Rhizoctonia solani (AG-3), the causal agent of Rhizoctonia disease of potato, overwinters as sclerotia on potato tubers. To develop a biocontrol strategy based on the prevention of the sclerotial germination, an isolation of microorganisms colonizing sclerotia of infected potato tubers (cultivars Norland, Atlantic and Souris), was conducted. In vitro screening was used to select effective antagonistic fungi against Rhizoctonia solani. Fifty fungal isolates were selected in order to cover all identified genera and potato variety and examined for their ability to inhibit germination of sclerotia which were incubated with the test fungus for 14 days. Twenty-four (24) fungal isolates were retained based on their ability to reduce sclerotial viability by more than 50% as compared with 100% viability of untreated sclerotia. These 24 isolates were further examined for their ability to protect Table beet seedlings against the pathogen in greenhouse soils. Based on their ability to protect Table beet seedlings from Rhizoctonia infections and to increase the number of secondary roots and root length isolates, F2, F11, F132, F158, and F258 were screened and test their efficacy to increase beet seed germination in field soils. (Abstract shortened by UMI.)

Tobacco phylloplanins (T-phylloplanin) are a group of closely-related glycoproteins that are formed and disposed at the interface between the plant aerial surface (the phylloplane) and the atmosphere. They are synthesized in short procumbent trichomes and are secreted to aerial surfaces where they are thought to serve the plant as a first line of defense against fungal pathogens. Here it is shown using in vitro and in planta assays that tobacco and sunflower phylloplanins have broad-spectrum antifungal activities against spores - and also hyphae for two species - of several true fungi. Field tests show that T-phylloplanin reduces diseases caused by three important fungal pathogens of turf grasses. Tobacco phylloplanins are distinct proteins but they have properties in common with small, membrane-pore-forming, antimicrobial peptides formed by other organisms. To directly determine if T-phylloplanin has pore-forming activity we monitored conductivity change and specific ion leakage from spores and hyphae in suspension. Results indicate that phylloplanin causes fungal membrane disruption that leads to ion depletion and cell death. Having observed broad efficacy of T-phylloplanin against spores and/or hyphae of several true fungi, but no activity towards hyphae of the oomycetes, Pythium and Peronospora parasitica, we tested for possible effects on zoospores of the latter two pathogens. T-phylloplanin was shown to be effective against their zoospores, extending the efficacy of T-phylloplanin to include water molds. In the course of these experiments we also tested the effects of the diterpene cis-abienol that is secreted from tall trichomes of tobaccos and found this compound impacted zoospores and could prevent black shank disease caused by P. parasitica when applied to soil-grown tobaccos as a root drench. Thus, results of these studies with phylloplanins and cis-abienol, two different tobacco surface accumulated compounds are consistent with their serving the plant as first line of defense systems against a wide array of invading fungal pathogens. Phylloplanins and cis-abienol may be useful for controlling fungal diseases in tobacco float beds. The efficacy shown here for T-phylloplanin control of fungal pathogens of turf grasses in the field suggests that this natural product may find use in IPM of turf and other crops.

Kentucky reported a solid 13.1% growth in certified organic land from 1997 to 2002. The relative lack of research on disease management practices in Kentucky consistent with organic regulations is an issue that needs to be addressed to provide more reliable information to local farmers. Thus, the first objective of this research was to investigate the potential disease control obtained with natural, organically certifiable spray materials against Colletotrichum orbiculare in vitro and in vivo. The second objective was to test certifiable spray materials in combinations to identify synergistic interactions. The third objective was to evaluate Organic Material Review Institute (OMRI)-certified materials for managing Septoria leaf spot and early blight in tomato under field conditions. The fourth objective was to evaluate chitosan-based products against C. orbiculare in vitro and in vivo. Essential oils, Trilogy®, and Actinovate®, failed to suppress C. orbiculare in vitro as well as cucurbit anthracnose. Bicarbonate salts, Regalia®SC, Sonata®, copper based-products, lime sulfur and water-soluble chitosan showed high antifungal activity in vitro. Bicarbonate salts, Sonata®, Serenade Max®, Soil Gard 12G®, copper based-products and lime sulfur reduced anthracnose disease severity in vivo. In the synergism experiments only a limited number of mixtures showed synergistic interactions, but even in those cases, the effect was not consistent between experiments. The main response obtained was antagonism. In field experiments the most effective fungicides for managing Septoria leaf spot and early blight of tomato were copper-based fungicides. None of the biological-based products (Sonata® and Serenade Max®)), plant-based extracts (Trilogy® and Regalia® SC), chitosan, ammonium bicarbonate nor horticultural lime sulfur provided a significant reduction in disease severity. For the fourth objective, water-soluble chitosan with a molecular weight between 3 to 10 kDa (80 and 85% deacetylated) showed the highest antifungal activity among all chitosan-based products evaluated in vitro. Also, combining the in vitro and in vivo results suggest that the antifungal activity of chitosan-based products is molecular weight- and concentration-dependent. These results provide a significant advance in the evaluation of the efficacy of OMRI-certified materials and natural materials to help organic farmers in Kentucky and the USA to manage diseases.

