Antibacterial activity of essential oils on Xanthomonas vesicatoria and control of bacterial spot in tomato

The objective of this work was to evaluate the effects of plant essential oils (EOs) on the growth of Xanthomonas vesicatoria, on bacterial morphology and ultrastructure, and on the severity of tomato bacterial spot. EOs from citronella, clove, cinnamon, lemongrass, eucalyptus, thyme, and tea tree were evaluated in vitro at concentrations of 0.1, 1.0, 10, and 100% in 1.0% powdered milk. The effect of EOs, at 0.1%, on the severity of tomato bacterial spot was evaluated in tomato seedlings under greenhouse conditions. The effects of citronella, lemongrass, clove, and tea tree EOs, at 0.1%, on X. vesicatoria cells were evaluated by transmission electron microscopy. All EOs showed direct toxic effect on the bacteria at a 10%‑concentration in vitro. Under greenhouse conditions, the EOs of clove, citronella, tea tree, and lemongrass reduced disease severity. EOs of clove and tea tree, and streptomycin sulfate promoted loss of electron‑dense material and alterations in the cytoplasm, whereas EO of tea tree promoted cytoplasm vacuolation, and those of citronella, lemongrass, clove, and tea tree caused damage to the bacterial cell wall. The EOs at a concentration of 0.1% reduce the severity of the disease.The objective of this work was to evaluate the effects of plant essential oils (EOs) on the growth of Xanthomonas vesicatoria, on bacterial morphology and ultrastructure, and on the severity of tomato bacterial spot. EOs from citronella, clove, cinnamon, lemongrass, eucalyptus, thyme, and tea tree were evaluated in vitro at concentrations of 0.1, 1.0, 10, and 100% in 1.0% powdered milk. The effect of EOs, at 0.1%, on the severity of tomato bacterial spot was evaluated in tomato seedlings under greenhouse conditions. The effects of citronella, lemongrass, clove, and tea tree EOs, at 0.1%, on X. vesicatoria cells were evaluated by transmission electron microscopy. All EOs showed direct toxic effect on the bacteria at a 10%‑concentration in vitro. Under greenhouse conditions, the EOs of clove, citronella, tea tree, and lemongrass reduced disease severity. EOs of clove and tea tree, and streptomycin sulfate promoted loss of electron‑dense material and alterations in the cytoplasm, whereas EO of tea tree promoted cytoplasm vacuolation, and those of citronella, lemongrass, clove, and tea tree caused damage to the bacterial cell wall. The EOs at a concentration of 0.1% reduce the severity of the disease

Isolamento e Caracterização de Bactérias do Lodo de Esgoto com Potencial Antagonismo a NematóidesIsolation and Characterization of Bacteria from Sewage Sludge, with Potential Antagonism to Nematodes

