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

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.

Doctor of Philosophy / Department of Plant Pathology / Megan Kennelly / Large patch, caused by the fungus Rhizoctonia solani anastomosis group (AG) 2-2 LP, is the most common and severe disease of zoysiagrass (Zoysia spp). Despite the importance of this disease, few studies have examined pathogen biology, cultivar susceptibility, cultural controls, and chemical controls. The objectives of this dissertation were: (1) Characterize large patch isolates based on anastomosis pairing, in-vitro mycelial growth rates, nuclear counts, virulence, PCR, and amplified fragment length polymorphism (AFLP); (2) Determine the effects of cultivation (aerification, verticutting, and sand topdressing) on disease severity; (3) Evaluate different fall and spring applications of the fungicides flutolanil, azoxystrobin, and triticonazole; (4) Evaluate the susceptibility of fifteen new zoysiagrass germplasm lines from parental crosses including Z. japonica, Z. matrella, and Z. pacifica. All the R. solani isolates from large patch-infected zoysiagrass from Kansas belonged to AG 2-2 LP. Variations were observed among the isolates in their average number of nuclei per cell, mycelial growth rates and virulence. There was also variation in the amplified fragment length polymorphism (AFLP) DNA fingerprints, suggesting possible underlying genetic differences of biological significance among members of AG 2-2 LP. Cultivation did not affect soil moisture or temperature. Cultivation also did not reduce patch sizes, nor influence turf recovery rate from large patch. From 2009 to 2011, spring and fall N fertility was consistently associated with lower percentages of diseased turf in both cultivated and non-cultivated plots at Manhattan and Haysville. In general, two fall applications of fungicide did not reduce disease compared to one fall application. Fungicides applied in the fall when thatch temperatures ranged from 17.8oC to 23.2oC reduced disease compared to untreated controls. Early spring applications reduced disease compared to later spring applications. In germplasm screening studies, all progeny had similar disease levels compared to Meyer in the growth chamber, but only 6 consistently had disease levels as low as Meyer in the field. Growth chamber results did not correlate to field results.

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.

