Made available in DSpace on 2014-06-11T19:28:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-17Bitstream added on 2014-06-13T20:18:13Z : No. of bitstreams: 1 gomes_dp_me_jabo.pdf: 375333 bytes, checksum: d2044e94be55c12e13ab4e37ad5eb7ea (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo da pesquisa foi determinar a influência de fatores abióticos e bióticos sobre a ocorrência de “damping-off” de pré e de pós – emergência, além de outros danos nas sementes e plântulas, quando da semeadura de milho e feijão. Foram escolhidos dois lotes de milho e feijão, safra 2007/2008, provenientes das cultivares D 766 e Carioca, respectivamente, de acordo com sua distinção em alto e baixo vigor, com baixa incidência fúngica e ausência de Rhizoctonia solani. Sementes desinfestadas foram infectadas com o fungo em meio de cultura BDA com restrição hídrica (acrescido de manitol a -1,0 MPa). Nos tratamentos testemunha foi utilizado o mesmo meio de cultura, porém, sem a presença do fungo. Para cada tratamento as sementes foram sobrepostas nos meios de cultura por 36 horas para o milho e por 20 horas para o feijão. Para a infestação direta do fungo em solo, foram utilizadas sementes de sorgo esterilizadas. O experimento foi conduzido em duas épocas distintas (caracterizadas como fria e quente). Para as duas épocas, as parcelas experimentais foram constituídas de vasos plásticos (capacidade de 4,5 L) contendo terra esterilizada dispostos segundo a casualização dos tratamentos em casa de vegetação. Os tratamentos foram constituídos a partir de três disponibilidades hídricas no solo contido em vaso (30 %, 50 % e 70 % de retenção de água), dois níveis de vigor da semente (alto e baixo vigor) com e sem a inoculação de Rhizoctonia solani, através de inoculação na própria semente do hospedeiro e da infestação no solo através de sementes de sorgo esterilizadas. Foram feitas quatro repetições, cada uma contendo dois vasos, totalizando oito vasos para cada tratamento. / The objective of the research was to determine the influence of biotic and abiotic factors on the occurrence of damping-off of pre and post - emergence, and others problems to the seeds and seedlings, when the sowing of corn and bean. They chose two plots of corn and bean, growing season 2007/2008, from the cultivars Carioca and D 766 respectively, according to his distinction in high and low vigour, low fungi incidence and absence of Rhizoctonia solani. Disinfested seeds were infected with the fungus in culture medium without BDA and water restriction (mannitol, -1.0 MPa). In control treatments was the same growing medium, but without the presence of the fungus. For each treatment the seeds were superimposed in culture media for 36 hours for the corn and bean for 20 hours. For the direct addition of the fungus in soil, we used the technique of sterile sorghum seeds. The experiment was conducted in two different seasons (hot and cold). For two growing seasons the plots were established in plastic pots (capacity 4.5 L) containing sterilized soil prepared according to the randomization of treatments in a greenhouse. The treatments were made from three water availability in the soil contained in vase (30 %, 50 % and 70 % retention of water), two levels of vigour of the seed (high and low vigour) with and without inoculation of Rhizoctonia solani by of inoculation in the seed of the host and soil addition with sterile sorghum seeds. Were four replicates, each containing two vessels, totaling eight pots for each treatment. Twenty days after inoculation, for the cold season, and fifteen days for the hot season was to assess the severity, damping-off of pre and post-emergence, seedling length, dry matter weight and percentage of seedlings healthy.

Made available in DSpace on 2015-03-26T13:51:56Z (GMT). No. of bitstreams: 1 01 - capa_abstract.pdf: 60769 bytes, checksum: 7bb9d45d4373809fdd703200fc0ce609 (MD5) Previous issue date: 2006-10-03 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / In nature, species of Orchidaceae are always associated with mycorrhizal fungi. However, diversity of fungi associated to the orchids is little studied. Fungus-plant specificity has been observed and its comprehension is very important to establish programs for the simbiotic propagation of orchids. The objective of this work was to study the diversity and specificity of Rhizoctonia-like fungi associated to four populations of Epidendrum secundum, growing at three localities in the Totem Deitado Mountain, at State Park of Serra do Brigadeiro, in Minas Gerais. Segments of healthy roots were collected from two populations growing at campo garminóide , near rocky outcrop, and another one growing at campo garminóide by a escrube area, localized at 1700 m above the sea level, and the last was growing at campo graminóide on a rocky outcrop, localized at 1580 m of altitude. Twenty six isolates, all belonging to the Epulorhiza, were obtained by transferring cortical root fragments to the isolation medium. In general, the colony aspect of the isolates, the morphology, and width of monilioid cells were different among isolates from different localities, but similar in the population. The multivariate analyses of morphological characteristics using Tocher optimization, UPGMA, and graphic dispersion by canonic variables, separated the 26 isolates