Foram isoladas e caracterizadas bactérias presentes no lodo de esgoto visando à realização de estudos futuros de interação desses organismos com fi tonematóides. Os lodos utilizados são provenientes das estações de tratamento de Franca e Barueri, no Estado de São Paulo. Foram obtidos 77 isolados do lodo de Franca e 143 do de Barueri. Desses isolados de Franca testados, 77% foram Gram-positivos e 23% Gram-negativos. Para os 143 isolados obtidos do lodo de esgoto de Barueri, 61% foram Gram-positivos e o restante Gram-negativo. Os isolados Gram-positivos podem, estar relacionados com espécies do gênero Bacillus dos quais várias espécies têm grande importância como agentes de controle de fi topatógenos, inclusive nematóides. Observou-se que 39% e 40% dos microrganismos Gram positivos, isolados dos lodos coletados na ETE de Franca e de Barueri, produziram pigmento fluorescente em meio King B, sendo indicativo de Pseudomonas fluorescens. Dos 77 isolados de Franca, 13% apresentaram como característica morfológica bordo lobado, característica de culturas de Bacillus. Comparando-os com os testes bioquímicos, concluiu-se que 80% deles foram Grampositivos, característica de espécies de Bacillus. Dos isolados, 10% apresentaram bordo inteiro, colônia brilhante e arredondada, as quais são características de Pseudomonas. Desses, 37% foram Gram-negativos, sendo que 67% desses isolados eram também produtores de pigmento fluorescente em meio King B, características da P. fluorescens. Dos 143 isolados de Barueri, 17% apresentaram bordo lobado como característica morfológica, podendo-se suspeitar de serem espécies de Bacillus e 5% apresentaram as características de espécies de Pseudomonas. Para os isolados do lodo de Barueri, na comparação com os testes bioquímicos constatou-se que 64% dos isolados foram Gram-positivo. Dos isolados com características de Pseudomonas, 17% apresentaram-se como Gramnegativas e desses, 17% mostraram-se como produtores de pigmento fluorescente em meio King B, que são características de espécies de Pseudomonas do grupo fluorescente.Summary This work aimed at isolating and characterizing bacteria presented in sewage sludge with the objective of future studies for the interaction of these organisms with nematodes. For this study, it was used samples of the sewage sludge originated from the treatment stations of the cities of Franca and Barueri, in the state of São Paulo. It was obtained 77 samples of isolated sewage sludge from Franca and 143 from Barueri. From the Franca samples, 77% was Gram-positive and 23% was Gram-negative while from the Barueri samples, 61% was Gram-positive and the rest was Gram-negative. The isolated Gram-positive can be related to the species of the genre Bacillus, whose species have great importance as agents of the phytopathogens control, including nematodes. It was observed that 39% and 40% of the Gram-positive microorganisms isolated from the collected sewage sludge in ETE from Franca and from Barueri produced fluorescent pigments in King B medium, as indicative of Pseudomonas fluorescent presence. By examining the 77 samples of sewage sludge from Franca, 13% presented as morphologic characteristic, the margin of lobes, characteristic of the Bacillus culture. When compared them to the biochemistry tests, it was concluded that 80% was Gram-positive, a characteristic of the Bacillus species. By isolating the samples of sewage sludge from Franca, 10% presented whole margin, fluorescent and round colony, characteristics of the Pseudomonas while 37% was Gram-negative, considering that 67% of this isolated sewage sludge produced fluorescent pigments in King B medium, characteristics of Pseudomonas fluorescence. By examining the 143 samples of sewage sludge from Barueri, 17% presented the margin of lobes, as a morphologic characteristic, suggesting that they belonged to the Bacillus species and 5% presented the characteristic of the Pseudomonas species. By isolating the samples of sewage sludge from Barueri, it was found out, during the comparison with the biochemistry tests, that 64% was Gram-positive. From the isolated sewage sludge that presented the Pseudomonas characteristics, 17% indicated to be Gram-negative while 17% demonstrated to be producers of fl uorescent pigments in King B medium, characteristics of the Pseudomonas species from the fluorescent group

Antibacterial activity of essential oils on Xanthomonas vesicatoria and control of bacterial spot in tomato

The objective of this work was to evaluate the effects of plant essential oils (EOs) on the growth of Xanthomonas vesicatoria, on bacterial morphology and ultrastructure, and on the severity of tomato bacterial spot. EOs from citronella, clove, cinnamon, lemongrass, eucalyptus, thyme, and tea tree were evaluated in vitro at concentrations of 0.1, 1.0, 10, and 100% in 1.0% powdered milk. The effect of EOs, at 0.1%, on the severity of tomato bacterial spot was evaluated in tomato seedlings under greenhouse conditions. The effects of citronella, lemongrass, clove, and tea tree EOs, at 0.1%, on X. vesicatoria cells were evaluated by transmission electron microscopy. All EOs showed direct toxic effect on the bacteria at a 10%-concentration in vitro. Under greenhouse conditions, the EOs of clove, citronella, tea tree, and lemongrass reduced disease severity. EOs of clove and tea tree, and streptomycin sulfate promoted loss of electron-dense material and alterations in the cytoplasm, whereas EO of tea tree promoted cytoplasm vacuolation, and those of citronella, lemongrass, clove, and tea tree caused damage to the bacterial cell wall. The EOs at a concentration of 0.1% reduce the severity of the disease

Bactérias endofíticas como agentes promotores do crescimento de plantas de tomateiro e de inibição in vitro de Ralstonia solanacearum Endophytic bacteria as agents of plant growth promotion in tomato and inhibition in vitro of Ralstonia solanacearum

