflanzungsfaktor der Nematoden unter Gewächshausbedingungen. D. destructor verursachte Schäden bereits bei einer geringeren initialen Populationsdichte als D. dipsaci. Unter Klimakammerbedingungen wurde gezeigt, dass die Temperatur Einfluss auf die Schadensrate von D. destructor und D. dipsaci an Kartoffelknollen nimmt. Im Gegensatz zu einer Temperatur von 16°C waren 26°C sowohl optimal für die Vermehrung von D. destructor als auch für D. dipsaci. Obwohl für D. destructor und D. dipsaci unterschiedliche Temperaturanforderungen beschrieben wurden, verursachten beide Arten in ähnlichen Temperaturbereichen äußere Verletzungen an der Kartoffelknolle. Beauveria bassiana ist ein weltweit verbreiteter Pilz, der vor allem zur Bekämpfung von Insektenschädlingen in der Kartoffelproduktion Anwendung findet. Doppelbefall von Kartoffeln mit B. bassiana Sporensuspensionen im Boden mit D. destructor oder D. dipsaci begünstigte die Nematoden, was zu einer erhöhten Nematodenfortpflanzung und Knollenbeschädigung führte. B. bassiana allein war nicht schädlich für die Kartoffel. Es wurde vermutet, dass B. bassiana eine indirekte Rolle in der Wechselwirkung Nematode-Kartoffel spielt. Vorschläge für zukünftige Experimente werden angebracht, die einen weiteren Beitrag zu den hier vorgestellten Studien leisten können.

HOST PLANT RESISTANCE AS A MANAGEMENT TOOL FOR DITYLENHUS AFRICANUS (MEMATODA: TYLENCHIDAE) ON GROUNDNUT {ARACHIS HYPOGAEA) Groundnut is an important cash crop both for commercial and smallscale farmers in South Africa. The effect of Ditylenchus africanus on groundnut is mainly qualitative, leading to downgrading of groundnut consignments. This nematode is difficult to control because of its high reproduction and damage potential. The objective of the study was to investigate the potential of host-plant resistance as an effective and economically-feasible alternative management tool for the control of D. africanus on groundnut. Selected groundnut genotypes were evaluated against D. africanus in microplot and field trials. PC254K1 and CG7 were identified as resistant to D. africanus. The resistance expressed by these two genotypes is sustainable under field conditions. The resistance expressed by PC254K1 is effective even at high population densities. This genotype consistently produced yields with a low UBS % at all nematode population levels. PC254K1 could therefore be used as a major source of resistance to D. africanus in the development of commercial cultivars. Although the breeding line PC287K5 also maintained low nematode numbers in some trials, its level of resistance does not seem to be as strong or as sustainable as that of PC254K1 or CG7. However, PC287K5 could still play an important role in the groundnut industry where lower D. africanus populations occur. The resistance expressed by PC254K1 is not transferred to leaf callus tissue of this genotype, confirming there is no short-cut for screening for resistance to D. africanus. The reproduction and damage potential of D. africanus populations from different geographically-isolated localities in the groundnut-production areas of South Africa was tested under controlled and semi-controlled conditions and were found to be similar to each other. Resistance of PC254K1 to all of the tested populations was confirmed. These results indicate that the presence of this resistant trait in a cultivar developed from PC254K1 should be sustainable over the whole groundnut-production area of South Africa. The absence of D. africanus from pod tissue of PC254K1 confirmed the genotype's resistance. The mechanism of resistance involved may be the inhibition of proper development of this nematode, preventing it to build up to damaging population levels. However, PC254K1 is not immune to this nematode since it does occur in small numbers on this genotype. The resistance trait in PC254K1 is seemingly governed by a number of genes, implying that it will be more durable under sustained pressure by D. africanus populations. Although markers associated with the resistance trait were mapped, they were not closely linked. Three putative qualitative trait loci (QTL's) were identified but markers associated with the resistance trait need to be refined and developed to be breeder-friendly in terms of marker-assisted selection. There are strong indications that CG7, which is a parent of PC254K1, may have more superior levels of resistance to D. africanus than PC254K1. The identification of markers closely associated with the resistance trait might, therefore, be more successful using CG7 in stead of PC254K1 / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2009.