in, respectively, six, two, and three groups, showing similarities among most of all isolates from population I, II, and IV, and, also, among isolates from population III, and M61, from population II. Epulorhiza spp., isolated from E. secundum, supported seed germination of this plant species, but efficiency to promote protocorm development varied even among the isolates that presented morphological similarities. Results from this work show that there is high diversity of mycorrhizal fungi in Epulorhiza associated to E. secundum in this region and confirm the high specificity of this orchid to this fungal genus. / Na natureza, as espécies da família Orchidaceae estão associadas a fungos micorrízicos, entretanto, a diversidade de fungos associados às orquídeas é ainda pouco conhecida. Especificidade nessa associação fungoplanta vem sendo observada, sendo sua compreensão fundamental para o desenvolvimento de programas para propagação simbiótica das orquídeas. O objetivo deste trabalho foi estudar a diversidade e a especificidade de fungos micorrízicos rizoctonióides associados a quatro populações de Epidendrum secundum crescendo em três locais de um campo de altitude localizado na sub-serra Totem Deitado, no Parque Estadual da Serra do Brigadeiro, em Minas Gerais. Raízes saudáveis foram coletadas de duas populações crescendo sobre campo graminóide próximo a afloramento rochoso e uma sobre campo graminóide próximo a escrube, em altitude aproximada de 1700 m, e a última em uma pequena mancha de campo graminóide sobre afloramento rochoso, em altitude aproximada de 1580 m. Vinte e seis isolados fúngicos, todos pertencentes ao gênero Epulorhiza, foram obtidos a partir da transferência asséptica de fragmentos do tecido cortical de raiz colonizada para o meio de isolamento. De modo geral, os aspectos da colônia dos isolados, a morfologia e a largura das células monilióides evidenciaram diferenças entre os fungos isolados de diferentes locais, mas semelhanças foram observadas entre aqueles isolados de um mesmo local. A análise de agrupamento utilizando as características morfométricas, pelas técnicas de otimização de Tocher, UPGMA e de dispersão gráfica pelas variáveis canônicas separaram os 26 isolados em, respectivamente, seis, dois e três grupos, evidenciando as semelhanças entre a maioria dos isolados da população I, II e IV, e também entre os isolados da população III e o isolado M61 da população II. Os fungos Epulorhiza spp., isolados de E. secundum, induzem a germinação das sementes desta planta, mas apresentam diferenças na eficiência em promover o desenvolvimento dos protocórmios, mesmo entre os fungos que apresentam grandes semelhanças morfológicas. Os resultados deste trabalho mostram existir uma grande diversidade de fungos micorrízicos do gênero Epulorhiza associados a E. secundum nesta região e confirmam a existência da especificidade entre esta espécie de orquídea e este gênero de fungo.

Resumo: A mancha areolada causada por Thanatephorus cucumeris, é uma das doenças mais importantes da seringueira (Hevea brasiliensis) na região Amazônica. Apesar disso, há pouca informação disponível sobre a diversidade biológica, patogênica e genética do patógeno. Uma questão importante sobre o real posicionamento filogenético deste patógeno ainda não foi respondida. Neste estudo, foram analisadas seqüências da região ITS-5.8S do rDNA de uma população de T. cucumeris (fase anamórfica = Rhizoctonia solani AG 2-2) associado à mancha areolada da seringueira, obtida em Belém (PA), Manaus (AM) e Xapuri/Rio Branco (AC). Esta população foi também comparada filogeneticamente com membros do AG 2 descritos mundialmente. Este estudo representa um passo importante para revelar a origem, os padrões de movimento e amplificação de genótipos epidemiologicamente importantes de T. cucumeris da seringueira. Filogenéticamente, através de análise Bayesiana e de máxima parcimônia, encontramos suporte para nomear um novo grupo de anastomose associado à mancha areolada da seringueira: o AG 2-2 Hb. Este grupo constitui-se numa unidade evolucionária independente em relação aos subgrupos mundiais do AG 2-2 analisados. Na genealogia construída por análise coalescente, observou-se que a população de R. solani AG 2-2 Hb, de Belém, é relativamente mais velha que as demais populações analisadas. O ancestral comum de todas as três populações analisadas está associado com a mancha foliar do maracujazeiro (Passiflora edulis), em Belém, e tem cerca de 0,8 unidades evolucionárias coalescentes de idade. Nenhum haplótipo da região ITS-5.8S do AG 2-2 Hb, de Belém, foi observado em outras regiões. Entretanto, a população de Manaus compartilhou dois, de seus quatro haplótipos, com aqueles observados em Xapuri / Rio Branco, no Acre, indicando fluxo gênico e deriva genética. / Abstract: Thanatephorus leaf spot is one of the most important diseases of rubber tree (Hevea brasiliensis) in the Amazon region, Brazil. However, there is fill information available about the biological, pathogenic and genetic diversity of the pathogen. An important question about the actual phylogenetic placement of this pathogen is not answered yet. In this study, we analyzed sequences of the ITS-5.8S rDNA region from a population of T. cucumeris (anamorphase = Rhizoctonia solani AG 2-2) associated to the rubber tree leaf spot obtained