The effects of Rhizoctonia solani on the hypocotyls of resistant and susceptible lines of lima bean were studied . The fungus attacks lima bean at one or more stages during host development and causes pre-and -postemergence damping-off, root rot, and foliage blight. The isolate of the fungus used in this study was obtained from infected radishes grown in Salt Lake County. Utah. The formation of infection cushions and modes of penetration by this fungus was no different on the resistant and susceptible lima bean hypocotyls . The infection process was studied under laboratory conditions . Differential staining showed that the fungal hyphae were closely appressed to the host surface , and at first along the longitudinal axis o f the epidermal cells. Later, hyphal branches grew in oblique and transverse directions . Aggregated hyphal tips formed infection cushions , which gave rise to one or more infection pegs that penetrated the host directly . Following penetration, both intercellular and intracellular hyphae were formed. The build-up of masses of hyphae occurred as club-shaped structures in the cortex of the susceptible lima bean hypocotyls , but were not observed in the resistant hypocotyls . The extents of infection in the resistant and susceptible lima bean hypocotyls were different at 7 days after inoculation. The hyphae in the susceptible hypocotyl had penetrated into vascular bundles and pith , whereas the hyphae had penetrated the cortex and pith of the resistant hypocotyl but were not observed in the vascular tissue. Stomatal penetration from individual hyphal side branches was rare and apparently of minor importance as a means of penetration by this isolate .

No description available.

Le complexe d'espèces Fusarium solani regroupe des champignons phytopathogènes également impliqués en pathologie humaine dans des infections parfois profondes et souvent de mauvais pronostic. Dans un premier temps, une méthode de MLST, s'appuyant sur 5 gènes de ménage a donc été développée. Validée sur 51 isolats épidémiologiquement distincts, cette méthode stable et reproductible présente un pouvoir discriminant de 99,1 %. Après comparaison à la technique de référence utilisée en phylogénie, un schéma consensus à 8 loci a été proposé. Dans un second temps, une étude de la sensibilité de ce pathogène à l'amphotéricine B et au voriconazole a été menée par deux techniques d'évaluation des CMI : microdilution CLSI M38-A2 et bandelettes E-test. Devant le paradoxe entre une sensibilité diminuée in vitro au voriconazole et la recommandation de cette molécule pour le traitement curatif de la fusariose humaine, des mécanismes de résistance ont été exploré. L'hypothèse d'un phénomène d'efflux n'a pas été retenue alors que celle d'une modification de la cible, la 14 alpha stérol déméthylase, peut être envisagée après la description de différentes mutations pour les isoformes CYP51A, B et C / Fusarium solani species complex includes phytopathogenic fungi also involved in human infections with poor prognosis. Firstly, MLST method, based on five housekeeping genes has been developed. This method has been validated on 51 isolates epidemiologically distinct, and has been shown to be stable and reproducible and provides a discriminating power of 99.1%. After comparison with the reference technique used in phylogeny, a consensus method with 8 loci has been proposed. Secondly, a study of the susceptibility to amphotericin B and voriconazole has been conducted with two MIC determination methods : CLSI M38-A2 microdilution and E-test. The paradox between decreased susceptibility to voriconazole in vitro and recommendation of this molecule for the curative treatment of Fusarium infections has lead to the exploration of resistance mechanisms. The hypothesis of an efflux phenomenon has not been retained whereas a change in the target, the sterol 14 alpha demethylase may be considered following the description of different mutations on proteins CYP51A, B and C

Made available in DSpace on 2017-07-10T17:37:25Z (GMT). No. of bitstreams: 1 Maria Isabel Balbi-Pena.pdf: 402140 bytes, checksum: 2e4a3baf75444b18009c52bff4d2c3f7 (MD5) Previous issue date: 2005-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Early blight, caused by Alternaria solani, is one of the most important diseases of tomato in Brazil. This disease affects leaves, stems, petioles and fruits causing important economicaI losses. New alternatives to fungicides have been evaluated to control the diseases with low environmental impact and low toxicity to living beings. The discovery of vegetal secondary compounds with antimicrobiotic activity or secondary compounds that induce disease resistance