A partir de 150 isolados de bactérias endofíticas obtidos de folhas, caules e raízes de tomateiros sadios, 53 destacaram-se quanto à habilidade em promover o crescimento de plantas de tomateiro (Solanum lycopersicum L.). Submetidos a uma nova seleção, os isolados UFV-E17, UFV-E22, UFV-E25, UFV-E26, UFV-E27, Bacillus cereus (UFV-E29), UFV-E49, UFLA 06-LS, UFLA 08-LS e UFLA 11-LS apresentaram maior promoção do crescimento. Avaliações semanais de altura e número de folhas e folíolos das plantas aconteceram durante 45 dias. Após a sexta avaliação, mensurou-se a área foliar e o peso da matéria fresca e seca da parte aérea e da raiz das plantas. O isolado UFV-E49 apresentou melhor resultado para altura, área foliar, número de folhas e peso da matéria fresca e seca, tanto da parte aérea quanto da raiz. Dos isolados selecionados, somente dois apresentaram efeito inibitório direto in vitro a Ralstonia solanacearum.<br>Out of one hundred and fifty isolates of endophytic bacteria from leaves, stems and roots of healthy tomatoes (Solanum lycopersicum L.), fifty three showed ability to promote tomato plant growth, among these, ten isolates UFV-E17, UFV-E22, UFV-E25, UFV-E26, UFV-E27, Bacillus cereus (UFV-E29), UFV-E49, UFLA 06-LS, UFLA 08-LS and UFLA 11-LS, provided the largest plant growth promotion. Weekly assessment of plant height and number of leaves and leaflets were carried out during 45 days. After the sixth evaluation, the leaf area and the fresh and dry weight of the aerial part of plants and of the roots were measured. Isolate UFV-E49 provided the largest values of height, leaf area, number of leaves and fresh and dry weight of the aerial part of plants as well as the root. From the selected isolates, only two presented antimicrobial activity against Ralstonia solanacearum

Levantamento de doenças em plantas ornamentais diagnosticadas na Clínica Fitossanitária da Universidade Federal de Lavras, Lavras/MG, no período de 2002 a 2006

O objetivo deste trabalho foi verificar os resultados de amostras de análises realizadas na Clínica Fitossanitária com plantas ornamentais, considerando espécie, região, patógeno diagnosticado e freqüência de ocorrência, no período de 2002 a 2006.

Aumento da eficiência nutricional de tomateiros inoculados com bactérias endofíticas promotoras de crescimento

Bactérias endofíticas promotoras de crescimento podem aumentar a eficiência nutricional das plantas, favorecendo sua produção. O objetivo deste trabalho foi avaliar a influência de 10 isolados de bactérias endofíticas, previamente selecionados como agentes promotores do crescimento de plantas, sobre a eficiência de absorção, utilização e translocação de nutrientes em plantas de tomateiros em casa de vegetação. Para a introdução das bactérias endofíticas em plântulas de tomateiro cv. Santa Clara, utilizou-se o corte do hipocótilo. Cinqüenta e cinco dias após o transplantio das seções de parte área, as plantas foram coletadas para a determinação da matéria seca da parte aérea e dos teores de macro e micronutrientes. Os teores de N, P, K, Ca, Mg, Cu e Zn na parte aérea e os de N, P, Mg e Mn nas raízes das plantas inoculadas diferiram da testemunha sem inoculação. As bactérias endofíticas Micrococcus sp. (UFLA 11-LS) e Brevundimonas sp. (UFV-E49), identificadas por meio do seqüenciamento do gene 16S do DNA ribossômico, propiciaram a maior eficiência de absorção de P em relação à testemunha. A bactéria endofítica Micrococcus sp. apresentou maior eficiência na utilização de N, P, K, Ca, Mg, S, Cu, Fe e Zn. Os maiores teores de N, P, K, Mg e Zn foram encontrados na parte aérea das plantas inoculadas com Brevundimonas sp. Os resultados deste trabalho indicam que estes isolados de bactérias endofíticas podem aumentar a eficiência nutricional de plantas de tomate

Induced defense responses in tomato against bacterial spot by proteins synthesized by endophytic bacteria

Some endophytes can synthesize molecules that elicit the induction of plant resistance to infection by pathogens. The objective of this study was to demonstrate that protein fractions 42 and 75 from Bacillus amyloliquefaciens and Bacillus pumilus were capable of acting as elicitors of induced resistance in tomato plants against Xanthomonas vesicatoria, following partial resolution by gel-filtration chromatography. Tomato plants sprayed with protein fractions 42 and 75 reduced, respectively, 63.5 and 56.6% of bacterial spot, compared with control plants. Additionally, these fractions promoted the increase of peroxidase (POX) and polyphenol oxidase (PPO) enzyme activities in treated plants. In SDS-PAGE stained with silver nitrate, protein fractions 42 and 75 appeared as simple bands with estimated molecular mass of 28 and 43 kDa, respectively. We report the partial characterization of two macromolecules synthesized by endophytic bacteria that act as elicitors of systemic resistance in tomato against X. vesicatoria