Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Please read the abstract in the dissertation / Dissertation (MSc)--University of Pretoria, 2011. / Genetics / unrestricted

Bacterial wilt caused by Ralstonia solanacearum has affected the potato industry in South Africa since 1914. Control of bacterial wilt is difficult and depends greatly on integrated management strategies. Little information is available on the longevity of R. solanacearum in soil under South African conditions and how it is influenced by cultural practices. Information regarding local weeds which can serve as alternative hosts is limited. Soil survival of R. solanacearum biovar 2 (race 3) was investigated in an artificially infested field managed by either one of four cultural practices, namely maize and potato monoculture, bare and weed-fallow. After a five-year period wilting of indicator plants was observed in all treatments with potato the highest, followed by bare-fallow, maize monoculture and lastly weed-fallow. Results demonstrated a greater ability of biovar 2 to survive in soil than generally accepted. Subsequently, the susceptibility of 22 weed and three grass species was investigated in the greenhouse. Five species were susceptible to biovar 2 and 13 to biovar 3. Preliminary in vitro studies conducted to determine suppressiveness of some weeds/grasses, indicate that microbial activity associated with some weeds could be involved in suppression of the wilt organism. Further studies are however required. The effect of maize on Ralstonia solanacearum populations was evaluated in a pot trial as well as in hydroponic culture. Results indicated that microbial populations present in the maize plant, could play a role in the susceptibility of maize to bacterial wilt infection. Antagonistic bacteria associated with some maize plants or with the maize rhizosphere could be partly responsible for suppression of wilt. / Dissertation (MSc Agric (Agronomy))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

Ph.D. (Biochemistry) / Please refer to full text to view abstract

Over the past decade, the Eastern Shore of Virginia (ESV) has been implicated in at least four outbreaks of Salmonellosis associated with tomato all originating from the same strain, Salmonella enterica serovar Newport.  In addition to S. Newport contamination, the devastating plant disease, bacterial wilt, caused by the phytopathogen Ralstonia solanacearum threatens the sustainability of ESV tomato production.  Bacterial wilt is present in most ESV tomato fields and causes devastating yield losses each year.  Due to the ESV\'s endemic population of R. solanacearum and S. Newport, the relationship between the two pathogens is of interest and has never been investigated.  Two separate studies were conducted to assess the relationship between these two bacteria.  One study consisted of a series of greenhouse trials that involved root-dip inoculations of tomato plants with one of four treatments: 1) S. Newport, 2) R. solanacearum, 3) a co-inoculation of S. Newport + R. solanacearum, and 4) a control group with no inoculation. Leaf, stem, and fruit samples were collected from the plants and S. enterica presence from the internal tissues was observed.  S. enterica was recovered from a low percentage of fruit and leaf samples.  There were significantly more stem samples from plants co-inoculated with S. Newport + R. solanacearum positive for S. enterica (17.46%) than from other treatments.  Another study examined the relationship between the two bacteria via vacuum infiltration inoculations of tomato fruit collected from commercial production fields on the ESV with S. Newport.  Tomato fruit were collected from plants expressing symptoms of bacterial wilt (symptomatic) and plants not expressing bacterial wilt symptoms (asymptomatic).  After fruit infiltration with S. Newport, recovery concentration of S. enterica from internal tissues was measured.  S. enterica populations were greater in fruit originating from asymptomatic (5.15 log CFU/g) versus symptomatic (4.91 log CFU/g) plants across five studies.  Fruit collected from asymptomatic plants had a significantly higher internal pH (4.60) than fruit collected from symptomatic plants (4.37).  These results suggest that R. solanacearum can influence S. enterica survival and transportation throughout the internal tissues of tomato plants as well as the influence internal tomato fruit pH, which could potentially impact S. Newport survival in the fruit. / Master of Science in Life Sciences