HOST PLANT RESISTANCE AS A MANAGEMENT TOOL FOR DITYLENHUS AFRICANUS (MEMATODA: TYLENCHIDAE) ON GROUNDNUT {ARACHIS HYPOGAEA) Groundnut is an important cash crop both for commercial and smallscale farmers in South Africa. The effect of Ditylenchus africanus on groundnut is mainly qualitative, leading to downgrading of groundnut consignments. This nematode is difficult to control because of its high reproduction and damage potential. The objective of the study was to investigate the potential of host-plant resistance as an effective and economically-feasible alternative management tool for the control of D. africanus on groundnut. Selected groundnut genotypes were evaluated against D. africanus in microplot and field trials. PC254K1 and CG7 were identified as resistant to D. africanus. The resistance expressed by these two genotypes is sustainable under field conditions. The resistance expressed by PC254K1 is effective even at high population densities. This genotype consistently produced yields with a low UBS % at all nematode population levels. PC254K1 could therefore be used as a major source of resistance to D. africanus in the development of commercial cultivars. Although the breeding line PC287K5 also maintained low nematode numbers in some trials, its level of resistance does not seem to be as strong or as sustainable as that of PC254K1 or CG7. However, PC287K5 could still play an important role in the groundnut industry where lower D. africanus populations occur. The resistance expressed by PC254K1 is not transferred to leaf callus tissue of this genotype, confirming there is no short-cut for screening for resistance to D. africanus. The reproduction and damage potential of D. africanus populations from different geographically-isolated localities in the groundnut-production areas of South Africa was tested under controlled and semi-controlled conditions and were found to be similar to each other. Resistance of PC254K1 to all of the tested populations was confirmed. These results indicate that the presence of this resistant trait in a cultivar developed from PC254K1 should be sustainable over the whole groundnut-production area of South Africa. The absence of D. africanus from pod tissue of PC254K1 confirmed the genotype's resistance. The mechanism of resistance involved may be the inhibition of proper development of this nematode, preventing it to build up to damaging population levels. However, PC254K1 is not immune to this nematode since it does occur in small numbers on this genotype. The resistance trait in PC254K1 is seemingly governed by a number of genes, implying that it will be more durable under sustained pressure by D. africanus populations. Although markers associated with the resistance trait were mapped, they were not closely linked. Three putative qualitative trait loci (QTL's) were identified but markers associated with the resistance trait need to be refined and developed to be breeder-friendly in terms of marker-assisted selection. There are strong indications that CG7, which is a parent of PC254K1, may have more superior levels of resistance to D. africanus than PC254K1. The identification of markers closely associated with the resistance trait might, therefore, be more successful using CG7 in stead of PC254K1 / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2009.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-02-14T15:45:43Z No. of bitstreams: 1 texto completo.pdf: 3013347 bytes, checksum: 1284ed81fc4f3a5fe7379016ad1f819c (MD5) / Made available in DSpace on 2017-02-14T15:45:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3013347 bytes, checksum: 1284ed81fc4f3a5fe7379016ad1f819c (MD5) Previous issue date: 2015-12-11 / Ministério da Agricultura, Pecuária e Abastecimento. / Os objetivos deste trabalho foram determinar, entre os artigos regulamentados já com autorização fitossanitária de importação para o Brasil ainda não submetidos à análise de risco de pragas (ARP), as possíveis vias de ingresso do nematoide parasita de vegetais Ditylenchus destructor Thorne, 1945, praga quarentenária ausente no Brasil; avaliar o risco fitossanitário da introdução de D. destructor a plantas cultivadas na agricultura, horticultura e silvicultura, plantas não cultivadas, flora selvagem, habitats e ecossistemas no Brasil por esses produtos importados, a partir de avaliações semiquantitativas das suas probabilidades de entrada e estabelecimento em território nacional e dos seus potenciais de disseminação e de causar danos econômicos no Brasil; e propor medidas fitossanitárias a serem estabelecidas em normas oficiais do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) para mitigar para um nível aceitável o risco fitossanitário associado à introdução e disseminação de D. destructor pelas vias de ingresso no Brasil para as quais o risco fitossanitário fosse julgado inaceitável. A ARP foi conduzida por meio do esquema de apoio à decisão para ARP da Norma de Medidas Fitossanitárias n.o 5/3 (5), da Organização Europeia para Proteção de Plantas (EPPO), executada no software CAPRA (“Computer Assisted Pest Risk Analysis”). Os produtos vegetais de importação autorizada (PVIA) que são possíveis vias de ingresso para D. destructor foram determinados, filtrando-se os registros da base de dados de PVIA do MAPA a partir dos registros de espécies vegetais hospedeiras do nematoide, de países que têm registros de sua ocorrência e das partes vegetais para as quais há registros de que o nematoide possa se abrigar em alguma fase do seu ciclo de vida. As probabilidades semiquantitativas de entrada e de estabelecimento e os potenciais semiquantitativos de disseminação, de impacto econômico e de risco final da praga em cada via de ingresso, bem como os valores de suas incertezas, foram compostos a partir das respostas dadas às questões individuais do esquema da EPPO no CAPRA, utilizando a modelagem de decisão com atributos múltiplos por regras expressas em matrizes, contida no próprio software CAPRA e executada dentro do software livre de ambiente de modelagem “GeNIe”. O risco fitossanitário final de Ditylenchus destructor nas diversas vias de ingresso avaliadas foi