in Belém (PA), Manaus (AM) and Xapuri/Rio Branco (AC). This population was also phylogenetically compared with members of AG 2 world-widely described. This study represents an important step to reveal the origin, the patterns of movement and amplification of epidemiologically important genotypes of rubber tree-infecting T. cucumeris. Phylogenetically, through both Bayesiana and maximum parsimony analyses, we found support to nominate a new group of anastomosis associated with the rubber tree foliar spot: the AG 2-2 Hb. This group consisted of a independent evolutionary unit in relation to the world-wide sub-groups of AG 2-2 analyzed. In the gene genealogy built by coalescent analysis, was observed that the population of R. solani AG 2-2 Hb of Belém is relatively older than the other populations analyzed. The oldest most recent common ancestor of all the three populations analyzed was associated with a sample obtained from passion-fruit (Passiflora edulis) leaf blight in Belém and has about 0.8 coalescent evolutionary units of age. No AG 2- 2 Hb ITS-5.8S rDNA haplotype from Belém was observed in any other regions. However, the population from Manaus shared two, of its four haplotypes, with those observed in Xapuri/Rio Branco (Acre), indicating both gene flow and genetic drift. / Orientador: Paulo Cezar Ceresini / Coorientador: Alcebíades Ribeiro de Campos / Banca: Cesar Junior Bueno / Banca: Edson Luiz Furtado / Mestre

Na natureza, as orquídeas são totalmente dependentes de fungos micorrízicos para germinar. Estes fungos podem penetrar nas células das raízes e formar pélotons, os quais, quando digeridos pela planta, providenciam açúcares simples para o embrião. Durante a fase aclorofilada de desenvolvimento da plântula, orquídeas são obrigatoriamente dependentes dos fungos; algumas continuam assim por toda vida enquanto outras se tornam facultativamente responsivas à colonização. O objetivo deste trabalho foi identificar quantos clados de fungos podem estabelecer associação micorrízica com Coppensia doniana (sin. Oncidium donianum), uma orquídea amplamente distribuída nos arredores de Campos do Jordão e, demonstrar como as características morfológicas dos isolados, quando analisadas com ferramentas de estatística multivariada, podem ser úteis para a taxonomia destes fungos. Dez plantas foram amostradas em um sítio com vegetação típica de campos de altitude, junto ao Parque Estadual de Campos do Jordão. Fungos foram isolados pela transferência asséptica de cortes de raízes contendo pélotons para meios de cultura BDA modificados. Três clados de fungos foram formados, tanto analisando as características qualitativas das culturas quanto as quantitativas. Os clados foram identificados como dois morfotipos do gênero Ceratorhiza (fase anamórfica de Ceratobasidium) e uma Rhizoctonia-uninucleada. O sequenciamento da região ITS produziu resultados idênticos a estes, mostrando os mesmos três clados. Todas as sequências tiveram alta correlação com sequências de Ceratobasidium depositadas no Genbank, o que sugere uma alta afinidade de Coppensia doniana com este gênero. Também ficou demonstrado que os dados morfológicos, quando associados à estatística multivariada são uma ferramenta útil na taxonomia polifásica de Rhizoctonia spp. As sequências dos isolados de Coppensia doniana também foram comparadas com as de isolados de outras orquídeas, dentro da subtribo Oncidiinae, incluindo: Ionopsis utricularioides e Psygmorchis pussila, coletadas na região do Valle del Cauca Colômbia e isolados de 10 Ionopsis utricularioides, Oncidium altissimum e Tolumnia variegata, estudados por Otero (2002, 2004, 2007), em diferentes regiões de Porto Rico, Costa Rica, Cuba e Panamá. Esta última análise veio a comprovar a preferência de orquídeas da subtribo Oncidiinae por fungos do gênero Ceratobasidium, apesar de que os clados obtidos no Brasil e na Colômbia foram distantes filogeneticamente dos clados previamente estudados na América Central. Representantes dos três clados obtidos de C. doniana em Campos do Jordão foram também testados quanto à capacidade de induzir germinação em suas sementes. Todos isolados testados tiveram sucesso na germinação das sementes, levando as plântulas a estádios avançados de desenvolvimento após 30 dias, o que indica um alto potencial para utilização biotecnológica destes isolados para a germinação das sementes destas orquídeas, tanto para a floricultura comercial quanto para programas de reintrodução de espécies de orquídeas ameaçadas de extinção. / In nature, orchids are fully dependent on mycorrhizal fungi for germination. These fungi can penetrate root cells and form pelotons, whose digestion provides simple sugars for the embryo. During the achlorophyllous seedling stage, orchids are obligatory dependent on the fungi, and some species remain so through life, while others become facultatively responsive to fungal infection. The aim of this study was to identify how many fungal clades can establish mycorrhizal associations with Coppensia doniana, a widespread orchid from Campos do JordãoBrazil, and to demonstrate how their morphological features, analyzed with multivariate statistics, can be useful for classification. Ten plants were sampled in an Araucaria forest near Campos do Jordão. Fungi were isolated by transferring surface disinfected root segments