Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2015-11-11T14:40:30Z No. of bitstreams: 1 texto completo.pdf: 2597471 bytes, checksum: d356a04cdee8348ea7e9d4ca548e8b79 (MD5) / Made available in DSpace on 2015-11-11T14:40:30Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2597471 bytes, checksum: d356a04cdee8348ea7e9d4ca548e8b79 (MD5) Previous issue date: 2015-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A associação de Aphelenchoides besseyi a sementes de gramíneas forrageiras tem implicações quarentenárias que limitam a sua comercialização para muitos dos países importadores das sementes brasileiras. Como várias outras espécies de Aphelenchoides sem importância econômica são relatadas em associação a sementes de forrageiras, é imprescindível a identificação precisa de A. besseyi. Deste modo, realizaram-se as caracterizações morfológica, morfométrica e molecular de populações de A. besseyi associadas a sementes de forrageiras cultivadas no Brasil, comparando-as com populações de A. besseyi provenientes da Costa Rica, Espanha e Japão. Primers e sondas específicos foram desenhados, a partir da região LSU rDNA, e testados usando PCR em tempo real. A caracterização das regiões SSU, LSU e COI comprovaram a ocorrência de uma espécie geneticamente distante de A. besseyi associada às sementes de forrageiras no Brasil. De acordo com as análises filogenéticas das regiões SSU e COI, esta outra espécie, trata-se de A. fujianensis. Foi possível desenvolver e usar os ensaios diagnósticos para a detecção de A. besseyi e A. fujianensis. Com o uso dos primers/sonda específicos foi possível detectar o DNA alvo extraído a partir de um único nematoide. Ainda, foram identificadas duas sequências distintas na região LSU em uma população de A. besseyi, constituindo o primeiro relato da ocorrência de variabilidade intraindividual na região LSU do rDNA nesta espécie. Em adição, a alta identidade de uma destas sequências à A. fujianensis reforçou a proximidade filogenética destas espécies e a necessidade de uma extensiva investigação para se estimar a frequência deste fenômeno. / The association Aphelenchoides besseyi gramineous forage seed has quarantine implications that limit their marketing for many of the importing countries of these seeds. As many other Aphelenchoides species with no economic importance are reported in association with forage seeds, it is essential an accurate identification of A. besseyi. Thus, morphological, morphometric and molecular characterizations was undertaken using A. besseyi populations associated with gramineous forage seeds grown in Brazil, comparing to populations of A. besseyi from Costa Rica, Spain and Japan. Specific primers and probes were designed from LSU rRNA gene, and tested using real time PCR assays. The characterization of SSU, LSU, and COI proved the occurrence of a species genetically distinct from A. besseyi associated with gramineous forage seeds in Brazil. According to the phylogenetic analyzes of SSU and COI regions, this species is A. fujianensis. It was possible to develop diagnostic assays and use them to detect A. besseyi and A. fujianensis. The primers and probes were able to detect the DNA target extracted from a single nematode. Furthermore, two different sequences were identified in the LSU gene in one of A. besseyi populations studied, constituting the first report of intra-individual variation in LSU rDNA for this species. In addition, the high identity of one of these sequences with A. fujianensis reinforced the phylogenetic proximity of these species and the need for extensive research to estimate the frequency of this phenomenon.

An introduction to nematode systematics is provided which deals broadly with the history of the classification of nematodes, the controversial usage of the Phylum names Nemata Cobb, 1919 and Nematoda (Rudolphi, 1808) Lankester, 1877 and the reason why the name Nematoda was used in the present study. The classification, diagnosis and bionomics of the genus Aphelenchoides Fischer, 1894, the genus to which A. arachidis Bos, 1977 belongs is discussed. The section on bionomics is included to capture the astounding ability of this group of organisms to adapt to different trophic levels, a concept that is used to attempt an explanation for the ability of a supposedly African nematode, A. arachidis, to infest an alien crop species (groundnut). The ability of Aphelenchoides spp. to adapt to different host plant species is discussed, as well as the ability of the groundnut plant to mature its pods underground, a characteristic that predisposes these plants to a host of pathogens. The damage caused by two of the most important endoparasitic nematode species on groundnut, A. arachidis and Ditylenchus africanus Wendt, Swart, Vrain & Webster, 1995 were compared with each other. The South African population of A. arachidis was found predominantly in the shells of groundnut, whereas they were found in the shells, roots, hypocotyls and testas of the groundnut plants in Nigeria. The present study showed that A. arachidis and D. africanus occur together in groundnut in South Africa with D. africanus usually being the dominant species. In only one instance, at Bullhill (Vaalharts Irrigation Scheme, Northern Cape), the groundnut shells and testas were infested by A. arachidis alone. The importance of plant quarantine in South Africa is dealt with and the aims and principles of quarantine, as well as the different guidelines that have to be adhered to when deciding on the quarantine status of an organism are explained. Descriptions are provided of the methods used to prepare specimens for viewing with the light microscope (LM) and the scanning electron microscope (SEM), as well as the procedures of the molecular study. A morphological and morphometrical description of A. arachidis specimens from South Africa, as well as a comparison with specimens from Nigeria was done. Differences between the South African and Nigerian populations included, respectively, a lower b-value (7 - 11 vs 10 - 18), more lateral lines (2 - 4 vs 2), a slightly shorter stylet (8-10 m vs 10 - 12 m) and a longer length of the post-uterine sac as a percentage of the distance from vulva to anus (41 - 96 % vs ± 50 %). Scanning electron micrographs of this species are presented for the first time and shows the morphology of the lip region and lateral lines. Since both A. arachidis and A. blastophthorus were detected in the pods, a study was done to evaluate a PCR-based diagnostic method for the identification of these species and to compare the results with those reported in literature. Restriction fragment length polymorphisms (RFLPs) in the rDNA fragment were used to compare and differentiate between nematode species. The differences encountered within the South African population (morphological, morphometrical and molecular) warrant a study of more specimens from more localities. Through this it could be ascertained whether the South African population is a subspecies of A. arachidis or if this species just differs widely between localities. Future research should focus on a survey of the groundnut producing areas in South Africa to determine the distribution and economic impact of A. arachidis. The incidence of A. arachidis on other agricultural crops, especially those used in rotation with groundnut, also needs to be determined. The next issue to address is what enables a supposedly endemic species to Africa, A. arachidis, to parasitize an alien plant species (groundnut) from South America. Screening of the endemic bean family (Fabaceae) in Africa for the presence of A. arachidis, could hold the answer to this question. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