shows to be very promissory. Turmeric, Curcuma longa, has compounds in its rhizomes with proved antimicrobiotic activity. The objectives of this study were to evaluate the in vitro fungitoxic activity of turmeric extracts and curcumin against A. solani and to determinate their potential in the control of tomato early blight. Four different concentrations (1, 5, 10 and 20%) of aqueous extracts of turmeric rhizomes (sterilized by autoclavation) and four curcumin solutions (50, 100, 200 and 400 mg L-1) were incorporated into potato dextrose agar medium in order to evaluate fungal micelial growth and esporulation. To evaluate the effect of autoclavation, 10% and 15% turmeric extracts were sterilized by filtration. The effects of autoclavated and non autoclavated turmeric extracts and curcumin on in vitro spore germination were tested. The concentrations of 10 and 15% non autoclavated turmeric extracts inhibited the micelial growth by 38,2% and 23,2%, respectively, and the fungal sporulation by 71,7% and 87% respectively. When the turmeric extracts were autoclavated, neither micelial growth nor spore germination was inhibited and the effect on the sporulation was reduced, suggesting the presence of thermolabile antimicrobiotic compounds. The non autoclavated 5% extract inhibited by 15% the spore germination. At the highest concentration, the curcumin solution inhibited the micelial growth by 29,5%. Neither in vitro esporulation nor spore germination was affected by curcumin. At a greenhouse experiment, desease severity, fruit production and classification were evaluated. The treatments were: 1 and 10% turmeric extracts, 50 e 100 mg L-1 curcumin solutions, acibenzolar-S-metil (ASM) (2,5 g 100 L-1 of a.i.), copper oxychloride (110 g L-1 of a.i.), azoxystrobin (40 g L-1 of a.i.) and control (water). The disease control showed by turmeric extracts and curcumin solutions was similar to cuprous fungicide, but inferior to azoxystrobin control. There was no statistical difference in comercial fruit production between treatments. Only 50 mg L-1 curcumin treatment had higher porcentage of bigger fruits compared to the control. Another experiment with tomato plants growing in vases was performed with the subject of veryfing resistance induction. After 26 days of transplanting, the 7th. leaf was sprayed with turmeric extract (1 and 10%), curcumin (50 e 100 mg L-1), ASM (2,5 g a.i. 100 L-1) and water. Seventy two hours later, 7th. treated leaf and 8th. untreated leaf were inoculated with A. solani. At 7th. leaf, 10% turmeric extract and 100 mg L-1 curcumin treatments showed an statistically inferior area under disease progress curve, compared to the control, what could suggest induction of local resistance or direct antimicrobiotic activity. At 8th. leaf, only 10% turmeric extract shows significant difference compared with the control, what could mean a systemic resistance induced by turmeric extract. These results show the potential of turmeric and curcumin in the control in tomato early blight. / A pinta preta, causada por Alternaria solani, é uma das mais importantes doenças da cultura do tomateiro no Brasil. A doença ocorre em folhas, hastes, pecíolos e frutos, ocasionando elevados prejuízos econômicos. Várias alternativas aos fungicidas têm sido avaliadas nos últimos anos na busca de produtos que controlem satisfatoriamente as doenças, tenham pequeno impacto ambiental e baixa toxicidade aos seres vivos. A descoberta de muitos compostos secundários de plantas com atividade antimicrobiana e/ou indutores de resistência, mostra-se promissora. A cúrcuma, Curcuma longa, apresenta compostos em seus rizomas com comprovada atividade antimicrobiana. Dessa forma, os objetivos deste trabalho foram avaliar a atividade fungitóxica in vitro dos extratos brutos de cúrcuma e da curcumina contra A. solani e determinar o potencial dos mesmos no controle da pinta preta em tomateiro. Foram utilizados extratos brutos aquosos de rizomas de cúrcuma (esterilizados por autoclavagem) nas concentrações de 1, 5, 10 e 20% e curcumina nas concentrações de 50, 100, 200 e 400 mg L-1, os quais foram incorporados em meio de cultura batata-dextrose-ágar para avaliação de crescimento micelial e esporulação do fungo. Para avaliar o efeito da autoclavagem, foram testados extratos de cúrcuma a 10 e 15% esterilizados por filtração. Foi testado também o efeito dos extratos de cúrcuma autoclavados e não autoclavados e da curcumina na germinação de esporos in vitro. Os extratos de cúrcuma a 10 e 15% sem autoclavar, inibiram em 38,2% e 23,2% respectivamente o crescimento micelial e 71,7% e 87%, respectivamente, a esporulação do fungo. Quando autoclavados, não apresentaram inibição