In its introduced southern hemisphere range, Sirex noctilio causes considerable mortality in non-native pine forests. In its native Eurasian range however, S. noctilio is of little concern perhaps due to interactions with a well-developed community of pine-inhabiting insects and their associated microorganisms. If such interactions occur, they may limit the woodwasp’s impact in its newly introduced range in North America. My research addresses two broad questions: 1) Does S. noctilio share its habitat with other insects and if so, with whom? 2) Is there evidence that co-habitants affect S. noctilio, and if so how might such interactions occur? Field studies undertaken to describe the woodwasp’s host-attack ecology in Pinus sylvestris showed S. noctilio activity occurred between mid-July and late August, and other phloem- and woodborers sometimes entered the tree after the woodwasp. Tree mortality occurred from two weeks to several months after initial woodwasp symptoms. Suppressed or intermediate trees, those with ≤ 25% residual foliage, or those with stem injury or previous woodwasp symptoms were most likely to have symptoms of woodwasp attack. A second field study conducted to identify associated insect species in S. noctilio-infested Pinus sp. showed the wasp was sometimes found alone, but usually shared the tree with other phloem- or woodboring insects, most commonly the curculionids Tomicus piniperda, Pissodes nemorensis and Ips grandicollis and the cerambycid Monochamus carolinensis. I found no indication that wasps were absent when beetles were present, but there was evidence that woodwasps were less abundant, but larger, when beetles were present. Experiments showed that indirect interactions can occur between the two insect groups via fungal associates of one or both. In the laboratory, the woodwasp symbiont was outcompeted by two beetle-associated fungi, Leptographium wingfieldii and Ophiostoma minus, over a range of temperatures. Under field conditions the woodwasp was able to detect and avoid ovipositing in P. sylvestris inoculated with L. wingfieldii, but its oviposition was unaffected by O. minus. My results show that insects co-habiting pine with S. noctilio have potential to exert a measure of biological control on the woodwasp and may help to limit its impact in North America.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 89-100). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 89-100). Also available on the Internet.

Thesis (Ph. D.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Plant Pathology, 1965. / Typescript. Includes bibliographical references.

Thesis (Ph.D.)--Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (p. 199-210).

The basidiomycetous yeast Malassezia has been linked to a number of disease states such as seborrhoeic dermatitis, dandruff and pityriasis versicolor. Much confusion has arisen as to its role in these disease states as this fungus is found inhabiting the stratum corneum of approximately 90% of the human adult population. Malassezia yeasts are lipophilic organisms, some species showing a specific requirement for long chain fatty acids for in vitro culture. The object of the experiments undertaken in this study was to elucidate the role of Malassezia yeasts in dandruff and seborrhoeic dermatitis.

The antibiotic, 2,4-diacetylphloroglucinol (Phl), is produced by a range of naturally isolated fluorescent pseudomonads, found in disease suppressive soils. The natural isolate, P. fluorescens F113, protects pea plants from the pathogenic fungus, Pythium ultimum, by reducing the number of pathogenic lesions on the plant's roots. This beneficial effect was however, outweighed by the F113 causing an overall reduction in the emergence of the pea plants in the infected soil. The gene locus responsible for the Phl production was shown to be functionally conserved between the P. fluorescens F113 and another Phl producing organism, P. fluorescens Q2-87. Following identification of this functional sequence homology, the genes were isolated from F113, by optimised, long PCR. The 6.7-kb gene cluster was inserted into the chromosome of a non-pathogenic P. fluorescens, SBW25, which can effect biological control against the plant pathogen, Pythium ultimum through competitive exclusion of the fungus, by means of its strong colonising competence. The insertion was a targeted, homologous recombination designed to insert the Phl coding genes, from the F113, into a non-essential, lacZY coding region of the SBW25 chromosome. The transformed strains of SBW25 assumed two different morphological appearances. The morphological changes were noted at a ratio of 1:1 of normal morphology and altered morphology. Transformation of SBW25 with the Phl locus without this repressor element led to transformants with only normal morphology. All transformants were able to suppress P. ultimum through antibiotic production following the Phl transformation. However, the fitness of the transformants was reduced in flask culture, at 30°C, against the un-transformed SBW25. The organisms transformed with the entire Phl locus were seen to clump together in the culture media. The strain transformed with the Phl locus lacking the repressor element behaved normally. When inoculated on pea seedlings, the strain containing no repressor element behaved similarly to the F113, causing lower pea seed emergence. A transformant containing the entire Phl genetic locus had not lost its environmental competence on the pea roots, maintaining a high population, but was unable to maintain a high population in the surrounding soil.