containing pelotons to PDA culture medium. Three main fungal clades were formed by qualitative and quantitative morphological data. They were identified as two morphotypes of Ceratorhiza (anamorphic stage of Ceratobasidium) and one uninucleated Rhizoctonia. The ITS sequencing corroborates this identification, since the same three clades were found. All sequences were highly correlated to Ceratobasidium ITS data deposited at the Genebank, suggesting a high affinity between this species of Oncidiinae and Ceratobasidium. It also could be shown that morphological data associated with multivariate statistics can be a useful tool in fungal multi-level taxonomy. C. doniana sequences were also compared to sequences obtained from isolates of other orchids, belonging to the sub-tribe Oncidiinae, including: Ionopsis utricuarioides and Psygmorchis pussila, collected in Valle del Cauca Colombia and isolated from I. utricularioides, Oncidium altissimum and Tolumnia variegata, studied by Otero (2002, 2004, 2007) in different regions of Puerto Rico, Costa Rica and other Caribbean islands. This last analysis confirmed the preference of this Oncidiinae sub-tribe for Ceratobasidium, although isolates obtained in Brazil or Colombia belong to different clades from those previously studied in Puerto Rico, Costa Rica, Panama and Cuba. 12 Fungi representing the three clades obtained from C. doniana in Campos do Jordão were also tested for their ability to induce germination of C. doniana seeds, with a positive response for all of them, being able to bring the seedlings to advanced development stages in 30 days. These results suggest a high biotechnological potential of these isolates, to be used in orchid symbiotic germination for commercial flower production or for the reintroduction of endangered Brazilian orchid species.

La presente investigación se realizó con el fin de evaluar el uso de biocontroladores en la prevención de patógenos causantes de camping off y en el desarrollo de plantines de tomate, aplicados en un sustrato obtenido de material orgánico bioprocesado.

Rhizoctoniasis of potato occurs in all regions of the world where the crop is grown. The disease is caused by various anastomosis groups (AGs) of the fungus Rhizoctonia solani, of which AG-3 is the most common. Very little information is available on the AGs involved in potato rhizoctoniasis in South Africa. This study elucidated the etiology of the disease in the country and also provided guidelines regarding alternative control strategies. The vast majority (99.3 %) of R. solani isolates from symptomatic potato tubers collected at seven of the 14 potato production regions in South Africa belonged to AG-3, and 0.7 % to AG-5. Of the isolates from infected stems and roots, 82.1 % were AG-3, 12.8 % AG-4, and 5.1 % AG-5. Isolations from soil yielded 67.7 % AG-3, 22.0 % AG-4, 5.5 % AG-5, and 2.4 % of each of AG-7 and AG-8. In vitro screening indicated that AG-3 isolates were the most virulent. The progeny of seed tubers naturally infected with R. solani was rendered free of infection by dipping the tubers in hot water at 55 C for 8 minutes, 60 ºC for 6 minutes, or 65 ºC for 4 minutes. However, treatments more severe than 55 ºC for 8 minutes progressively increased tuber mortality. OA5 DP, an organic tin complex, proved to be the most effective of 20 disinfectants for killing sclerotia of the pathogen on seed tubers and rendering the progeny free of infection, but exhibited acute phytotoxicity towards the tubers. Significant control without any phytotoxicity was achieved with the didecyl ammonium chloride compound, Sporekill. Tolclofos-methyl was the only fungicide that provided total control of potato rhizoctoniasis, whereas seed tuber treatment with fludioxonil, kresoxim-methyl and metam-sodium significantly reduced disease in the progeny. Incorporation of of the biocontrol formulation TrykocideTM (Trichoderma harzianum) into soils artificially infested with R. solani AG-3 eradicated the pathogen. Significant reductions in pathogen populations were also evident in soils amended with azoxystrobin, kresoxim-methyl, MaxifloTM Azospirillum brasilense), AvogreenTM (Bacillus subtilis), cattle, chicken and sheep manure, citrus and mango waste compost, composted kraal manure, and shoot tissues of Brassica napus, B. oleracea var. capitata, Raphanus sativus, Sinapsis alba and Tagetes minuta. TrykocideTM provided total control of stem canker in artificially infested soil, whereas kresoxim-methyl, azoxystrobin, sheep manure, B. napus and B. oleracea var. capitata shoot tissue, mango waste compost, and the systemic resistance-inducing compound, acibenzolar-s-methyl, reduced the disease significantly. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Rhizoctonia blight (sensu lato) is a common and serious disease of many turfgrass species. The most widespread causal agent R. solani consists of several genetically different anastomosis groups (AGs) and subgroups. Though anastomosis or hyphal fusion reactions have been used to group Rhizoctonia species, they are time consuming and sometimes difficult to interpret. Anastomosis reactions are incapable of identifying isolates belonging to different AG subgroups within an AG. This study evaluated molecular techniques in comparison with traditional anastomosis grouping (AG) to identify and group isolates of Rhizoctonia. More than 400 Rhizoctonia isolates were collected from diseased turfgrass leaves from eight geographic areas in Virginia and Maryland. A random sample of 86 isolates was selected and initially characterized by colony morphology, nuclei staining and anastomosis grouping. Molecular identification was performed by analysis of rDNA-ITS region and DNA fingerprinting techniques universally primed PCR (UP-PCR) and amplified fragment length polymorphism (AFLP). The cladistic analysis of ITS sequences and UP-PCR fragments supported seven clusters. Isolates of R. solani AG 1-IB (n=18), AG 2-2IIIB (n=30) and AG 5 (n=1) clustered separately. Waitea circinata var. zeae (n=11), and var. circinata (n=4) grouped separately. A cluster of six isolates (UWC) did not fall into any known Waitea group. Most of the binucleate Rhizoctonia-like fungi (BNR) (n=16) grouped separately. AFLP grouping also largely agreed with the above results. However, UWC isolates clustered into two groups. Molecular analyses corresponded well with traditional anastomosis grouping by clustering isolates within an AG or AG subgroup together. UP-PCR cross-hybridization could distinguish closely related Rhizoctonia isolates to their infraspecies level. Genetically related isolates belonging to the same AG subgroups cross-hybridized strongly, while isolates of different AGs did not cross-hybridize or did so weakly. Sequence-characterized amplified region (SCAR) markers were generated from UP-PCR products to identify isolates of major pathogenic groups AG 1-IB and AG 2-2IIIB. Specific primer pairs successfully distinguished isolates of AG 1-IB and AG 2-2IIIB from isolates of other AGs. Sensitivity of Rhizoctonia species and AGs was tested in vitro to commercial formulations of iprodione, triticonazole and pyraclostrobin. W. circinata isolates were moderately sensitive to iprodione while isolates of R. solani and BNR were extremely sensitive. Isolates of AG 2-2IIIB showed less sensitivity to triticonazole than other Rhizoctonia isolates. W. circinata var. zeae isolates were moderately sensitive to pyraclostrobin while most of the other isolates were extremely sensitive. / Ph. D.

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Historically root diseases have been a production-limiting problem for the strawberry industry worldwide. In the Western Cape Province of South Africa the most serious root disease is black root rot, which causes losses of up to 30%, annually. The aims of this study were to investigate aspects of the etiology and epidemiology of this disease in the Western Cape, and to provide information that can be incorporated in an integrated disease management strategy. In Chapter I a summary of published information on this disease is presented. Disease symptoms include severe stunting of plants, which have black, rotted, reduced root systems. Even though this disease is of great economic importance, the etiology remains unresolved. However, soilborne fungal root pathogens, particularly Pythium and Rhizoctonia spp. have been implicated as major role players. Control of this disease, as well as the other root diseases affecting strawberries, has relied on soil fumigation with broad spectrum chemical fumigants, in particular methyl bromide. However, due to the ozone depleting action of methyl bromide it was decided at the signing of the Montreal Protocol to remove this chemical from the market. This action has caused great demand for alternative measures to control root diseases on many crops including strawberries. Development of integrated disease management strategies is dependent upon a more complete understanding of the etiology, biology and ecology of the disease complex. In Chapter 2 fungal pathogens associated with diseased plants were isolated and Koch's postulates were carried out. The most frequently isolated fungal pathogens were Pythium irregulare, Rhizoctonia spp. and Cylindrocarpon destructans. Two morphotypes of Rhizoctonia were isolated viz. a brown and a white type. Pythium irregulare was isolated more frequently in July than in September, and was not isolated at all in November. Rhizoctonia spp. were present at all sampling dates but were more frequently isolated in November than at the other times. All the fungi that were tested were pathogenic and caused root lesions. Cylindrocarpon destructans and Coniella fragariae did not have a stunting effect on the plants. These results confirm a major role for Pythium and Rhizoctonia in the black root rot complex and suggest that there is a complimentary seasonal variation in occurrence between these two pathogens. The Rhizoctonia species and anastomosis groups of isolates obtained from diseased strawberries in the Western Cape Province were determined, and their pathogenicity and relative virulence assessed. Both binucleate and multinucleate types were recovered from diseased roots and identified as R. fragariae and R. so/ani, respectively. All isolates of R. solani were members of anastomosis group (AG) 6, whereas three AG types were identified among isolates of R. fragariae, viz. AG-A, AG-G and AG-I at a relative occurrence of 69%, 25%, 6% respectively. All Rhizoctonia isolates were pathogenic to strawberry, but R. solani (AG 6) was the most virulent causing severe stunting of plants. This is the first