do crescimento micelial nem da germinação de esporos e a inibição da esporulação foi menor, indicando a presença de compostos antimicrobianos termolábeis. O extrato não autoclavado na concentração de 5%, inibiu um máximo de 15% a germinação dos esporos. A curcumina inibiu o crescimento micelial em 29,5% na maior concentração. Não foi verificado efeito da curcumina sobre a esporulação e a germinação de esporos in vitro. No ensaio in vivo, conduzido em casa de vegetação, foi avaliada a severidade da doença e a produção e classificação de frutos. Os tratamentos utilizados foram: extrato de cúrcuma (1 e 10%), curcumina (50 e 100 mg L-1), acibenzolar-S-metil (ASM) (2,5 g 100 L-1 de i.a.), oxicloreto de cobre (110 g L-1 de i.a.), azoxystrobin (40 g L-1 de i.a.) e testemunha (água). A curcumina e os extratos brutos de cúrcuma apresentaram níveis de controle de pinta preta, no campo, similares ao tratamento com fungicida cúprico, mas inferior ao azoxystrobin. Não houve diferenças estatísticas na produção comercial de frutos entre tratamentos. Somente o tratamento de curcumina 50 mg L-1 apresentou maior porcentagem de frutos grandes em relação à testemunha. Outro ensaio foi conduzido com o objetivo de verificar a indução de resistência em plantas cultivadas em vasos. Aos 26 dias após o transplante, a 7ª folha da planta recebeu extrato de cúrcuma (1 e 10%), curcumina (50 e 100 mg L-1), ASM (2,5 g 100 L-1 de i.a.) ou água, por aspersão. Após 72 h, a 7a folha tratada e a 8a folha (não tratada) foram inoculadas com A. solani. Na 7ª folha, os tratamentos com extrato de cúrcuma 10% e curcumina 100 mg L-1 apresentaram um valor de área abaixo da curva de progresso da doença estatisticamente menor à testemunha, o que poderia indicar indução de resistência local ou atividade antimicrobiana direta. Na 8ª folha, somente o extrato de cúrcuma 10% apresentou diferença significativa com a testemunha o que poderia indicar uma indução de resistência sistêmica pelo extrato bruto de cúrcuma. Esses resultados indicam o potencial de cúrcuma e curcumina para o controle de pinta preta no tomateiro.

O Brasil tem uma posição de destaque mundial na produção de frutas e alguns grãos, os quais são comercializados in natura ou na forma de produtos processados. O processamento têm várias vantagens, porém gera grandes quantidades de resíduos, os quais têm sido aproveitados para a alimentação animal e geração de energia. Entretanto, muito tem sido relatado sobre o potencial bioativo desses materiais, dentre eles a ação fungitóxica de alguns de seus compostos sobre fungos fitopatogênicos. Assim, o objetivo desse trabalho foi avaliar o potencial de extratos de resíduos agroindustriais de abacate, uva, café, manga, abacaxi, maracujá e caju na inibição do crescimento micelial in vitro dos fungos Fusarium pallidoroseum, Colletotrichum dematium, Rhizoctonia solani e Phomopsis sp., bem como a composição química do resíduo mais promissor. Os resíduos foram liofilizados, moídos e submetidos a extração com etanol 80% (etanol:água; 8:2, v/v) em banho de ultrassom (extrato denominado bruto ou EB). O EB também foi tratado com a resina Amberlite XAD-2, visando à eliminação de açúcares e interferentes, dando assim origem ao extrato semi-purificado (EP). Os extratos que apresentaram alto rendimento foram avaliados quanto à atividade antifúngica in vitro e teor de compostos fenólicos totais. A amostra que apresentou os melhores índices de inibição foi selecionada para dar continuidade ao estudo, sendo a mesma fracionada em coluna de gel Sephadex LH-20. Os extratos e as frações ativas, detectadas pelo ensaio de bioautografia, foram analisadas quanto a composição química pelas técnicas de HPLC e GC/MS. Na análise de fenólicos totais os maiores teores encontrados foram para a casca de abacate, enquanto que para o ensaio de inibição de crescimento micelial in vitro o melhor resultado foi para a semente de abacate, tanto para o EB quanto para o EP. Desta maneira, a semente de abacate foi selecionada para as etapas posteriores. Para o fracionamento em gel Sephadex LH-20 foi eleito o EP para F. pallidoroseum enquanto que para os demais fungos foi eleito o EB. No fracionamento do EP obtiveram-se 13 frações, sendo que as frações 3 e 4 foram ativas, enquanto que no do EB obtiveram-se nove, sendo as frações 3, 4 e 5 ativas. Pela técnica de HPLC foram detectados em comum nas frações 3, 4 e 5 do EB dois compostos majoritários, e nas frações 3 e 4 do EP, sete compostos, os quais não puderam ser identificados pelos padrões comerciais disponíveis. Já pela técnica de GC/MS foi possível a identificação de quatro compostos em comum nas frações ativas do EB e de 11 nas frações do EP. Dentre os compostos