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In this study, we have demonstrated that inoculation of bean seeds with non-pathogenic binucleate Rhizoctonia (np-BNR) at sowing protected bean seedlings from infection of R. solani. Using quantitative real-time RT-PCR (QRT-PCR), transcript levels of defense genes encoding 1,3-beta-glucanase (GLUC), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) in one-week old bean seedlings was monitored during np-BNR and R. solani interaction. The results revealed that protection effect of np-BNR correspond to a systemic suppression of these three defense genes' expression from significant higher level elicited by R. solani to the level of non-infected plants. This indicates that bio-protection by np-BNR isolates is not correlated to activation of these three defense genes' expression. Similar suppression was achieved for pre-colonization of bean seedlings with arbuscular mycorrhizal (AM) Glomus introradices on GLUC gene expression, although the AM fungus did not significantly reduce rot symptoms. Possible mechanisms implicated in down-regulation during plant-pathogen and np-BNR or AM interaction are discussed.

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.

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.

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?

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

Made available in DSpace on 2014-06-11T19:32:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-31Bitstream added on 2014-06-13T20:23:19Z : No. of bitstreams: 1 molina_lmr_dr_jabo.pdf: 480341 bytes, checksum: b838d0062518eb208c7e881bd5eb7588 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / No início dos anos 90, o fungo Rhizoctonia solani emergiu como um patógeno importante associado à morte de pastagens do gênero braquiária na Colômbia. Inicialmente, esse estudo indicou que R. solani AG-1 IA predomina como patógeno associado à queima da folha da braquiária nos Llanos Colombianos. Para o estudo da estrutura genético-populacional do patógeno, um total de 198 isolados de R. solani AG-1 IA foram coletados de campos de B. brizantha cv. Toledo, de Brachiaria híbrido Mulato e do arroz. Os isolados foram genotipados usando dez loci microssatélites. Um sistema reprodutivo misto (reprodução sexuada e clones adaptados) caracterizou as populações de R. solani AG-1 IA que infectam a braquiária. A alta fração clonal e os desvios do equilíbrio de Hardy-Weinberg encontrados foram consistentes com o efeito Wahlund associado à mistura de populações. Padrões históricos de migração entre populações hospedeiro-distintas indicaram a origem provável das populações que infectam braquiária a partir de populações que infectavam arroz. Para determinar o efeito do estresse térmico na evolutibilidade para crescimento micelial, populações de R. solani AG-1 IA infectando braquiária ou arroz e R. oryzae-sativae do arroz, foram submetidas à temperatura ótima e de estresse (25 e 35°C). A herdabilidade para crescimento micelial sob condições de estresse foi considerada alta na população de R. oryzae-sativae do arroz, indicando que os patógenos têm potencial de adaptação à temperatura de 35°C / In the early '90s, the fungus Rhizoctonia solani has emerged as an important pathogen associated with the death of Brachiaria pastures in the Colombian Llanos. Initially, this study indicated that R. solani AG-1 IA was the predominant pathogen associated with the leaf blight in the Colombian Llanos. To study the population genetic structure of the pathogen, a total of 198 isolates of R. solani AG-1 IA were collected from fields of B. brizantha cv. Toledo, Brachiaria Mulato hybrid and from rice. These isolates were genotyped using ten microsatellite loci. A mixed mating system (sexual reproduction and dispersal of adapted clones) characterized the populations of R. solani AG-1 IA infecting Brachiaria. The high clonal fraction and deviations from Hardy-Weinberg equilibrium found in three out of four populations were consistent with Wahlund effect associated with the mixing of populations. Historical patterns of migration between different host-populations indicated that the likely source of the current populations infecting Brachiaria in the Colombian Llanos was from populations that originally infected rice. To determine the effect of heat stress on the evolvability for mycelial growth, two host distinct populations of Rhizoctonia solani AG-1 IA infecting either brachiaria or rice and a rice-infecting population of R. oryzae-sativae, were submitted to optimal and stress temperatures (25°C and 35°C). The heritability values for mycelial growth under heat stress was considered high for rice-infecting population of R. oryzae-sativae, indicating that these pathogen’s population have a high potential to adapt to 35°C temperature

Made available in DSpace on 2014-06-11T19:29:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-06-13Bitstream added on 2014-06-13T19:18:06Z : No. of bitstreams: 1 basseto_ma_me_ilha.pdf: 949120 bytes, checksum: dd3f3b104d600fa3d0cc25023fb35d18 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / 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. / 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.