La qualité de présentation d'une pomme de terre de consommation, Solanum tuberosum L., commercialisée en produit frais est devenue une exigence et un enjeu économique significatif dans les relations commerciales. Compte tenu du mode de reproduction par voie végétative de cette espèce, ces exigences sont également imposées au tubercule de semence. Organe de réserve et de propagation, le tubercule est produit sous terre, ce qui l'expose aux microorganismes telluriques et le rend potentiellement porteur d'altérations superficielles dont l'origine n'est pas encore clairement identifiée pour certaines d'entre elles. L'objectif de ce travail est de recenser et de caractériser ces altérations superficielles du tubercule et d'en déterminer les causes. Après l'établissement d'une nomenclature et d'une classification consensuelles des défauts observables sur tubercule, deux hypothèses ont été formulées et testées: (1) les défauts sont d'origine pathogène et/ou (2) ils résultent d'une réponse de la plante à des stress environnementaux. L'évaluation de la première hypothèse a mené à l'identification d'une grande diversité de microorganismes vivant à la surface des tubercules altérés. Leur pouvoir pathogène a été testé par une série de tests biologiques. Ceux-ci ont permis de reproduire les défauts sur des tubercules néoformés et de vérifier les postulats de Koch pour le champignon Rhizoctonia solani responsable de la formation de sclérotes. Pour bon nombre d'autres défauts visuels, aucune relation claire entre un microorganisme et une altération n'a pu être établie. Une étude de la structure des communautés microbiennes de la géocaulosphère de tubercules, altérés ou non, a démontré que les communautés fongiques et bactériennes se comportaient selon des dynamiques différentes au cours de la culture et en fonction de l'état sanitaire du tubercule de semence mais aucune relation de causalité n'a pu être mise en évidence. Il a par contre été noté une augmentation de la population de R. solani autour des tubercules altérés. La diversité des isolats d'origine française et européenne associés aux altérations des tubercules a donc été caractérisée. Elle révèle l'existence de relations phylogénétiques indépendantes de l'origine géographique et du cultivar hôte et suggère l'existence de d'événements génétiques fréquents et d'un brassage génétique entre les populations de R. solani. Le test de la seconde hypothèse a consisté à rechercher une implication potentielle de différents facteurs abiotiques dans la formation des altérations superficielles. L'analyse d'une enquête menée auprès d'agriculteurs a mis en évidence l'implication du pH, de certaines pratiques culturales, de la sensibilité de cultivars et de conditions météorologiques particulières dans l'occurrence de certains défauts. Ce travail a permis de clarifier la nomenclature des altérations, de confirmer l'implication de R. solani dans l'apparition de certaines d'entre elles et d'envisager de nouvelles hypothèses quant à la formation de défauts suite à une réponse de la plante à un stress environnemental. Ainsi, une voie a été ouverte vers la résolution de la problématique posée par toute une filière professionnelle, responsable de la mise en marché d'un produit frais de grande consommation, et répondant aux exigences du marché en matière de présentation, qualité culinaire et, mode de production respectueux de l'environnement.