presentes nas frações ativas, foram identificados ácidos graxos, os quais têm sido reconhecidos por apresentarem ação antifúngica. Assim, pode-se concluir que os resíduos agroindustriais estudados são fontes de compostos com atividade antifúngica, podendo assim ser uma alternativa para o controle de fungos fitopatogênicos à cultura da soja / Brazil holds an important position in the world production of fruit and some grains, which are commercialized in natura or in processed products. The processing has several advantages, but generates large amounts of by-products which have been used for animal feed and power generation. However, bioactive potential of these materials have been reported, including the fungitoxic effect. The goal of this study was to evaluate the potential of agro-industrial by-products extracts of avocado, grape, coffee, mango, pineapple, passion fruit and cashew to inhibit in vitro mycelial growth of fungi Fusarium pallidoroseum, Colletotrichum dematium, Rhizoctonia solani and Phomopsis sp. as well as the chemical composition of the most promising by-products. The by-products were freeze-dried, milled and the extraction was done with ethanol 80% (ethanol:water, 8:2, v/v) in an ultrasound bath (called crude extract or CE). The CE was also treated with Amberlite XAD-2 to eliminate sugars and interfering compounds so that the semi-purified extract (PE) could be obtained. Extracts with high yield were evaluated to in vitro antifungal activity and phenolic compounds content. Samples with the best inhibition rates were selected to continue this study, and it was fractioned on gel Sephadex LH-20. The extracts and the active fractions, detected by bioautography, were analyzed by HPLC and GC/MS. The highest phenolic content was found in the avocado peel, meanwhile for the mycelial growth inhibition in vitro, the best result was found in the avocado seeds for both extracts (CE and PE). Thus, avocado seed was selected for subsequent steps. For fractionation on Sephadex LH-20 gel, PE was chosen for F. pallidoroseum and CE for the other fungi. For PE, 13 fractions were obtained in which fractions 3 and 4 were active. For CE, 9 fractions were obtained and the actives were 3, 4 and 5. In CE, HPLC technique detected two major compounds in common in fractions 3, 4 and 5. In PE, seven major compounds were detected in fractions 3 and 4, which could not be identified by commercial available standards. By the GC/MS technique was possible to identify four compounds in common in the active CE fractions and 11 in PE. Among the compounds presented in the active fractions, fatty acids were identified. It has been reported that antifungal action has been found in these compounds. Therefore, the studied agroindustrial by-products are sources of compounds with antifungal activity and they can be used as an alternative to control phytopathogenic fungi on soybean

O Brasil tem uma posição de destaque mundial na produção de frutas e alguns grãos, os quais são comercializados in natura ou na forma de produtos processados. O processamento têm várias vantagens, porém gera grandes quantidades de resíduos, os quais têm sido aproveitados para a alimentação animal e geração de energia. Entretanto, muito tem sido relatado sobre o potencial bioativo desses materiais, dentre eles a ação fungitóxica de alguns de seus compostos sobre fungos fitopatogênicos. Assim, o objetivo desse trabalho foi avaliar o potencial de extratos de resíduos agroindustriais de abacate, uva, café, manga, abacaxi, maracujá e caju na inibição do crescimento micelial in vitro dos fungos Fusarium pallidoroseum, Colletotrichum dematium, Rhizoctonia solani e Phomopsis sp., bem como a composição química do resíduo mais promissor. Os resíduos foram liofilizados, moídos e submetidos a extração com etanol 80% (etanol:água; 8:2, v/v) em banho de ultrassom (extrato denominado bruto ou EB). O EB também foi tratado com a resina Amberlite XAD-2, visando à eliminação de açúcares e interferentes, dando assim origem ao extrato semi-purificado (EP). Os extratos que apresentaram alto rendimento foram avaliados quanto à atividade antifúngica in vitro e teor de compostos fenólicos totais. A amostra que apresentou os melhores índices de inibição foi selecionada para dar continuidade ao estudo, sendo a mesma fracionada em coluna de gel Sephadex LH-20. Os extratos e as frações ativas, detectadas pelo ensaio de bioautografia, foram analisadas quanto a composição química pelas técnicas de HPLC e GC/MS. Na análise de fenólicos totais os maiores teores encontrados foram para a casca de abacate, enquanto que para o ensaio de inibição de crescimento micelial in vitro o melhor resultado foi para a