Inoculation with free-living diazotrophic bacteria is well documented to enhance vegetative growth and yield increases of various crops coupled with suppression of sublethal pathogens. The use of microbial inoculants has been identified as an alternative or supplement to use of nitrogenous fertilizers and agrochemicals for sustainable agriculture. The search for effective free-living diazotrophic bacterial strains for formulation as biofertilizers has been on going since the 1970’s and a number of inoculant biofertilizers have been developed and are commercially available. In the current study, 250 free-living diazotrophic bacteria were isolated from soils collected from the rhizosphere and leaves of different crops in different areas within KwaZulu-Natal, province, Republic of South Africa. These were evaluated for plant growth-promotion and biological control of damping-off fungi initially by in vitro screening. The growth promotion traits tested included, phosphate-solubilization, production of indole-3-acetic acid, production of ammonia and acetylene reduction. Biocontrol traits evaluated included siderophore-production, antibiosis, and production of hydrogen cyanide (HCN). Biochemical and molecular bioassay tests were conducted to identify the twenty most promising isolates selected in the in vitro study. The twenty isolates were further tested in combination with various levels of nitrogenous fertilizer for growth-promotion of maize (Zea mays L.) and wheat (Triticum aestivum L.) under greenhouse conditions. The five most promising isolates identified for growth promotion under greenhouse conditions for each crop were assessed for their effects on the germination of maize in vitro and growth and yields of two maize and two wheat cultivars, when combined with a low dose of nitrogenous fertilizer in field trials. The five Bacillus subtilis (Ehrenberg) Cohn isolates that suppressed the growth of a wide range of pathogenic fungi in vitro were tested for their efficacy against damping-off of wheat caused by Rhizoctonia solani Kühn in the greenhouse. These isolates were further studied for their modes of action against R. solani in vitro. The modes of action tested included antibiosis, production of siderophores, extracellular enzymes, production of hydrogen cyanide (HCN) and antibiotic resistance. The twenty most promising bacterial isolates identified from the in vitro screening reduced acetylene to ethylene, produced indole-3-acetic acid and siderophores, one isolate solubilized phosphate, and 9 inhibited the growth of R. solani. These twenty isolates enhanced growth of maize and wheat above the Uninoculated Control under greenhouse conditions. The growth enhancements varied with bacterial isolate x crop species interactions, which identified five different isolates for each of the two crops. Relative to the Uninoculated Control, the best five isolates significantly (P = 0.001) enhanced the growth of maize and wheat at all fertilizer levels for a number of growth parameters: increased chlorophyll levels and heights of maize, shoot dry biomass of maize and wheat, and enhanced root development of maize in the greenhouse. Inoculation of maize and wheat with the two most promising isolates identified from the field trial for each crop, in combination with 65% and 50% of the recommended amount of nitrogenous fertilizer for maize and wheat, respectively, caused the same increases in shoot biomass as the Fully Fertilized Control. Application of a combination of the best bacterial isolates and 35% nitrogenous fertilizer resulted in the same or greater shoot dry biomass and yields of both maize and wheat under field conditions. Shoot dry biomass of wheat increased by 75% above the Uninoculated Control and 30% above the Fully Fertilized Control. The wheat yield increased by 95% above the Uninoculated Control and 43% above the Fully Fertilized Control. Seed inoculation with the best isolates combined with 35% N increased yields of maize by 41% above the Uninoculated Control and 15% above the Fully Fertilized Control. The best isolates significantly (P < 0.001) increased plant height, chlorophyll levels and shoot biomass of maize relative to the Uninoculated Control. There was a positive correlation between chlorophyll level and yield, chlorophyll level and shoot dry biomass, height and shoot dry biomass and height and yield of maize at P = 0.01 with r values of 0.87, 0.77, 0.92 and 0.81, respectively. The isolates that exhibited multiple plant-growth promoting traits in vitro, increased shoot biomass of both maize and wheat in the greenhouse and field, and caused yield increases in the two crops under field conditions. Five B. subtilis isolates inhibited the growth of some of the pathogenic fungi tested in vitro up to 95%. Seed inoculation with the same isolates significantly (P = 0.001) suppressed R. solani damping-off of wheat under greenhouse conditions and exhibited multiple mechanisms of disease control in vitro. The use of microbial inoculants in combination with low doses of nitrogenous fertilizers can enhance crop production without compromising the yields. The B. subtilis isolates obtained in this study can effectively control R. solani damping-off of wheat, fix nitrogen and enhance plant growth. The use of microbial inoculants can contribute to the integrated production of cereal crops with reduced nitrogenous fertilizer inputs, as a key component of sustainable agriculture. Key words: Free-living bacteria; plant growth-promotion; diazotrophs; biological nitrogen fixation; phosphate-solubilization; siderophores; indole-3-acetic acid; biocontrol; damping-off / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Orientador: Paulo Cezar Ceresini / Resumo: O controle biológico é um dos métodos do manejo integrado de doenças de plantas, sendo uma das únicas alternativas viáveis para minimizar o impacto da queima-das-folhas e morte súbita das pastagens do gênero Urochloa (anteriormente Brachiaria). A queima-das-folhas e morte de pastagens é causada pelo fungo basidiomiceto Rhizoctonia solani grupo de anastomose AG-1 IA. Em nosso estudo determinamos se isolados de espécies de Pseudomonas fluorescentes obtidos de solos supressivos do bioma Amazônico possuem potencial como agentes de biocontrole de R. solani AG-1 IA. Especificamente objetivamos: i. Efetuar o screening de isolados de Pseudomonas quanto ao potencial de biocontrole in vitro; ii. Realizar a identificação molecular dos isolados de Pseudomonas fluorescentes selecionados como potenciais agentes de biocontrole e iii. Determinar se as bactérias selecionadas in vitro mantém, in vivo, o potencial de biocontrole da queima-das-folhas e morte da braquiária. Três isolados foram selecionados como potenciais agentes biocontroladores nos testes de antagonismo in vitro (Amana, Poti e Yara), pois diminuíram significativamente tanto o crescimento micelial quanto a germinação de escleródios do patógeno. Com base em análises filogenéticas, os isolados Amana e Yara foram agrupados ao clado de Pseudomonas putida enquanto o isolado Poti foi agrupado em clado distinto de todos os demais, e possivelmente se constitui numa nova espécie. Nos testes in vivo, a inoculação via sementes não resultou... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Biological control is one of the methods of the integrated management of plant diseases, which is one of the only viable alternative to minimizes foliar blight impact and sudden death of pastures from genus Urochloa (previously known as Brachiaria). Foliar blight and death of pastures are caused by the fungus Rhizoctonia solani AG-1 IA. In our study, it was determined whether isolates from florescent Pseudomonas obtained from suppressive soils on the Amazon biome had potential as biocontrol agents of Rhizoctonia solani AG-1 IA. Specifically, we aim to: i. Carry out a screening of isolates from Pseudomonas to evaluate their potential as in vitro biocontroler; ii. Perform molecular identification of selected fluorescent Pseudomonas isolates as potential biocontrol agents; and iii. Determine whether in vitro selected bacterial strains maintain the biocontrol ability in vivo of foliar blight and sudden death of braquiária. Three isolates were selected as potential biocontoller agents in vitro antagonism tests (Amana, Poti e Yara), which reduced significantly mycelial growth and sclerotia germination of pathogen. Based on phylogenetic analyzes, Amana and Yara isolates were grouped to the clade belonging to Pseudomonas putida and Poti isolated was grouped in a distinct clade, and should to constitute a new species. For in vivo tests, seed inoculation did not resulted in R. solani AG-1 IA control. On the other hand, in foliar application of biocontrol agent, Amana isolated was the m... (Complete abstract click electronic access below) / Mestre