Made available in DSpace on 2014-06-11T19:26:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-27Bitstream added on 2014-06-13T20:33:54Z : No. of bitstreams: 1 pereira_fd_me_jabo.pdf: 415622 bytes, checksum: 3ed753ebff04eb379e6987cc2a0756c8 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A citricultura brasileira representa um importante segmento econômico na pauta de produtos agrícolas, não só por seu expressivo valor de produção, como por sua importância na geração de empregos diretos e indiretos. No mundo, o Brasil destaca-se como maior produtor de citros, e exportador de suco concentrado de laranja. Entretanto, a citricultura ressente-se de problemas complexos, de natureza diversa, com particular destaque para o de ordem fitossanitária. Dentre esses problemas destaca-se a Mancha Preta dos Citros (MPC), causada pelo fungo Guignardia citricarpa. A doença deprecia os frutos para o mercado in natura e restringe a possibilidade de exportação. Além disso, provoca a queda prematura dos frutos e eleva o custo de produção devido à necessidade de controle. O presente trabalho teve o objetivo de estabelecer relações filogenéticas entre Citrus spp. e Guignardia spp., entender a origem evolutiva do patossistema Citrus – G. citricarpa, bem como avaliar a ocorrência de G. citricarpa como patógeno em momentos distintos na história evolutiva de Citrus. Os dados filogenéticos foram gerados utilizando-se marcadores moleculares do tipo AFLP e sequenciamento da região ITS1-5.8S-ITS2, em ambos os gêneros. As análises filogenéticas foram realizadas no programa PAUP* v.4.0b10. Os resultados das análises filogenéticas utilizando AFLP foram mais informativos que aqueles gerados com base no sequenciamento da região ITS1-5.8S-ITS2, tanto para Citrus quanto para Guignardia. As análises de AFLP permitem concluir que G. citricarpa e G. mangiferae, isoladas de C. medica, apresentam maior distância filogenética em relação aos isolados das outras espécies cítricas. A evolução do patossistema Citrus/Guignardia não pôde ser estabelecida, de forma geral, por meio da associação das filogenias... / The Brazilian citriculture represents an important economic sector in the agenda of agricultural products, not only for its impressive production value, for its importance in generating direct and indirect jobs. In the world, Brazil stands out as the largest citrus producer and exporter of concentrated orange juice. However, the citriculture suffers from complex problems of diverse nature, with particular emphasis on plant health. Among these problems highlight the Black Spot of Citrus (BSC), caused by the fungus Guignardia citricarpa. The disease depreciates the fruit for the fresh market and restricts the ability to export. Furthermore, causes the fall premature fruit and raises the cost of production due to need for control. This study aimed to establish phylogenetic relationships between Citrus and Guignardia, understanding the evolutionary origin of pathosystem Citrus - G. citricarpa, and to evaluate the occurrence of G. citricarpa pathogen at different period in evolutionary history of Citrus. The phylogenetic data were generate for both genera using AFLP molecular markers and ITS1-5.8S-ITS2 sequencing . Phylogenetic analysis were performed in the PAUP * v.4.0b10 program. The phylogenetic analysis using AFLP were more informative than ITS1-5.8S-ITS2 sequencing in both genera Citrus and Guignardia. The AFLP analysis conclude that G. citricarpa and G. mangiferae isolated from C. medica presents a larger phylogenetic distance if compared to the other citrus spp. strains. The evolution of the pathosystem Citrus/Guignardia could not be established, in general, through the association of phylogenies generated for Citrus spp. and Guignardia spp. except in the particular case of bo isolated from C. medica, which follow a pattern of associations in pathogen/endophyte