semente de abacate, tanto para o EB quanto para o EP. Desta maneira, a semente de abacate foi selecionada para as etapas posteriores. Para o fracionamento em gel Sephadex LH-20 foi eleito o EP para F. pallidoroseum enquanto que para os demais fungos foi eleito o EB. No fracionamento do EP obtiveram-se 13 frações, sendo que as frações 3 e 4 foram ativas, enquanto que no do EB obtiveram-se nove, sendo as frações 3, 4 e 5 ativas. Pela técnica de HPLC foram detectados em comum nas frações 3, 4 e 5 do EB dois compostos majoritários, e nas frações 3 e 4 do EP, sete compostos, os quais não puderam ser identificados pelos padrões comerciais disponíveis. Já pela técnica de GC/MS foi possível a identificação de quatro compostos em comum nas frações ativas do EB e de 11 nas frações do EP. Dentre os compostos presentes nas frações ativas, foram identificados ácidos graxos, os quais têm sido reconhecidos por apresentarem ação antifúngica. Assim, pode-se concluir que os resíduos agroindustriais estudados são fontes de compostos com atividade antifúngica, podendo assim ser uma alternativa para o controle de fungos fitopatogênicos à cultura da soja / Brazil holds an important position in the world production of fruit and some grains, which are commercialized in natura or in processed products. The processing has several advantages, but generates large amounts of by-products which have been used for animal feed and power generation. However, bioactive potential of these materials have been reported, including the fungitoxic effect. The goal of this study was to evaluate the potential of agro-industrial by-products extracts of avocado, grape, coffee, mango, pineapple, passion fruit and cashew to inhibit in vitro mycelial growth of fungi Fusarium pallidoroseum, Colletotrichum dematium, Rhizoctonia solani and Phomopsis sp. as well as the chemical composition of the most promising by-products. The by-products were freeze-dried, milled and the extraction was done with ethanol 80% (ethanol:water, 8:2, v/v) in an ultrasound bath (called crude extract or CE). The CE was also treated with Amberlite XAD-2 to eliminate sugars and interfering compounds so that the semi-purified extract (PE) could be obtained. Extracts with high yield were evaluated to in vitro antifungal activity and phenolic compounds content. Samples with the best inhibition rates were selected to continue this study, and it was fractioned on gel Sephadex LH-20. The extracts and the active fractions, detected by bioautography, were analyzed by HPLC and GC/MS. The highest phenolic content was found in the avocado peel, meanwhile for the mycelial growth inhibition in vitro, the best result was found in the avocado seeds for both extracts (CE and PE). Thus, avocado seed was selected for subsequent steps. For fractionation on Sephadex LH-20 gel, PE was chosen for F. pallidoroseum and CE for the other fungi. For PE, 13 fractions were obtained in which fractions 3 and 4 were active. For CE, 9 fractions were obtained and the actives were 3, 4 and 5. In CE, HPLC technique detected two major compounds in common in fractions 3, 4 and 5. In PE, seven major compounds were detected in fractions 3 and 4, which could not be identified by commercial available standards. By the GC/MS technique was possible to identify four compounds in common in the active CE fractions and 11 in PE. Among the compounds presented in the active fractions, fatty acids were identified. It has been reported that antifungal action has been found in these compounds. Therefore, the studied agroindustrial by-products are sources of compounds with antifungal activity and they can be used as an alternative to control phytopathogenic fungi on soybean

Cette étude a évalué in vitro l'effet de différents éléments minéraux sur la croissance et le développement de Helminthosporium solani, agent responsable de la gale argentée de la pomme de terre. Les résultats obtenus ont démontré que la source et la concentration d'éléments minéraux étudiés avaient une influence sur la croissance mycélienne et la production de conidies chez ce champignon. L'augmentation des concentrations d'azote et de calcium dans le milieu de culture a généralement diminué la croissance mycélienne mais stimulé la production de conidies viables, tandis que l'augmentation des concentrations de phosphore et de potassium a eu l'effet contraire. À la lumière des résultats obtenus, il apparaît évident que ces travaux pourraient trouver des applications dans la mise au point de milieux de culture favorables au développement de H. solani. Ils pourraient également présenter un intérêt pour l'élaboration de substrats répressifs envers la gale argentée de la pomme de terre.