Resumo: O fungo Thanatephorus cucumeris é responsável por várias doenças foliares em culturas de importância agrícola ou em espécies nativas na região Amazônica do país. Entre as doenças relatadas, a mancha areolada de Thanatephorus é considerada uma das mais importantes para a região. Neste estudo, baseando-se na ausência de informações sobre quais os grupamentos de anastomose (AG) de Rhizoctonia solani estão associados a plantas hospedeiras na Amazônia, foi testada a hipótese de que os isolados de T. cucumeris oriundos de seringueira e citros e outras espécies cultivadas ou nativas pertencem a grupamentos de anastomose distintos. Assim, os isolados de T. cucumeris foram caracterizados citomorfologicamente, por meio da caracterização cultural, grupamento de anastomose e molecular. Esta última baseou-se na observação da variação associada a seqüências da região ITS-5,8S do rDNA. Também não há informação sobre a patogenicidade cruzada, à seringueira, de isolados provenientes de outras espécies de plantas da Amazônia. Então, por meio do teste de patogenicidade cruzada foi testada uma segunda hipótese, a de que isolados de T. cucumeris de hospedeiros distintos são patogênicos também à seringueira. O estudo teve como objetivo elucidar aspectos importantes sobre a etiologia do patógeno, que podem ser relevantes para o manejo da doença. De forma importante, concluiu-se que a seringueira hospeda não apenas um, mas sim vários grupos de anastomose de R. solani como agente causal da mancha areolada. / Abstract: The fungus Thanatephorus cucumeris is responsible for causing several foliar diseases on important agricultural crops or on native species in the Amazonian area of the country. Among the diseases, Thanatephorus aerial blight is considered one of the most important in that region. In this study, based on the lack of information on which anastomosis groups (AG) of R. solani are associated with distinct hosts in the Amazon, we tested the hypothesis that T. cucumeris isolates from rubber tree, citrus and other cultivated or native species from the area belong to distinct AGs. So, T. cucumeris isolates were characterized based on cytomorphology, cultural characteristics, by anastomosis grouping, and molecularly. This last one was based on the observation of the variation associated with sequences of the ITS-5.8S region of the rDNA. There is no information about the cross pathogenicity (to rubber tree) of isolates from other Amazonian plant species. Based on cross-pathogenicity tests, a second hypothesis was tested stating that T. cucumeris isolates from distinct hosts are also pathogenic to rubber tree. This study had as objective to elucidate important aspects of the aetiology of the pathogen that can be relevant for managing the disease. We have found that the rubber tree hosts not only one, but several anastomosis groups of R. solani as causal agent of the aerial blight. / Orientador: Paulo Cezar Ceresini / Coorientador: Alcebíades Ribeiro Campos / Banca: Edson Luiz Furtado / Banca: Cesar Junior Bueno / Mestre