species confirmation and AG type identification of Rhizoctonia taxa causing root rot of strawberries in South Africa. An assessment of the presence and quantity of black root rot pathogens associated with soils prior to fumigation and post fumigation with methyl bromide, was made in Chapter 4. Isolations were also made from nursery plants to determine whether any black root rot pathogens were in the plants before transplanting. Results demonstrated that after fumigation the soil was free of all pathogenic fungi associated with the disease. However, the main pathogens involved in black root rot, viz. Rhizoctonia fragariae, R. solani and Pythium spp. were isolated from nursery plants. The fact that the plants are already infected with these pathogens renders the prospects for control of this disease difficult. Further studies are urgently required to develop production practices that can be included in disease management programmes. In vitro studies were carried out to determine the ECso values of different fungicides for isolates of Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G and AG-I and R. solani AG 6. Benomyl, fludioxonil and tolc1ofos-methyl were used in these tests. Field trials were also conducted using these fungicides. In Chapter 5 it is shown that in general application of fungicides improved the yield and did not affect the survival rate of strawberry plants. Fludioxonil showed potential for short-term use. Applications of fungicides that targeted specific fungal genera were not sufficient to control the disease. Seasonal fluctuation of Pythium and Rhizoctonia spp. became apparent with the occurrence of Pythium being relatively high early in the season but low late in the season. Conversely, the occurrence of Rhizoctonia was low at the beginning of the season but high late in the season. In the short-term there is potential for fungicide applications as part of an integrated disease management strategy, but the economic feasibility of this practice needs to be assessed. In this study the major pathogens causing black root rot were identified in the Western Cape Province of South Africa, and important information regarding the epidemiology of the disease was reported. These results can be incorporated in an integrated management strategy to reduce losses of strawberry production, attJibutable to black root rot. / AFRIKAANSE OPSOMMING: Wortelsiektes is wêreldwyd 'n produksie-beperkende probleem vir die aarbeibedryf. . Swartwortelvrot, wat jaarliks verliese van tot 30% veroorsaak, is die belangrikste wortelsiekte in die Wes-Kaap Provinsie van Suid-Afrika. Die doelwitte van hierdie studie was om aspekte van die etiologie en epidemiologie van die siekte in die Wes- Kaap te ondersoek en inligting wat in geïntegreerde siektebestuurstrategië ingesluit kan word, te voorsien. In Hoofstuk 1 word 'n opsomming van gepubliseerde inligting aangaande die siekte uiteengesit. Siektesimptome sluit ernstige verdwerging van plante met swart verotte en verkleinde wortelstelsels in. Alhoewel die siekte van groot ekonomiese belang is, is die etiologie grootliks onbekend. Grondgedraagde wortelpatogene swamme, spesifiek Pythium en Rhizoctonia spp., is egter as belangrike rolspelers geïdentifiseer. Tot dusver het die beheer van hierdie siekte sowel as ander wortelsiektes van aarbeie berus op grondberoking met breë spektrum chemiese berokingsmiddels, spesifiek metielbromied. As gevolg van die osoonafbrekende aksie van metielbromied is daar egter tydens die ondertekening van die Montreal Protocol besluit om dié middel van die mark te verwyder. Hierdie besluit het 'n groot aanvraag na alternatiewe beheermaatreëls vir wortelsiektes van verskeie gewasse, insluitende aarbeie, veroorsaak. Die ontwikkeling van geïntegreerd siektebestuurstrategieë is egter afhanklik van 'n meer volledige begrip van die etiologie, biologie en ekologie van die siektekompleks. In Hoofstuk 2 is die patogene swamme wat met die siekte geassosieer word, geïsoleer, en is Koch se postulate uitgevoer. Die mees algemeen geïsoleerde patogene swamme was Pythium irregulare, Rhizoctonia spp. en Cylindrocarpon destructans. Twee morfotipes van Rhizoctonia is geïsoleer, nl. 'n bruin tipe en 'n wit tipe. Pythium irregulare is meer dikwels in Julie as in September geïsoleer, maar glad nie in November nie. Rhizoetonia het tydens alle monstertye voorgekom, maar is meer dikwels in November geïsoleer. Al die swamme wat getoets is, was patogenies en het letsels op die wortels veroorsaak. Cylindroearpon des true tans en Coniella fragariae het nie'n verdwergingseffek op plante gehad nie. Hierdie resultate bevestig die dominante rol van Pythium en Rhizoctonia in die swartwortelvrot kompleks en dui op 'n komplementêre seisoenale variasie in die voorkoms van hierdie twee patogene. Die Rhizoctonia spesies en anastomose groepe (AG) van die isolate geisoleer vanaf siek aarbeiplante in die Wes-Kaap Provinsie is bepaal, en die patogenisiteit en relatiewe virulensie is beraam. Sowel tweekernige as multikernige tipes is vanaf siek wortels geïsoleer en respektiewelik as R. fragariae en R. so/ani geïdentifiseer. Alle isolate van R. so/ani was lede van anastomose groep 6, terwyl drie AG tipes, nl. AGA, AG-G en AG-I onder die R. fragariae isolate geïdentifiseer is met relatiewe voorkomste van 69%, 25%, 6% respektiewelik. Alle