La dissipation des Hydrocarbures Aromatiques Polycycliques (HAP), polluants persistants majoritaires des sols de friches industrielles, implique l'action de microorganismes bactériens et fongiques. Cependant, leur contribution relative à la dissipation in situ, en fonction des interactions entre ces microorganismes ou avec les plantes et les polluants, est mal connue et les communautés fongiques ont été très peu étudiées dans de tels environnements. L'objectif de cette thèse était de préciser l'écodynamique des HAP dans la rhizosphère sous l'effet des microorganismes et de leurs interactions et d'évaluer la diversité fongique dans des sols contaminés. La dynamique des communautés fongiques a été étudiée in situ pendant 5 années, par PCR en temps réel et Temporal Temperature Gradient Electrophoresis (TTGE), dans un sol historiquement contaminé en présence ou non de plantes et dans le même sol ayant subi un traitement de remédiation par désorption thermique. Les plantes avaient un effet positif sur l'abondance et la diversité des champignons et étaient le facteur déterminant la structure des communautés fongiques, dominées par les Ascomycètes. D'autre part, des souches bactériennes et fongiques ont été isolées de ce sol et testées pour leur capacité à dégrader les HAP in vitro. Parmi celles-ci, la bactérie Arthrobacter oxydans Pyr2MsHM11 et le champignon Fusarium solani MM1 ont été choisies comme souches modèles pour étudier leur action individuelle ou conjointe sur la dissipation de trois HAP, dans différentes conditions, des plus simples (cultures liquides) aux plus complexes (microcosmes de sol planté en présence d'une microflore). Les résultats ont montré l'importance fondamentale des interactions entre microorganismes, notamment des phénomènes de compétition, pour la croissance des souches modèles et pour l'expression de leurs potentiels de dissipation des HAP / The dissipation of Polycyclic Aromatic Hydrocarbons (PAHs), very common and persistant pollutants in soils from industrial wastelands, involve the action of bacterial and fungal microorganisms. However their respective contribution, and the influence of the microbial and plant-microbe interactions on in situ PAH dissipation, are poorly known and fungal communities were scarcely studied in such environments. This work aimed to study the fate of PAHs in rhizosphere under the influence of microorganisms and their interactions and to estimate the fungal diversity in contaminated soils. The dynamic of fungal communities was monitored in situ for 5 years, by real-time PCR and Temporal Temperature Gradient Electrophoresis (TTGE) in an aged PAH-polluted soil and in the same soil treated by thermal desorption. The results showed that plants had a positive effect on fungal abundance and diversity and were the main driver of fungal community structure, dominated by Ascomycetes. Besides, bacterial and fungal strains were isolated from this soil and screened for their ability to dissipate PAHs in vitro. Among them, the bacteria Arthrobacter oxydans Pyr2MsHM11 and the fungus Fusarium solani MM1 were chosen as model strains to study their individual and simultaneous effect on PAH dissipation in different experimental conditions, from liquid cultures to planted soil microcosms with a complex microflora. It was found that interactions between microorganisms, notably competition, had a crucial influence on their growth and on the expression of their PAH dissipation potential

Die Kartoffel, eines der wichtigsten Nahrungsmittel weltweit, wird unter anderem von dem Erreger Rhizoctonia solani Kühn befallen. Durch dieses Pathogen hervorgerufene Qualitäts- und Ertragsverminderungen können zu erheblichen ökonomischen Verlusten führen. Da derzeitig verfügbare Bekämpfungsmaßnahmen nur eine eingeschränkte Effektivität aufzeigen, sind alternative Bekämpfungsstrategien dringend notwendig. Der Einsatz resistenter Sorten stellt eine effektive, umweltfreundliche Alternative dar, jedoch ist derzeit nur wenig über die der Resistenz der Kartoffel gegenüber R. solani zugrundeliegenden Mechanismen bekannt. Ziel dieser Arbeit war es, Merkmale aufzufinden, die mit einer erhöhten Feldresistenz der Kartoffel gegenüber R. solani korrelieren und zukünftig als Marker in der Züchtung zur Einschätzung des Resistenzgrads von Sorten genutzt werden können. Auf der Grundlage von Feldversuchen wurden zwei Kartoffelgenotypen mit einem unterschiedlichen Grad der Feldresistenz gegenüber R. solani für vergleichende molekularbiologische