A time course study was conducted to monitor disease development and expression of the defense-related genes phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and hydroxyproline-rich glycoprotein (HRGP) in bean (Phaseolus vulgaris L.) plants colonized by the arbuscular mycorrhizal (AM) fungus Glomus intraradices , and post-infected with the soil-borne pathogen Rhizoctonia solani. Pre-colonization of bean plants by the AM fungus did not significantly reduce the severity of rot symptoms. RNA blot analysis revealed a systemic increase in transcript levels of the four defense-related genes in response to R. solani infection. On the other hand, pre-colonization of bean plants with G. intraradices elicited no change in PAL, CHS and CHI transcripts, but an increase of HRGP transcripts in leaves was detected. A differential and systemic alteration in the expression of all four defense genes was observed in AM beans post-infected with R. solani. Depending on the time after infection with R. solani and the tissue examined, varying responses from stimulation, suppression, to no change in transcript levels were detected.

The effect of the arbuscular mycorrhizal symbiosis at reducing the incidence of root diseases has received considerable attention. However, information on the role of mycorrhizae in reducing disease incidence of Fusarium root rot of beans (Phaseolus vulgaris), caused by the root pathogen Fusarium solani f. sp. phaseoli, is scarce. A study was undertaken to investigate how the arbuscular mycorrhizal fungus (AMF) Glomus intraradices affects disease development and population number of F. solani f. sp. phaseoli in the mycorhizosphere of bean plants growing in an experimental microcosm unit. This newly designed unit facilitated the spatial monitoring and quantification of both the symbiont and pathogen in different ecological soil regions of the mycorrhizosphere using compartmentation based on a physical segregation of roots, colonized or not by AMF (rhizosphere), AMF mycelium alone (mycosphere), or none (bulk soil). To study the interaction between both organisms, the experimental set-up consisted of a randomized complete block design using bean seedlings pre-colonized or not for 28 days by G. intraradices and infected or not for 6 days with F. solani f. sp. phaseoli. Monitoring of population number of the symbiont and the pathogen in bean plants and in the different mycorrhizosphere soil compartments was achieved with quantitative real-time PCR using specific molecular probes for each fungus, and with cultivation-dependant or morphological based methods. The results of this study indicated that non-mycorrhizal bean plants infected with the pathogen had typical root rot symptoms while infected plants that were pre-colonized by G. intraradices remained free of disease. The population number of F. solani f. sp. phaseoli was significantly reduced in the root system and in each of the mycorrhizosphere soil compartments of mycorrhizal infected plants. The mycorrhizosphere population of G. intraradices was not significantly modified, although the p

Three pages of addenda pasted inside back cover. / Bibliography: leaves 166-189. / xii, 189, [12] leaves, [24] leaves of plates : ill. (some col.), map ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Rhizoctonia solani is a complex species comprising morphologically basidiomycetous imperfect fungi. This study aimed to determine genetic diversity within R. solani AG-3 causing rhizoctonia disease of potato in South Australia. For this purpose, pectic zymogram, PCR, DNA fingerprinting and RFLP techniques were used in conjunction with traditional plant pathology procedures. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1996?

Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 66-73. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Resumo: 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. / Abstract: 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. / Orientadora: Rita de Cássia Panizzi / Coorientador: Nelson Moreira de Carvalho / Banca: Margarete Camargo / Banca: Adriana Zanin Kronka / Mestre

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-04-20T13:00:17Z No. of bitstreams: 1 texto completo.pdf: 327861 bytes, checksum: 10b3c4ac9c1fb002cc94c4da4da28d0e (MD5) / Made available in DSpace on 2017-04-20T13:00:17Z (GMT). No. of bitstreams: 1 texto completo.pdf: 327861 bytes, checksum: 10b3c4ac9c1fb002cc94c4da4da28d0e (MD5) Previous issue date: 2002-12-03 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A busca de alimentos produzidos sob um sistema de manejo menos agressivo ao meio ambiente vem sendo adotado por um número cada vez maior de produtores. Entretanto, apesar de existirem diversos benefícios na redução ou até eliminação do uso de defensivos, a grande diversidade de doenças em tomateiro (Lycopersicon esculentum Mill.), capazes de limitar a produção, torna necessária a busca por alternativas viáveis, eficientes e tecnicamente comprovadas. Dentre os organismos mais estudados, bactérias têm sido relatadas como agentes de biocontrole capazes de atuar por meio de mecanismos como antibiose, parasitismo, competição e indução de resistência. O presente trabalho teve como objetivos selecionar bactérias do filoplano do tomateiro, baseado em uma estratégia de seleção in vivo, verificando se há um método de isolamento que permita obter antagonistas eficientes no controle da pinta-preta, causada por Alternaria solani, requeima por Phytophthora infestans, mancha-bacteriana pequena por Pseudomonas syringae pv. tomato e mancha-bacteriana por Xanthomonas vesicatoria. Objetivou ainda estudar a possibilidade dos mecanismos de antibiose e indução de resistência serem responsáveis pelo controle destas doenças e se testes de antibiose in vitro são adequados como critério de seleção. Caracterizar aspectos biológicos dos antagonistas que podem otimizar sua aplicação como agente de biocontrole. Determinar a quais produtos antimicrobianos os isolados são insensíveis, visando fornecer subsídios para o desenvolvimento de meios semi-seletivos e estudos de dinâmica populacional. Verificar sua compatibilidade com antibióticos e fungicidas registrados para o controle de enfermidades do tomateiro, a fim de inseri-lo no sistema de manejo integrado e estudar a eficiência de antagonistas selecionados em condições de campo. Os resultados demonstram que, em folíolos mais jovens, os métodos de isolamento que visam obter bactérias da população total e da superfície do filoplano, foram os que permitiram obter a maioria dos antagonistas. O único obtido de folíolos mais velhos foi proveniente da população capaz de habitar sítios protegidos do filoplano e/ou resistir a fatores de estresse. Não se observou relação entre características biológicas dos antagonistas e dos patógenos testados. Nos testes de antibiose com os antagonistas selecionados, o isolado UFV-STB 6 foi capaz de produzir compostos voláteis e inibir a germinação de cistos de Phytophthora infestans, o que possivelmente deve estar envolvido no controle da requeima. O isolado UFV-IEA 6 produziu quitinase, havendo uma tendência em reduzir a taxa de crescimento de Alternaria solani por compostos voláteis. Ficou demonstrado que os testes de antibiose in vitro são inadequados como critério para seleção de agentes de biocontrole do filoplano de tomateiro. A caracterização dos melhores antagonistas demonstrou que três são bactérias Gram-positivas, em forma de bastonete, e uma Gram-negativa, pleiomórfica. Dentre as Gram-positivas todas são anaeróbias facultativas e uma forma endósporos. Nenhum antagonista foi capaz de causar reação de hipersensibilidade (HR) em fumo e produzir pigmento fluorescente in vitro. Os períodos de geração calculados a partir das curvas de crescimento revelaram que três isolados são capazes de se multiplicar rapidamente em meio de cultura, o que é uma característica desejável. Os resultados obtidos a partir dos antibiogramas, mostraram que existem antibióticos que podem ser utilizados para elaboração de meios semi-seletivos, adequados a cada antagonista e os testes de compatibilidade com antibióticos e fungicidas utilizados na cultura do tomateiro revelaram que os antagonistas podem ser expostos aos fungicidas benomyl, enxofre, dimetomorph e tiofanato-metílico. Verificou-se também a inadequação de se utilizarem compostos antimicrobianos em meio de cultura para isolamento de agentes bacterianos de controle biológico, uma vez que os antagonistas selecionados foram sensíveis à maioria dos produtos testados. Os testes com as enzimas indicadoras do estado de indução de resistência, β-1,3-glucanases, Fenilalanina amônia-liase (PAL), Peroxidases (PO), Polifenoloxidases (PPO) e Lipoxigenases (LOX), indicaram que o isolado UFV-IEA 6 foi capaz de promover aumento significativo na atividade das