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-02-21T13:35:42Z No. of bitstreams: 1 Christtianno de Lima Rollemberg.pdf: 2445206 bytes, checksum: 4da0aaed00880d13a23b17cdb6cae239 (MD5) / Made available in DSpace on 2017-02-21T13:35:42Z (GMT). No. of bitstreams: 1 Christtianno de Lima Rollemberg.pdf: 2445206 bytes, checksum: 4da0aaed00880d13a23b17cdb6cae239 (MD5) Previous issue date: 2013-04-30 / This study evaluated the use of silicon (Si) in micropropagation of banana 'Silk' and 'Pacovan Ken' aiming to reduce the severity of fusarium wilt caused by Fusarium oxysporum f. sp. cubense and moko disease caused by Ralstonia solanacearum race 2. The banana plantlets were produced in vitro by adding calcium silicate and potassium silicate (0, 0.25, 0.5, 0.75 and 1 g L-1) to MS medium in the phases of multiplication and rooting. After in vitro culture, the plants were transferred to plastic tubes containing substrate plus the same sources of Si, and maintained in a greenhouse for 45 days, when they were inoculated with the pathogens. With respect to fusarium wilt in cultivars Silk and Pacovan Ken, the elevation of Si increased the incubation period (IP) and reduced the disease index (DI) and area under the disease progress curve (AUDPC). In cultivar Silk but not in Pacovan Ken calcium silicate was significantly more effective than potassium silicate. In shoots and roots of both cultivars in both sources, before and after acclimatization Si concentration was greater at a dose of 1.0 g L-1 compared to the control without Si. Before acclimatization, calcium silicate provided higher Si concentration in the shoots than potassium silicate. The opposite happened with the Si concentration in the roots. After acclimatization, there was no difference between the calcium silicate and potassium silicate, for both cultivars. In general, for both cultivars and sources of Si there were positive correlations with the concentration of Si and IP, and negative correlations with DI and AUDPC. Before and after acclimatization, the anatomical variable of roots: thickness of the root epidermis, cortex, endodermis and central cylinder of banana 'Silk' and 'Ken Pacovan' were influenced by Si sources. Calcium silicate was more efficient in increasing the thickness of the root epidermis, cortex and central cylinder, while potassium silicate was more efficient in thickening of the endodermis. In general, there were positive correlations among anatomical variable of roots with PI and negative correlations with DI and AUDPC, except for potassium silicate in cultivar Silk. The research conducted with moko disease showed that increase of Si in Silk and Pacovan Ken cultivars caused increase in IP and decreases the DI and AUDPC. At the dosage of 1.0 g L-1 AUCPD was reduced by 27.3%. In cultivar Silk, calcium silicate was more effective than potassium silicate (P≤0.05), while in „Pacovan Ken‟ there was no difference. In both cultivars, plants treated with Si showed, in general, concentrations of chlorophylls a, b and total higher than plants Si- up to six days after inoculation, which may have influenced the disease IP. In general, both the enzymes related to oxidative stress (CAT, SOD and APX), as the plant defense (POX, PPO, CHI and GLU), had increased its activities in plants treated with Si, especially those with calcium silicate, indicating a possible role in reducing the severity of the disease. The supply of Si in micropropagation of banana 'Silk' and 'Pacovan Ken' promoted reduction of Fusarium wilt and moko disease, and therefore can be used as a new technology in the management of these diseases. / Este estudo avaliou o uso do silício (Si) na