Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 112-131) Also available online.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 125-134).

Th. 3e cycle--Microbiol.--Toulouse 3, 1982. N°: 2653.

A cultura da batata (Solanum tuberosum L.) é a terceira fonte principal de alimento humano do mundo, posteriormente ao trigo e arroz. No Brasil, é a olerícola com maior área plantada e gera cerca de 160 mil empregos diretos e indiretos. A batateira é afetada por doenças transmitidas por patogénos do solo, ocasionando a migração da cultura para áreas nunca cultivadas ou sem o plantio de Solanaceae de dois a cinco anos consecutivos. A murcha bacteriana, causada pelo complexo de bactérias da Ralstonia spp., é uma das principais doenças que afetam a cultura da batata no mundo. No Brasil, o sistema convencional de produção de batata, adotado em quase totalidade nacional, gera condições ambientais ideias para a proliferação e desenvolvimento do complexo da Ralstonia ssp.. Dessa forma, precisam ser estudados sistemas alternativos de produção que reduzam a incidência de murcha bacteriana e cessem a migração contínua da cultura da batata. O aumento da biodiversidade e abundância dos microrganismos no solo é capaz de suprimir a ação dos patógenos nativos do solo. Para isso, são necessárias práticas de manejo que aumentem ou mantenham a matéria orgânica do solo, como a rotação e sucessão de culturas. O objetivo deste trabalho foi avaliar a capacidade supressiva do solo à murcha bacteriana nos sistemas alternativos de produção de batata, Paces e orgânico, em comparação ao sistema convencional, sistema não-perturbado sob vegetação natural e solo esterilizado. O delineamento experimental foi em blocos ao acaso, com três repetições, em esquema fatorial 4 x 4 + 1; o primeiro fator representou os solos sob diferentes sistemas de produção, enquanto o segundo correspondeu às doses de 0,25, 50 e 75% de solo contaminado com R. solanacearum adicionadas a cada tratamento. O tratamento adicional constituiu-se do solo do sistema convencional com alta incidência de R. solanacearum. Concluiu-se que a dose de 75% foi a que melhor representou a capacidade supressiva do solo à murcha bacteriana para todos os tratamentos. Nessa dose, as maiores incidências de plantas com sintomas de murcha foram para os solos autoclavado e convencional, que não diferiram entre si. O Sistema Paces, dentre todos os estudados, foi o que apresentou maior potencial de supressividade do solo à murcha bacteriana na batateira. / The potato crop (Solanum tuberosum L.) is the third most important source of human food in the world, after wheat and rice. In Brazil, it is the vegetable with largest area of growing and generates about 160 thousand direct and indirect jobs. The potato is affected by diseases transmitted by soil pathogens, causing the migration of the crop to areas never cultivated or without Solanaceaes from two to five consecutive years. The bacterial complex of Ralstonia spp., is one of the major diseases affecting the potato culture in the world. In Brazil, the conventional system of potato production, adopted in almost national conditions, promotes environmental conditions for the proliferation and development of the Ralstonia ssp. complex. In this way, alternative systems of production that reduce the incidence of bacterial wilt and decrease the intensity of the culture should be studied. Increased biodiversity and abundance of microorganisms in the soil is capable of suppressing an action of native soil pathogens. For this, management practices are applied that increase or decrease the production of soil extracts and of expression in bacteria in the alternative systems of production of potatoes, Paces and organic, were compared to conventional, unperturbed system in natural vegetation and sterilized soil. The experimental design was a randomized block design with three replications, in a 4 x 4 + 1 factorial scheme, the first factor represented the soils under different systems of production, while the second corresponded to the doses of 0.25, 50 and 75% of soil contaminated with R. solanacearum added to each action. The additional was conventional soil with high incidence of R. solanacearum. It was concluded that a dose of 75% was the one that best represented a suppressiveness capacity of the soil to bacterial wilt in all the treatments, to the extent that the incidence of plants with wilt were for the treatments of autoclaved and conventional soil, that did not differ each other. The Paces System, was the one that had the greater potential of soil suppressiveness to the bacterial wilt in the potato.

published_or_final_version / abstract / Biological Sciences / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 110-118).

Ralstonia solanaearum, a soil borne pathogen infects several important crops causing wilting. In 2000-2001, two eucalyptus isolates, BCCF 401 and BCCF 402 were isolated from plantations in Kwa-Zulu Natal and the Democratic Republic of Congo, respectively. Arabidopsis has been recognised as a host for R. solanacearum and as such has been adopted as a model to understand the plant defence response against this pathogen. The aim of this study was to use microarray expression profiling techniques to elucidate the plant defence response and to identify candidate genes possibly contributing towards resistance against the pathogen. As a means to optimise microarray expression profiling, the differential expression in an Arabidopsis mutant, cir1 (constitutively induced resistance 1) and wild-type plants was investigated using a custom 500-probe microarray. Several genes were found to be induced in cir1 at a significance threshold of –log10(p) equal to 3 (p< 0.001) using a mixed model ANOVA approach. The genes AtACP1 (sodium inducible calcium binding protein), AtP2CHA (protein phosphatase 2C), AtGSTF7 (glutathione S transferase), tryptophan synthase betalike and AtPAL1 (phenylalanine ammonia lyase 1), AtEREBP-4 (ethylene response element binding protein 4) and HFR1 (long hypocotyl in far-red 1) were further identified as possible candidate genes which may contribute to disease resistance in cir1 against Pseudomonas syringae pv. tomato. A similar transcript profiling approach, using the optimised protocols, was adopted to investigate the compatible interaction between Arabidopsis ecotype Col-5 and the R. solanacearum isolate BCCF 401. A screen of 5000 Arabidopsis ESTs revealed approximately 120 genes differentially regulated by R. solanacearum infection at a significance threshold of p<0.03 (Bonferroni corrected). Subsequent bioinformatic comparisons revealed that abscisic acid responses appear to be induced in Col-5 in response to the pathogen and that R. solanacearum induces an expression profile consistent with a necrotroph. The basal defence responses in Col-5 against R. solanacearum infection were investigated by comparing the expression data to that during treatment with the pathogen associated molecular patterns (PAMPs) flg22 and lipopolysaccharide, and the Type Three Secretion System deficient Pst hrp- mutant. Expression patterns for a subset of these genes were suggestive of host basal defences manipulated by the pathogen. It is hypothesised that genetic engineering to alter the expression of these “pathogen-manipulated” genes could contribute to resistance against R. solanacearum in the host. Copyright 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Naidoo, S 2008, Microarray expression studies in the model plant Arabidopsis thaliana infected with the bacterial pathogen Ralstonia solanacearum, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11182008-092625 / > D559/gm / Thesis (PhD)--University of Pretoria, 2008. / Plant Science / unrestricted