Orientador: Silvana Giuliatti / Banca: Ana Lilia Alzate Marin / Banca: Gabriella Souza Cintra / Resumo: A citricultura brasileira representa um importante segmento econômico na pauta de produtos agrícolas, não só por seu expressivo valor de produção, como por sua importância na geração de empregos diretos e indiretos. No mundo, o Brasil destaca-se como maior produtor de citros, e exportador de suco concentrado de laranja. Entretanto, a citricultura ressente-se de problemas complexos, de natureza diversa, com particular destaque para o de ordem fitossanitária. Dentre esses problemas destaca-se a Mancha Preta dos Citros (MPC), causada pelo fungo Guignardia citricarpa. A doença deprecia os frutos para o mercado in natura e restringe a possibilidade de exportação. Além disso, provoca a queda prematura dos frutos e eleva o custo de produção devido à necessidade de controle. O presente trabalho teve o objetivo de estabelecer relações filogenéticas entre Citrus spp. e Guignardia spp., entender a origem evolutiva do patossistema Citrus - G. citricarpa, bem como avaliar a ocorrência de G. citricarpa como patógeno em momentos distintos na história evolutiva de Citrus. Os dados filogenéticos foram gerados utilizando-se marcadores moleculares do tipo AFLP e sequenciamento da região ITS1-5.8S-ITS2, em ambos os gêneros. As análises filogenéticas foram realizadas no programa PAUP* v.4.0b10. Os resultados das análises filogenéticas utilizando AFLP foram mais informativos que aqueles gerados com base no sequenciamento da região ITS1-5.8S-ITS2, tanto para Citrus quanto para Guignardia. As análises de AFLP permitem concluir que G. citricarpa e G. mangiferae, isoladas de C. medica, apresentam maior distância filogenética em relação aos isolados das outras espécies cítricas. A evolução do patossistema Citrus/Guignardia não pôde ser estabelecida, de forma geral, por meio da associação das filogenias... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Brazilian citriculture represents an important economic sector in the agenda of agricultural products, not only for its impressive production value, for its importance in generating direct and indirect jobs. In the world, Brazil stands out as the largest citrus producer and exporter of concentrated orange juice. However, the citriculture suffers from complex problems of diverse nature, with particular emphasis on plant health. Among these problems highlight the Black Spot of Citrus (BSC), caused by the fungus Guignardia citricarpa. The disease depreciates the fruit for the fresh market and restricts the ability to export. Furthermore, causes the fall premature fruit and raises the cost of production due to need for control. This study aimed to establish phylogenetic relationships between Citrus and Guignardia, understanding the evolutionary origin of pathosystem Citrus - G. citricarpa, and to evaluate the occurrence of G. citricarpa pathogen at different period in evolutionary history of Citrus. The phylogenetic data were generate for both genera using AFLP molecular markers and ITS1-5.8S-ITS2 sequencing . Phylogenetic analysis were performed in the PAUP * v.4.0b10 program. The phylogenetic analysis using AFLP were more informative than ITS1-5.8S-ITS2 sequencing in both genera Citrus and Guignardia. The AFLP analysis conclude that G. citricarpa and G. mangiferae isolated from C. medica presents a larger phylogenetic distance if compared to the other citrus spp. strains. The evolution of the pathosystem Citrus/Guignardia could not be established, in general, through the association of phylogenies generated for Citrus spp. and Guignardia spp. except in the particular case of bo isolated from C. medica, which follow a pattern of associations in pathogen/endophyte / Mestre