micropropagação de bananeira „Maçã‟ e „Pacovan Ken‟ visando a redução da severidade da murcha-de-fusário, causada pelo Fusarium oxysporum f. sp. cubense e do moko da bananeira causado por Ralstonia solanacearum raça 2. As mudas de bananeira foram produzidas in vitro com adição de silicato de cálcio e silicato de potássio (0; 0,25; 0,5; 0,75 e 1 g L-1) ao meio de cultivo MS nas fases de multiplicação e enraizamento. Após o cultivo in vitro, as plantas foram transferidas para tubetes contendo substrato acrescido das mesmas fontes de Si, e mantidas em casa de vegetação por 45 dias, quando foram inoculadas com os patógenos. Com relação à murcha-de-fusário, nas cultivares Maçã e Pacovan Ken, a elevação das doses de Si aumentou o período de incubação (PI) e reduziu o índice de doença (IDO) e a área abaixo da curva de progresso da doença (AACPD). Em „Maçã‟ o silicato de cálcio foi significativamente mais eficiente que o silicato de potássio, o que não ocorreu na „Pacovan Ken‟. A concentração de Si na parte aérea e raízes das cultivares, em ambas as fontes, antes e após a aclimatização foi maior na dose de 1,0 g L-1 em relação à testemunha sem Si. Antes da aclimatização, o silicato de cálcio proporcionou maior concentração de Si na parte aérea que o silicato de potássio. O contrário aconteceu com a concentração de Si nas raízes. Após aclimatização, não houve diferença entre o silicato de cálcio e o silicato de potássio, para as duas cultivares. Em geral, para ambas as cultivares e fontes de Si foram observadas correlações positivas da concentração de Si com PI e correlações negativas com IDO e AACPD. Antes e após a aclimatização das plantas, as espessuras da epiderme radicular, córtex, endoderme e cilindro central das bananeiras „Maçã‟ e „Pacovan Ken‟ foram influenciadas pelas fontes de Si. O silicato de cálcio foi mais eficiente no aumento da espessura da epiderme radicular, córtex e cilindro central, enquanto o silicato de potássio foi mais eficiente no aumento da espessura da endoderme. Em geral, foram observadas correlações positivas das variáveis anatômicas das raízes com PI e correlações negativas com IDO e AACPD, exceto para silicato de potássio em bananeira „Maçã‟. Na pesquisa desenvolvida com o moko da bananeira, a elevação das doses de Si nas cultivares Maçã e Pacovan Ken causou aumento no PI e reduções do IDO e AACPD. Na dosagem de 1,0 g L-1, a AACPD foi reduzida em até 27,3%. Em bananeira „Maçã‟ o silicato de cálcio foi mais eficiente que o silicato de potássio (P≤0,05), enquanto na „Pacovan Ken‟ não houve diferença. Nas duas cultivares, plantas tratadas com Si apresentaram, de maneira geral, concentrações de clorofilas a, b e total maiores que as plantas Si- até os seis dias após inoculação, o que pode ter influenciado o PI da doença. Em geral, tanto as enzimas relacionadas ao estresse oxidativo (CAT, SOD e APX), quanto as de defesa da planta (POX, PFO, GLU e QUI), tiveram suas atividades aumentadas nos tratamentos com silício, especialmente naqueles com silicato de cálcio, indicando uma possível participação na redução da severidade da doença. O fornecimento de Si na micropropagação de bananeiras „Maçã‟ e „Pacovan Ken‟ promoveu redução da murcha-de-fusário e moko da bananeira, podendo ser utilizado como uma nova tecnologia no manejo dessas doenças.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-14T15:38:58Z No. of bitstreams: 1 Katia Cilene da Silva Felix (1).pdf: 376089 bytes, checksum: 45b421012fb39c4ea534d1182006970e (MD5) / Made available in DSpace on 2017-03-14T15:38:58Z (GMT). No. of bitstreams: 1 Katia Cilene da Silva Felix (1).pdf: 376089 bytes, checksum: 45b421012fb39c4ea534d1182006970e (MD5) Previous issue date: 2009-02-18 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Bacterial wilt caused by Ralstonia solanacearum, race 1, biovars 1 and 3 causes severe damage to pepper growth in Agreste region of state of Pernambuco in Brazil. The pathogen survival in infected tissues of stem and roots incorporated to the soil at 0, 5 and 15 cm; and at 10 different soil types of Pernambuco without host plant was studied by using a