PO, evidenciando a possibilidade do antagonista agir como indutor de resistência. Esse parece ser o primeiro caso que se tem conhecimento de uma bactéria não fitopatogênica do filoplano induzindo resistência na mesma cultura de onde foi obtida. Os testes com os dois antagonistas em condições de campo demonstraram que UFV-STB 6 foi o mais eficiente em reduzir a severidade da requeima no terços médio e superior das plantas, enquanto UFV-IEA 6, somente no terço superior. Houve tendência na redução do progresso da septoriose por UFV-STB 6 e capacidade em diminuir o número de frutos com sintomas de requeima. Os resultados demonstram o potencial de uso dos agentes de biocontrole selecionados para as doenças da parte aérea de tomateiro estudadas. / Farmers are increasingly adapting environmentally less aggressive management systems for food production and there are many benefits in reducing or even eliminating pesticide use. Due to a large number of production limiting diseases on tomato (Lycopersicon esculentum), it is desirable to find technically viable and proven alternatives for their control. Among the microorganisms, bacteria have been reported as biocontrol agents capable of acting through antibiosis, parasitism, competition and induced resistance. The present study aimed at selecting the tomato phylloplane bacteria, based on in vivo isolation strategy, and to determine if this method permits obtaining efficient antagonists to control Alternaria solani leaf spot, Phytophthora infestans blight, small bacterial leaf spot caused by Pseudomonas syringe pv tomato, and bacterial leaf spot caused by Xanthomonas vesicatoria. The study also aimed at determining mechanisms of action, such as antibiosis and induced resistance, involved in disease control, and to determine if the antibiosis tests are sufficient selection criteria. The study also included biological characterization of the antagonists that may optimize their use. To help develop selective or semi-selective media for population dynamic studies, insensitivity of selected isolates to some antimicrobial compounds was also determined. The compatibility of select antagonists with antibiotics and fungicides registered for control of tomato diseases was elucidated so that the antagonist can be inserted in the integrated management. Field studies were done to determine the efficiency of select antagonists. The isolation method that obtain total bacterial population from the phylloplane of the young leaflets permitted obtaining maximum number of antagonists. The only one isolate obtained from the older leaflets originated from the population capable of inhabiting protected sites of phylloplane and/or that resist stress factors. There was no relation between biological characteristics of the antagonists and of the pathogen tested. In the antibiosis testes, the isolate UFV-STB 6 produced volatile compounds that inhibited germination of P. infestance cyst and may be involved in the control of blight. The isolate UFV-IEA 6 produced chitinase and showed a tendency to reduce A. solani growth by the volatile compounds. In vitro antibiosis testes were inadequate criteria to select biocontrol agents from tomato phylloplane. The characterization of promising antagonists showed that three were Gram positive bacilli and one was gram negative pleiomorphic bacteria. Among the Gram positives all were facultative anaerobes and the one formed endospores. None of the antagonists caused hypersensitive reaction (HR) in tobacco, and did not produce fluorescent pigment in vitro. The generation period calculated from the growth curve revealed that three isolates are capable of multiplying rapidly in the culture media, which is a desirable characteristic. The antibiograms showed that there are antibiotics that can be used for elaboration of semi-selective media for each of antagonists and the compatibility testes with antibiotics and fungicides used on tomato crop revealed that the antagonists can be exposed to fungicides such as benomyl, sulfur, dimethomorph and thiophante-methyl. Many antimicrobial compounds were inhibitory to the selecte antagonists in culture media used for isolation of bacterial biocontrol agents, therefore were inadequate for use in selective media. The analysis of enzymes involved in induced resistance, like -1,3-gluconase, phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and lipoxigenase (LOX), showed that the isolate UFV-IEA 6 was capable of increasing PO activity, showing the possibility of being a resistance inducer . This appears to be the first case of a non-pathogenic phylloplane bacterium inducing resistance in a plant of origin. The field testes with two antagonists, UFV-STB 6 was more efficient in reducing the blight severity in the middle and upper third of the plant, while UFV-IEA 6 only in the upper third. The latter isolate also showed a tendency for reducing the Septoria leaf spot progress and the number of fruits with the blight symptoms. The results showed these isolates have the potential of use to control tomato diseases of aerial parts. / Tese importada do Alexandria