und biochemische Analysen ausgewählt. Die Analyse des Expressionsniveaus ausgewählter Abwehrgene zeigte, dass die Kartoffelsorte mit geringerer Anfälligkeit ein konstitutiv höheres Expressionsniveau aufweist als die Sorte mit einer höheren Anfälligkeit. Im Gegensatz zur stärker anfälligen Sorte wurde in Wurzeln und Stängeln der weniger anfälligen Sorte kein erhöhtes Expressionsniveau der Abwehrgene infolge der Infektion mit R. solani festgestellt. Zudem wies die weniger anfällige Sorte höhere Gehalte an α-Chaconin and α-Solanin sowie Nicotiflorin auf. Anhand von in vitro Untersuchungen wurde ein wachstumshemmender Effekt dieser Komponenten auf R. solani festgestellt. Weiterhin wurde ein geringerer Gehalt an R. solani-DNA in den Wurzeln der weniger anfälligen Sorte determiniert. Demnach scheint eine geringere Anfälligkeit der Kartoffel gegenüber diesem Erreger mit einer höheren, präformierten pflanzlichen Immunabwehr korreliert zu sein. / Potato, the fourth most important food crop worldwide, is also target of many pests and microbial pathogens including the fungus Rhizoctonia solani Kühn. The infection of potato with this pathogen leads to considerable economic losses. The soil-borne nature, the formation of melanised sclerotia, and the limited efficacy of fungicides impair the control of this pathogen and strengthen the necessity for alternative control measures. A very effective alternative is the use of resistant cultivars. Quantitative differences in the degree of resistance of potato to R. solani have been repeatedly observed in the field. However, until now there is no information available regarding the underlying mechanisms contributing to the resistance level. This thesis aimed at revealing mechanisms in potato which contribute to the manifestation of a certain degree of field resistance to R. solani. Based on the screening of various potato genotypes in field trials, two potato cultivars distinctly differing in the level of resistance to R. solani were selected for further molecular and biochemical analyses. The cultivar with a higher degree of resistance showed higher constitutive expression of defence-related genes. In contrast to the less resistant cultivar, no distinct increase of the defence-gene expression level was detectable upon pathogen infection in this cultivar. Moreover, contents of the glycoalkaloids α-chaconine and α-solanine and of the flavonol nicotiflorin were higher compared to the less resistant cultivar. Using in vitro culture tests, a growth-reducing effect of these compounds on R. solani was confirmed. Concluding, a higher resistance of potato cultivars to R. solani seems to be related to a higher expression level of defence-related genes and to a higher content of plant secondary metabolites. This enhanced constitutive defence level resulted in a lower pathogen colonisation of the plant, thus contributing to a reduced disease severity in the field.

Fusarium é um grande gênero de fungos filamentosos amplamente distribuídos que são importantes patógenos de plantas, animais e humanos. As doenças causadas por Fusarium spp. geram grandes perdas econômicas na produção de frutas, legumes, cereais e de celulose. Em humanos, o controle da fusariose com apenas um antifúngico é ineficaz, apresentando uma elevada taxa de mortalidade, especialmente em pacientes imunocomprometidos. A maior resistência aos fungicidas utilizados atualmente tem estimulado o desenvolvimento de novas tecnologias mais eficazes para o controle de fungos patogênicos. Assim, é necessária a busca de alternativas para o controle de microrganismos em ambas as áreas, clínica e agrícola. A inativação fotodinâmica antimicrobiano (IFA) é uma promissora plataforma antifúngica alternativa que pode ser utilizada para controlar o inóculo de fungos em mamíferos e no meio ambiente. A IFA baseia-se na utilização de um fotossensibilizador (FS) que se acumula na célula fúngica alvo. A exposição do FS à luz com um comprimento de onda apropriado, inicia um processo fotoquímico que produz espécies reativas de oxigênio (EROs), principalmente o oxigênio singleto, causando um dano oxidativo não especifico levando a morte da célula fúngica, sem dano significativo às células do hospedeiro. Em comparação com os fungicidas utilizados atualmente, a multiplicidade dos danos causados pelas EROs, reduzem a chance de selecionar microrganismos tolerantes. No presente trabalho, avaliamos o efeito da IFA com a combinação de luz vermelhas com fluências de 10 e 15 J cm-2 e