spontaneous mutant resistant to 100 mg l-1 of rifampicin (R. solanacearum A1-9Rif). Pathogen survival only showed difference (P<0.05) in relation to vegetal tissue. Pepper root tissues showed higher survival duration (DUR) (17.1 d), area under population curve (AACPOP) (430x104) and population at 7 (POP7) (5.0x104 UFC g-1 tissue) and 21 days (POP21) (3.1x104 UFC g-1 tissue) than stem tissues, which were respectively, 7.0 d; 3.8 x104; 0.35 and 3.1x104 UFC g-1 tissue. On the other hand stem tissues presented higher decomposition index (81.3%) and pH (7.7) than root tissues, respectively 68.9% and 6.8. The previous soil microbiological analysis did not finddifferences among populations of actinomycetes, copiotrophic, bacteria, total bacteria and total fungi respectively 5.02; 3.63; 5.23 and 4.19 log UFC g-1 dry soil. Populations of oligotrophyc bacteria, Bacillus spp., fluorescent Pseudomonas spp. and Trichoderma spp. were not detected. The pathogen was isolated from the soil adjacent to infected tissues of stem and roots at the three depths six weeks after experiment establishment. The analysis of AACPOP in relation to locals (counties) of soil sampling, type of soil coverage at the sampling time and soil texture was not significant by Kruskal-Wallis test (P≤0.05). Among the 10 studied soils, seven were classified as suppressive showing low intervals of DUR (42 to 49 days), AACPOP (0.77 to 4.05), POP14 (5.59 to 6.18 log UFC g-1 soil) and POP42 (5.44 to 6.31 log UFC g-1 soil). The soils S3, S4 and S6 were evaluated as conducive. Considering all soils together or only the suppressive, DUR,AACPOP and POP42 only showed significant correlation with soil physical and chemical characteristics, positive for clay, residual humidity and useful water and negative for pH. The population of copiotrophic bacteria, actinomycetes, total bacteria, total fungi (Fusarium spp., Aspergillus spp., Penicillium spp. and Rhizopus spp. were identified) and Bacillus spp. did not differ among the 10 soil types. / A murcha-bacteriana do pimentão é causada por Ralstonia solanacearum, raça 1, biovares 1 e 3 e causa grandes prejuízos à cultura desta solanácea. Este trabalho teve por objetivo estudar a sobrevivência do patógeno em tecidos infectados de caule e raiz incorporados ao solo às profundidades de 0, 5 e 15 cm; e em 10 diferentes tipos de solo na ausência da planta hospedeira. Foi utilizado um mutante resistente a 100 mg l-1 de rifampicina (R. solanacearum A1-9Rif). A sobrevivência do patógeno diferiu significativamente (P<0,05) apenas em relação aos tecidos vegetais analisados isoladamente. Desta forma, tecidos de raiz de pimentão apresentaram maior duração da sobrevivência (17,1 d), área abaixo da curva da população (AACPOP) (430x104) e população aos 7 (POP7) (5,0 x 104 UFC g-1 tecido) e 21 dias (POP21) (3,1 x 104 UFC g- 1 tecido) que os de caule, que foram respectivamente, 7,0 d; 3,8; 0,35 x104 e 0,48 x 104UFC g-1 tecido. Por outro lado, os tecidos do caule apresentaram maior índice de decomposição (81,3%) e pH (7,7) do que os de raízes, respectivamente 68,9% e 6,8. A análise microbiológica prévia deste solo não evidenciou diferenças significativas entre as populações de actinomicetos, bactérias copiotróficas, bactérias totais e fungos totais, que foram de 5,02; 3,63; 5,23 e 4,19 log UFC g-1 solo seco, respectivamente. Não foram encontradas populações de bactérias oligotróficas, Bacillus spp., Pseudomonas spp. fluorescentes, e Trichoderma spp. Entre os 10 tipos de solos estudados, sete foram classificados como supressivos por apresentarem baixas duração da sobrevivência (42 a 49 dias), AACPOP (0,77 a 4,05), POP14 (5,59 a 6,18 log UFC g-1 solo) e POP42 (5,44 a 6,31 log UFC g-1 solo). Os solos S3, S4 e S6 foram avaliados como conducivos. Neste estudo, apenas algumas características físicas e químicas apresentaram correlaçãosignificativa com duração da sobrevivência, AACPOP e POP42, considerando todos ossolos em conjunto ou apenas os supressivos, destacando-se argila, umidade residual e água disponível que apresentaram correlação positiva e o pH com correlação negativa.