Rhizoctonia isolate was patogenies op aarbeie, maar R. so/ani (AG 6) was die mees virulente en het ernstige verdwerging van plante veroorsaak. Hierdie is die eerste bevestiging van spesies en identifisering van AG tipes van Rhizoctonia taksa wat wortelvrot van aarbeie in Suid Afrika veroorsaak. In Hoofstuk 4 is 'n beraming van die voorkoms en hoeveelheid swartwortelvrot patogene geassosieer met grond voor, en na beroking met metielbromied, gemaak. Isolasies is ook vanaf kwekeryplante gemaak om te bepaal of enige swartwortelvrot patogene voor oorplanting in die plante teenwoordig was. Die resultate het getoon dat grond na beroking vry was van alle patogeniese swamme geassosieër met die siekte. Die hoof patogene betrokke in die swartwortelvrot kompleks, nl. Rhizoctonia fragariae, R. so/ani en Pythium spp. was egter in die kwekery plante teenwoordig. Die feit dat plante reeds met hierdie patogene geïnfekteer is, maak die vooruitsigte vir die beheer van hierdie siekte moeilik. Verdere studies word dringend benodig vir die ontwikkeling van produksiepraktyke wat by siektebestuursprogramme ingesluit kan word. In vitro studies om die ECso waardes van die isolate van Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G en AG-I en R. so/ani AG 6 vir die fungisiedes benomyl, fludioxonil en tolclofos-metiel te bepaal, is uitgevoer. Hierdie fungisiedes is ook in veldproewe getoets. In Hoofstuk 5 is getoon dat aanwending van fungisiedes die opbrengs verbeter het en nie die oorlewing van aarbeiplante beïnvloed het nie. Fludioxonil het potensiaal vir korttermyn gebruik getoon. Die aanwending van fungisiedes wat spesifieke swamgenera teiken, was nie voldoende om die siekte te beheer nie. Seisoenale fluktuasies van Pythium en Rhizoctonia spp. het duidelik geword met die relatief hoë voorkoms van Pythium vroeg in die seisoen, maar lae voorkoms laat in die seisoen, terwyl die voorkoms van Rhizoctonia laag was aan die begin van die seisoen, maar hoog later in die seisoen. In die korttermyn is daar potensiaal vir fungisiedtoedienings as deel van 'n geïntegreerde siektebestuurstrategie, maar die ekonomiese haalbaarheid van hierdie praktyk moet bepaal word. In hierdie studie is die hoof patogene wat swartwortelvrot van aarbeie in die Wes-Kaap Provinsie van Suid-Afrika veroorsaak geïdentifiseer, en belangrike inligting rakende die epidemiologie van die siekte is aangeteken. Hierdie resultate kan in 'n geïntegreerde bestuurstrategie geïnkorporeer word om verliese van aarbeiproduksie, toeskryfbaar aan swartwortelvrot te, verminder.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-16T12:53:24Z No. of bitstreams: 1 Eddy Enrique Barraza Andrion (1).pdf: 947495 bytes, checksum: aa5e0f6002d19bd71d54a71eae9dc237 (MD5) / Made available in DSpace on 2017-03-16T12:53:24Z (GMT). No. of bitstreams: 1 Eddy Enrique Barraza Andrion (1).pdf: 947495 bytes, checksum: aa5e0f6002d19bd71d54a71eae9dc237 (MD5) Previous issue date: 2009-07-31 / The cowpea (Vigna unguiculata L.) is one of the main crops in the Northeast of Brazil especially for the small farmers. The Fusarium wilt and Rhizoctonia canker caused by Fusarium oxysporum f.sp. tracheiphilum and Rhizoctonia solani, respectively are the cowpea diseases showing more frequency and intensity in the Northeast of Brazil. This work aimed to evaluate the natural suppressiveness of 66 soils of this region to the Fusarium wilt and Rhizoctonia canker, and to analyze the physical, chemical and biological characteristics of this soils associated with disease suppressiveness or conducivity. The evaluated soils were grouped from highly suppressive to highly conducive in relation to Fusarium wilt and Rhizoctonia canker severities. The main variables involved in Fusarium wilt suppressiveness were high levels of phosphorus and potassium, basal respiration (CO2 evolution) and indexes of microbial diversity and equitability. For Rhizoctonia canker important correlations were determined with levels of phosphorus, potassium and sodium, basal respiration and enzymatic activity of fluorescein diacetate. There was no correlation between physical factors and suppressiveness to Fusarium wilt, but it was possible to correlate the levels of sand, clay and silt with suppressiveness and/or conducivity of Rhizoctonia canker. Three soils previously classified as highly supressive to Rhizoctonia canker were evaluated in relation to eight strains and three inoculum densities of R. solani. There was significant difference among soils and strains in relation to levels of disease severity. In the three soils the severity levels induced by the strain CMM-1053 were similar to those observed in former studies. Most of the strains showed different behavior in relation to soils, except for CMM-1064 and CMM-1066. There was significant difference among disease severity levels and different inoculum densities. The three soils presented good stability in relation to the different R. solani strains, but the inoculum density may be a limiting factor in the implementation of the natural soil suppressiveness or the supressivity induction in conducive soils. / O caupi (Vigna unguiculata L.) é uma das culturas mais importantes da região Nordeste do Brasil, principalmente na economia de pequenos produtores rurais. A murcha-de-fusário e a rizoctoniose, causadas pelos fungos Fusarium oxysporum f.sp. tracheiphilum