cinco FS fenotiazínicos, azul de metileno (MB), azul de toluidina O (TBO), novo azul de metileno N fórmula sem zinco (NMBN), novo azul de metileno N formula com zinco (NMBN Zn) e um novo fenotiazínico pentacíclico S137, em microconídios não germinados e 4 h-germinados de Fusarium oxysporum, F. moniliforme e F. solani. A IFA com NMBN Zn resultou em uma redução de aproximadamente 5-logs na sobrevivência dos microconídios não germinados (quiescentes) e 4 h-germinados (metabolicamente ativos) das três espécies de Fusarium quando expostas a luz na fluência de 15 J cm-2. A lavagem dos microconídios não germinados e 4 h-germinados para retirar o excesso de FS antes da exposição à luz reduziu, porém não impediu a morte provocada pela IFA. A IFA com todos os FS e fluência aumentou a permeabilidade da membrana celular dos microconídios nas três espécies de Fusarium. O dano oxidativo causado pelas EROs produzidos durante o processo fotoquímico da IFA foi avaliado nos lipídios, proteínas e DNA dos microconídios das espécies de Fusarium. Foi observado um aumento da peroxidação lipídica em microconídios das três espécies de Fusarium após a IFA com NMBN Zn e S137. Observamos o aumento na carbonilação de proteínas em microconídios de F. oxysporum após IFA subletal com todos os FS. O aumento no dano do DNA em microconídios não germinados e 4 h-germinados foi observado apenas para o S137 na fluência de 0, 10 e 15 J cm-2. Nossos estudos expandem a compreensão da inativação fotodinâmica de fungos filamentosos / Fusarium is a large genus of filamentous fungi widely distributed wich are important pathogens of plants, animals and humans. Crop diseases caused by Fusarium generate great economic losses in the production of fruit, vegetables, cereals, and cellulose. In humans the control of progression of fusariosis by single-agent antifungal therapy is problematic, leading to a high mortality rate, especially with immunocompromised patients. The increased tolerance to currently used fungicides has stimulated the development of novel and effective technologies to control pathogenic fungi. Thus, the search for alternatives to control microorganisms is necessary in both, clinical and agricultural areas. Antimicrobial photodynamic treatment (APDT) is a promising alternative antifungal platform that can be used to control fungi both in mammalian hosts and in the environment. APDT is based on the use of a photosensitizer (PS) that accumulates in the target fungal cell. The exposure of the PS to light of an appropriate wavelength starts a photochemical process that produces reactive oxygen species (ROS), especially singlet oxygen, leading to non-specific oxidative damage causing the death of the fungal cell without significant harm to the host cells. In comparison with currently used fungicides, the multiple and variable targets of ROS reduce the chance of selecting tolerant microorganisms. In the present study, we evaluated the effect of APDT with the combination of red light with fluence of 10 and 15 J cm-2, and five phenotiazinium photosensitizer, methylene blue (MB), toluidine blue O (TBO), new methylene blue N zinc free form (NMBN), new methylene blue N zinc chloride double salt (NMBN Zn) and a novel pentacyclic phenothiazinium S137, on ungerminated and germinated microconidia of Fusarium oxysporum, F. moniliforme and F. solani. APDT with NMBN Zn resulted in a reduction of approximately 5 logs in the survival of the quiescent ungerminated microconidia and metabolically active germinated microconidia of the three Fusarium species when the light fluence of 15 J cm-2 was applied. Washing out the PS from both ungerminated and germinated microconidia before light exposure reduced but did not prevent the killing effect of APDT. APDT with all the PS and fluences increased cell membrane permeability for the three Fusarium species. The oxidative damage caused by ROS produced during the photochemical process of APDT, was evaluated in the lipids, proteins and DNA present in the microconidia. Increases in lipid peroxidation in microconidia of the three Fusarium species were observed only after APDT with NMBN Zn and S137. Proteins oxidative damage was observed by the increase in protein carbonylation in microconidia of the F. oxysporum after APDT with all PS. The increases in DNA damage from both ungerminated and germinated microconidia was observed only for S137 at fluence of 0, 10 and 15 J cm-2. Our study expands the understanding of photodynamic inactivation in filamentous fungi