Made available in DSpace on 2014-06-11T19:28:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-28Bitstream added on 2014-06-13T20:37:45Z : No. of bitstreams: 1 rodrigues_lmr_me_botfca.pdf: 618458 bytes, checksum: cb654c56905a6abeae0bdd7484f37739 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho teve como objetivo avaliar a agressividade de linhagens de Ralstonia solanacearum provenientes de solanáceas, plantas ornamentais e eucalipto, em plantas de batata, tomate e fumo, bem como caracterizar as linhagens por meio de técnicas moleculares. Vinte e duas linhagens foram utilizadas nos ensaios de avaliação da agressividade, em experimentos conduzidos em casa-de-vegetação evidenciaram alta severidade da doença pelas linhagens de R. solanacearum quando inoculadas em plantas de tomate e batata, sendo a batata mais afetada nas inoculações. Todas as linhagens mostraram-se agressivas, sendo que o fumo mostrou baixa suscetibilidade ao ataque das bactérias. As linhagens mais agressivas em plantas de tomate foram IBSBF 309, IBSBF 1712, IBSBF 1839, IBSBF 1882, IBSBF 1883 e IBSBF 2000, pertencentes às biovares I, II e III. As linhagens mais agressivas às plantas de fumo foram IBSBF 309, IBSBF 2131 e IBSBF 292T, pertencentes à biovar I. Foi efetuado também ensaio de microbiolização in vitro em sementes de eucalipto, a fim de se identificar possíveis linhagens patogênicas a esta espécie vegetal e concluiu-se que todas as linhagens utilizadas infectaram plantas de eucalipto ou afetaram seu crescimento. A caracterização molecular de 41 linhagens de Ralstonia solanacearum, provenientes de diversas plantas hospedeiras, incluindo solanáceas, bananeira, helicônia, plantas ornamentais e eucalipto, foi efetuada empregando-se ERIC e BOX-PCR e os resultados mostraram grande diversidade genética entre as linhagens. A análise de PCR-RFLP da região espaçadora 16S-23S DNAr permitiu distinguir os isolados pertencentes à biovar III das demais biovares (I, II, IIA e IIT), quando digeridos com as enzimas Taq I e Hin6 I. A análise de sequenciamento de parte dos genes Endoglucanase (Egl) e MutS possibilitou a classificação em filotipos e os resultados... / This study aimed to evaluate the aggressiveness of strains of Ralstonia solanacearum from solanaceus, ornamental and eucalyptus plants, on potato, tomato and tobacco, and to characterize the strains through molecular techniques. Twenty-two strains were used in this study to evaluate the aggressiveness and, the experiments conducted in a greenhouse revealed the high susceptibility of tomato and potato plants, with the potato being the most affected on through the inoculations. All isolates proved to be aggressive and higher tolerance to the attack of bacteria was verified on tobacco plants. Strains more aggressive on tomato were IBSBF 309, IBSBF 1712, IBSBF 1839, IBSBF 1882, IBSBF 1883 and IBSBF 2000, belonging to biovars I, II and III. The more aggressive strains on the tobacco plants were IBSBF 309, IBSBF 292T and IBSBF 2131 belonging to biovar I. Tests in vitro of microbiolization of eucalyptus seeds were also performed in order to identify possible pathogenic strains to this species and the results showed that all strains used cause infection on emerging plants or affected their growth. To molecular characterization of 41 strains of Ralstonia solanacearum from several host plants including solanaceous, banana, heliconia, ornamentals and eucalyptus were employed to ERIC and BOX-PCR, and the results showed high genetic diversity among strains. The analysis of PCR-RFLP of 16S-23S spacer region rDNA allowed us to distinguish the isolates belonging to biovar III from the others (biovars I, II, IIA and IIT) when digested with enzymes Taq I and Hin6 I. The sequence analysis of the partial of Endoglucanase (Egl) and MutS genes allowed the classification in phylotypes and the results revealed a predominance of the phylotype II in Brazil, and four isolates were classified in the phylotype I, all belonging to biovar III