e Rhizoctonia solani, respectivamente, são as doenças mais freqüentes e de maior intensidade em caupi no Nordeste brasileiro. Esta tese teve como objetivos avaliar a supressividade natural de 66 solos do Nordeste brasileiro à murcha-de-fusário e rizotoniose do caupi, analisar as características físicas, químicas e biológicas dos solos associadas com a supressividade ou conducividade às doenças, bem como avaliar a estabilidade da supressividade de três solos à rizoctonose do caupi, considerando diferentes isolados e densidades de inóculo de R. solani. Em relação à severidade da murcha-de-fusário e da rizoctoniose do caupi, os solos avaliados foram agrupados desde fortemente supressivos a altamente conducivos. As principais variáveis envolvidas na supressividade da murcha-de-fusário foram elevados teores de fósforo e potássio, respiração basal (CO2 evoluído) e os índices de diversidade e eqüitabilidade microbiana. Para a rizoctoniose, foram determinadas correlações importantes com os níveis de fósforo, potássio e sódio, respiração basal e atividade enzimática de diacetato de fluoresceína. Não foram correlacionados fatores físicos com a supressividade à murcha-de-fusário, porém foi possível correlacionar os teores de areia, argila e silte com asupressividade e/ou conducividade da rizoctoniose. Três solos classificados como fortemente supressivos à rizoctoniose foram avaliados em relação a oito isolados e três densidades de inoculo de R. solani. Houve diferença significativa entre os solos e os isolados quanto aos níveis de severidade da doença. Nos três solos os níveis de severidade induzidos pelo isolado CMM-1053 foram similares aos verificados nos estudos prévios. A maioria dos isolados apresentou comportamentos diferente em função dos solos, com exceção dos isolados CMM-1064 e CMM-1066. Foi verificada diferença significativa entre os níveis de severidade da doença e as diferentes densidades de inoculo. Os três solos evidenciaram estabilidade em relação aos diferentes isolados de R. solani, porém a densidade de inóculo pode ser um fator limitante na implementação da supressividade natural dos solos ou da indução da supressividade em solos conducivos.

The soil-borne fungi Rhizoctonia solani Kuhn and Sclerotinia sclerotiorum De Bary are ubiquitous plant pathogens with a wide host range. They are among the most widespread and destructive diseases of many crops, including sunflowers. Although in many cases, the use of chemicals appears to be the most economical and efficient means of controlling plant pathogens, their environmental concerns and the development of tolerance in pathogen populations have led to drastic reduction in their usage and increased the need to find alternative means of disease control. The potential benefits of applying Trichoderma harzianum Rifai and silicon (Si) nutrition to plants have been extensively reviewed. In this study, the ability of T. harzianum (Eco-T®), soluble silicon, and their combination was evaluated on sunflower (Helianthus annuus L.), for their potential to suppress pathogenic strains of R. solani and S. sclerotiorum. The ability of this crop to take up and accumulate Si in different plant parts was also investigated. In vitro assessment of fungal responses to Si in PDA showed that both R. solani and S. sclerotiorum were inhibited in the presence of Si. More inhibition was observed as the Si concentration increased with a relative increase in pH. Maximum growth inhibition was observed at 3000 mg ;-1 – 6000 mg ;-1 of PDA. No difference in inhibition between the two pathogens was observed, thus confirming the fungitoxic/suppressive ability of high Si concentrations to fungal growth. In addition, in vivo trials showed that the Si concentration of 200 mg ;-1 applied weekly significantly increased the dry weight of plants inoculated with R. solani and S. sclerotiorum and was therefore considered the optimum concentration. Assessments on in vitro antifungal activities of Eco-T® on R. solani and S. sclerotiorum, showed that Eco-T® significantly inhibited mycelial growth, in both dual culture methods and volatile and non-volatile compounds produced by Eco-T®. In addition, the combination of Eco-T® and Si was most effective in suppressing damping-off and increasing plant dry weight of sunflower seedlings in the greenhouse. The combination of Si and Eco-T® significantly increased percentage germination, number of leaves and head dry weight of the sunflower cultivars tested. Silicon alone increased growth but was unable to control R. solani and S. sclerotiorum effectively. Rhizotron studies showed that S. sclerotiorum infected the host through the roots and the stem, whereas R. solani only infected the host through the roots. A study on Si uptake and distribution showed that sunflower accumulates Si in various plant tissues. Analysis of plant tissues revealed that more Si was accumulated in leaves > stems > roots, with the Si levels in leaves being significantly higher than in stems and roots. In conclusion, Si alone could be used to increase growth but was unable to control R. solani and S. sclerotiorum. However, Si together with Eco-T® provides an environmentally friendly alternative for the control of R. solani and S. sclerotiorum, and enhanced plant growth and yield. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.