An introduction to nematode systematics is provided which deals broadly with the history of the classification of nematodes, the controversial usage of the Phylum names Nemata Cobb, 1919 and Nematoda (Rudolphi, 1808) Lankester, 1877 and the reason why the name Nematoda was used in the present study. The classification, diagnosis and bionomics of the genus Aphelenchoides Fischer, 1894, the genus to which A. arachidis Bos, 1977 belongs is discussed. The section on bionomics is included to capture the astounding ability of this group of organisms to adapt to different trophic levels, a concept that is used to attempt an explanation for the ability of a supposedly African nematode, A. arachidis, to infest an alien crop species (groundnut). The ability of Aphelenchoides spp. to adapt to different host plant species is discussed, as well as the ability of the groundnut plant to mature its pods underground, a characteristic that predisposes these plants to a host of pathogens. The damage caused by two of the most important endoparasitic nematode species on groundnut, A. arachidis and Ditylenchus africanus Wendt, Swart, Vrain & Webster, 1995 were compared with each other. The South African population of A. arachidis was found predominantly in the shells of groundnut, whereas they were found in the shells, roots, hypocotyls and testas of the groundnut plants in Nigeria. The present study showed that A. arachidis and D. africanus occur together in groundnut in South Africa with D. africanus usually being the dominant species. In only one instance, at Bullhill (Vaalharts Irrigation Scheme, Northern Cape), the groundnut shells and testas were infested by A. arachidis alone. The importance of plant quarantine in South Africa is dealt with and the aims and principles of quarantine, as well as the different guidelines that have to be adhered to when deciding on the quarantine status of an organism are explained. Descriptions are provided of the methods used to prepare specimens for viewing with the light microscope (LM) and the scanning electron microscope (SEM), as well as the procedures of the molecular study. A morphological and morphometrical description of A. arachidis specimens from South Africa, as well as a comparison with specimens from Nigeria was done. Differences between the South African and Nigerian populations included, respectively, a lower b-value (7 - 11 vs 10 - 18), more lateral lines (2 - 4 vs 2), a slightly shorter stylet (8-10 m vs 10 - 12 m) and a longer length of the post-uterine sac as a percentage of the distance from vulva to anus (41 - 96 % vs ± 50 %). Scanning electron micrographs of this species are presented for the first time and shows the morphology of the lip region and lateral lines. Since both A. arachidis and A. blastophthorus were detected in the pods, a study was done to evaluate a PCR-based diagnostic method for the identification of these species and to compare the results with those reported in literature. Restriction fragment length polymorphisms (RFLPs) in the rDNA fragment were used to compare and differentiate between nematode species. The differences encountered within the South African population (morphological, morphometrical and molecular) warrant a study of more specimens from more localities. Through this it could be ascertained whether the South African population is a subspecies of A. arachidis or if this species just differs widely between localities. Future research should focus on a survey of the groundnut producing areas in South Africa to determine the distribution and economic impact of A. arachidis. The incidence of A. arachidis on other agricultural crops, especially those used in rotation with groundnut, also needs to be determined. The next issue to address is what enables a supposedly endemic species to Africa, A. arachidis, to parasitize an alien plant species (groundnut) from South America. Screening of the endemic bean family (Fabaceae) in Africa for the presence of A. arachidis, could hold the answer to this question. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

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.