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-05-13Bitstream added on 2014-06-13T18:45:54Z : No. of bitstreams: 1 silvajunior_taf_dr_botfca.pdf: 1093180 bytes, checksum: 562817be3d67ef9a5b0d63fa5e506cb7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A murcha-de-curtobacterium, causada por Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), é uma das principais doenças bacterianas da cultura do feijoeiro, acarretando grandes perdas na produção dessa cultura. Até o momento existem poucas informações sobre os diferentes nichos de sobrevivência desta bactéria e de sua gama de hospedeiras. Em vista disso, este trabalho teve por objetivos principais verificar a capacidade de sobrevivência saprofítica de Cff em restos de cultura de feijoeiro mantidos na superfície do solo e enterrados à 20 cm de profundidade; a influência da temperatura, umidade e do tipo de solo no período de sobrevivência da bactéria em solo; determinar a gama de hospedeiras de Cff inoculadas artificialmente, tanto por ferimento no caule, como por aspersão de suspensão bacteriana na parte aérea das plantas; a capacidade de colonização de Cff do rizoplano de plantas de aveia e trigo; e o efeito do pré-plantio de aveia e trigo na ocorrência da murcha-de-curtobacterium. Quanto à capacidade de sobrevivência de Cff em restos de cultura de feijoeiro, foi demonstrado que a bactéria possui menor capacidade de sobrevivência quando os restos vegetais são incorporados ao solo e também em épocas com maiores índices de precipitação e temperaturas mais altas. O período de sobrevivência do patógeno nos restos culturais de feijoeiro mantidos na superfície do solo variou entre 165 e 240 dias e nos restos vegetais enterrados a 20 cm de profundidade, o período de sobrevivência foi inferior a 30 dias. Quanto à sobrevivência de Cff na forma de células livres no solo, foi verificado que a temperatura, a umidade e o tipo do solo têm influencia na capacidade de sobrevivência da bactéria. O tempo de sobrevivência de Cff variou entre dois e quinze dias. Das 30 espécies botânicas inoculadas artificialmente com Cff, a bactéria causou lesões na parte... / Bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) is one of the main bacterial diseases affecting bean culture, leading to great losses in its production. So far there is scarce information about the different survival niches and host range of this bacterium. Thus, the present study had as major aims to verify Cff capability of saprophytically surviving in bean debris kept on the soil surface and buried at 20 cm depth; to assess the influence of temperature, humidity and soil type on the survival period of this bacterium in soil; to determine the host range for artificially inoculated Cff, either through stem injury or through bacterial sprinkling onto the shoot of plants; to verify Cff capability of colonizing the rhizoplane of oat and wheat plants; and to assess the effect of oat and wheat pre-planting on the occurrence of bean bacterial wilt. Cff had decreased capability of surviving in bean debris when the latter were incorporated into the soil and during periods of higher rainfall rates and temperatures. The pathogen survival period in bean culture remnants kept on the soil surface ranged from 165 and 240 days, while in plant debris buried at 20 cm depth the survival period was inferior to 45 days. The survival capability of Cff as free cells in soil was influenced by temperature, humidity and soil type. Cff survival time varied between two and fifteen days. Of 30 plant species artificially inoculated with Cff, bean and soy shoot had lesions caused by the bacterium which endophytically colonized wheat leaves and soy and wheat stem and leaves. Cff was also shown to have no capability of colonizing oat and wheat rhizoplane while the pre-planting of these grass plants, before bean culture establishment, had no effect on the occurrence of bean bacterial wilt