considerado baixo, com incerteza média. Foi, portanto, considerado aceitável, não tendo sido necessária a adoção de medidas fitossanitárias adicionais para mitigar esse risco, além das medidas fitossanitárias gerais atualmente em vigor. / The objectives of this study were to determine, among the regulated articles already with phytosanitary import authorization to Brazil not yet submitted to pest risk analysis (PRA), the possible pathways to the plant parasitic nematode Ditylenchus destructor Thorne, 1945, absent quarantine pest in Brazil; to assess the phytosanitary risk of introducing D. destructor to cultivated plants in agriculture, horticulture and forestry, uncultivated plants, wild flora, habitats and ecosystems in Brasil by these imported products, from semiquantitative assessements of their likelihoods of entry and establishment in the country, and its potential to spread and cause economic damage in Brazil; and to propose phytosanitary measures to be established in official regulations of the Ministry of Agriculture, Livestock and Food Supply (MAPA) to mitigate to an acceptable level the phytosanitary risk associated with the introduction and spread of D. destructor by the pathways into Brazil for which the phytosanitary risk was deemed unacceptable. The PRA was conducted through the decision support scheme to PRA of the Phytosanitary Measures Standard No. 5/3 (5), of the European Plant Protection Organization (EPPO), performed in the CAPRA software ("Computer Assisted Pest Risk Analysis"). The plant products with authorized import (PVIA) that are possible pathways to D. destructor were determined by filtering the MAPA’s PVIA database records with the records of the nematode’s host plant species, countries that have records of its occurrence, and plant parts to which there are records that the nematode can take shelter at some stage of its life cycle. Semiquantitative likelihoods of entry and establishment, and semiquantitative potentials of spread, economic impact and final risk of the pest on each pathway, as well as the values of their uncertainties, were composed from the answers to individual questions of EPPO scheme in CAPRA, using the decision modeling with multiple attributes by rules expressed in matrices contained in the CAPRA software itself and executed in the free software of modeling environment "GENIE". The final phytosanitary risk of Ditylenchus destructor in the different assessed pathways was considered low, with medium uncertainty. It was therefore considered acceptable, and it was not necessary to adopt additional phytosanitary measures to mitigate this risk, beyond to the general phytosanitary measures currently in effect.

Made available in DSpace on 2014-06-11T19:32:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-12Bitstream added on 2014-06-13T18:42:55Z : No. of bitstreams: 1 favoreto_l_dr_jabo.pdf: 3329621 bytes, checksum: 36f575037615585fab467fb72c68c365 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Foi objetivo desta pesquisa: 1) Quantificar a população de nematóides e fungos em amostras de sementes procedentes dos principais Estados produtores do Brasil; 2) Estudar a taxonomia dos nematóides; 3) Estudar o processo de infecção de sementes de Brachiaria brizantha por nematóides; 4) Avaliar a eficácia da irradiação com 60Co e do tratamento químico para o controle dos nematóides. Amostras de 237 lotes de sementes de diferentes gramíneas forrageiras foram examinadas nos Laboratórios de Nematologia e de Fitossanidade da UNESP/FCAV, Câmpus de Jaboticabal, quanto à ocorrência de fungos e nematóides. No tratamento químico, usouse um lote de sementes infectadas por 1.350 Aphelenchoides sp. por 10 g. As sementes foram tratadas com doses de diferentes produtos, e como testemunha usaram-se sementes não-tratadas do mesmo lote. O experimento foi conduzido a campo em duas regiões distintas. Para irradiação, empregaram-se doses de 60Co, no Centro de Energia Nuclear na Agricultura (CENA), Piracicaba – SP, sendo que 160 g de sementes de B. brizantha foram irradiadas com a taxa de dose de 186,8 Gy/h. Em outro experimento, 10 g de sementes de B. brizantha, isentas de nematóide, foram colocadas em gerbox, sobre areia autoclavada. Em seguida, foram inoculados 10 mL de uma suspensão contendo 3.000 indivíduos de Aphelenchoides sexlineatus (partenogenética). Os tratamentos tanto químico quanto com 60Co demonstraram não ter efeito sobre a população do nematóide. Confirmou-se, neste estudo, que os nematóides infectam as sementes após elas caírem no solo. Nematóides e fungos são encontrados infectando sementes de diferentes espécies forrageiras. / It was the objective of this study: 1) To quantify the population of nematodes and fungi in samples of seeds from the main producer states of Brazil, 2) study the taxonomy of nematodes, 3) To study the process of infection of seeds of tropical grasses by nematodes, 4) Evaluate the effectiveness of irradiation with 60Co and chemical treatment to control nematodes. Samples of 237 seed lots of different grasses were examined in the Nematologia and Fitopatologia laboratory of UNESP / FCAV, from Jaboticabal Câmpus as the occurrence of fungi and nematodes. In the chemical treatment, used to a lot of seeds infected by 1350 Aphelenchoides sp. for 10 g. The seeds were treated with doses of different products and used it as a witness if untreated seeds from the same batch. The experiment was conducted under field conditions in two separate regions. For irradiation, using doses of 60Co, in the Centro de Energia Nuclear na Agricultura (CENA) Piracicaba - SP, of which 160 g of seeds of B. brizantha were irradiated with a dose rate of 186.8 Gy / h. In another experiment, 10 g of seeds of B. brizantha, free of nematode, were placed in gerbox on autoclaved sand. It was then inoculated 10 mL of a suspension containing 3000 specimens of Aphelenchoides sexlineatus. The both treatments, chemist and with 60Co showed no effect on the nematode population. It was confirmed in this study that the nematodes infect the seeds after they fall on the ground. Nematodes and fungi are found infected seeds of different forage species.