Made available in DSpace on 2015-03-26T13:37:48Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1802890 bytes, checksum: 0b75928115b5c4403a010430868a5dbc (MD5) Previous issue date: 2012-02-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ralstonia solanacearum (RS) is a bacterial complex species that causes the bacterial wilt in hundreds of plant hosts, inducing heavy losses mainly on cultivated solanaceus species in tropical and subtropical countries. The race 3 biovar 2 (R3B2) of the pathogen causes not only direct losses but latent infections in many hosts, like the geranium, which facilitates its dissemination in and between countries. In the last decade, it was introduced in USA by infected geranium from Kenya and Guatemala, causing great concerns due the adaptation of this variant to the potato crop. In USA, the R3B2 of RS acquired the status of bioterrorism agent and now faces strong quarantine restrictions in the country. In this work we evaluated the pathogenicity of 36 Brazilian RS strains to geranium, most of them of R3B2. These strains were evaluated to their capacity of infecting geranium (Pelargonium peltatum and P. hortorum), potato and tomato. Seedlings were inoculated by xylem penetration with a pin contaminated at the time of inoculation by touching it onto the selected colony. Ten strains of biovar 1, 22 of biovar 2 and two of biovar 3 were used for comparison proposes. The disease incidence was measured every two days by the percentage of symptomatic plants. The strains were identified in order to analyze the eventual correlations among host of origin, biovar and phylotype. All the five geranium cultivars tested were susceptible, but with different responses among strains. The geraniums were less susceptible than solanaceous hosts tested. Nineteen strains infected one or two of the hosts and 17 infected at least one of the three hosts. The races 1 and 3, biovars 1, 2 and 3, phylotypes I and II, were all capable of infecting geranium. The capacity of R3B2 Brazilian strains to infect the geranium requires special methods for identification and detection of the bacteria in greenhouses for plants produced for export. It was not possible to group the strains according to pathogenic and molecular characteristics; therefore, it is proposed that complete genome analysis be performed to unveil eventual host specificity for some isolates. / Ralstonia solanacearum (RS) é uma espécie bacteriana complexa que causa a murcha bacteriana em centenas de plantas hospedeiras, provocando grandes perdas principalmente em solanáceas cultivadas em países de clima tropical e subtropical. Especificamente a raça 3 biovar 2 (R3B2) do patógeno, além de causar perdas diretas, causa infecções latentes em diversas hospedeiras, como o Pelargonium sp., o que facilita sua disseminação dentro e entre países. Por exemplo, na última década, esta bactéria foi introduzida nos EUA desta forma, causando preocupação em virtude da adaptação dessa variante à cultura da batata. Face à sua forte restrição quarentenária principalmente em países da América do Norte, onde adquiriu status de agente de bioterrorismo, avaliou-se a patogenicidade a gerânio de 36 isolados brasileiros, com ênfase na R3B2 de RS. Esses isolados foram avaliados quanto à sua capacidade de infectar gerânios (P. peltatum, P. hortorum), batata e tomate. Plantas jovens foram inoculadas pela penetração do xilema com um alfinete esterilizado contaminado pelo toque em colônia de RS de cada isolado. Foram usados 36 isolados, sendo 10 da biovar 1, 22 da biovar 2, dois da biovar 3 e dois de gerânio. A incidência da doença foi medida a cada dois dias pela porcentagem de plantas com sintomas da doença. Além do teste de patogenicidade a gerânio, os isolados foram identificados em filotipos com a finalidade de verificar se os isolados capazes de infectar estas hospedeiras se agrupavam de maneira a explicar alguns dos comportamentos. Todas as cinco cultivares de gerânio foram suscetíveis, porém ocorreram variações quanto à resposta entre isolados. Os gerânios, em geral, são menos suscetíveis a todos os isolados quando comparados com batata e tomate. Dezenove dos 36 isolados infectaram uma ou duas das espécies testadas e 17 infectaram ao menos uma planta de todas as espécies hospedeiras avaliadas. Isolados das raças 1 e 3, biovares 1, 2 e 3, filotipos I e II, foram capazes de infectar o gerânio. A capacidade de isolados brasileiros da R3B2 de RS de infectar o gerânio faz com que sejam necessários métodos especiais para identificação e detecção da bactéria em viveiros de plantas visando a exportação. Não foi possível agrupar os isolados segundo suas características patogênicas e moleculares; então, é proposto que análises de genoma completo sejam realizadas para que pequenos deste, possam revelar a gama de hospedeiras.