Due to the lack of a standardized visual method for assessing bacterial blight (Pseudomonas syringae pv. garcae) in coffee leaves, a diagrammatic scale was developed and validated to quantify the disease. Leaves were collected in crops and nursery with different intensity of symptoms, and the true severity was determined electronically. Based on the frequency distribution of severity values and according to the Weber-Fechner's law of visual stimulus, the minimum and maximum limits and the intermediate levels in the scale were determined. Validation was performed by ten evaluators who estimated the severity of 50 leaves with different intensity of symptoms. One evaluation was performed without diagrammatic scale and two evaluations with the scale at 7-day intervals. The accuracy, precision, repeatability and reproducibility of the estimates were evaluated. The scale had nine levels: 0 (0%), 1 (0.1-0.99%), 2 (1-2%), 3 (2.01-4%), 4 (4.01-8%), 5 (8.01-16%), 6 (16.01-25%), 7 (25.01-45%) and 8 (≥45.1%). Using the scale, the evaluators were able to improve accuracy, precision, reproducibility and repeatability of estimates, compared to evaluators without scale. The scale was appropriate to visual estimation of severity of bacterial blight in coffee leaves.

-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.Index terms: alternative control of plant disease, cell ultrastructure, pathogenic bacteria. Atividade antibacteriana de óleos essenciais sobre Xanthomonas vesicatoria e controle da mancha-bacteriana do tomateiroResumo -O objetivo deste trabalho foi avaliar o efeito de óleos essenciais (OEs) no crescimento de Xanthomonas vesicatoria, na morfologia e na ultraestrutura bacteriana, e na severidade da mancha-bacteriana do tomateiro. OEs de citronela, cravo-da-índia, canela, capim-limão, eucalipto, tomilho e árvore-de-chá foram avaliados in vitro nas concentrações de 0,1, 1,0, 10 e 100% em leite em pó a 1,0%. O efeito dos OEs, a 0,1%, na severidade da mancha-bacteriana do tomateiro foram avaliados em plantas de tomateiro em casa de vegetação. Os efeitos dos óleos de citronela, capim-limão, cravo-da-índia e árvore-de-chá, a 0,1%, nas células de X. vesicatoria foram avaliados por meio de microscopia eletrônica de transmissão. Todos os OEs apresentaram efeito tóxico direto sobre as bactérias na concentração de 10% in vitro. Em casa de vegetação, os OEs de cravo-da-índia, citronela, árvore-de-chá e capim-limão reduziram a severidade da doença. Os OEs de cravo-da-índia e árvore-de-chá, e o sulfato de estreptomicina promoveram perda de material eletro-denso e alterações no citoplasma, enquanto o OE de árvore-de-chá promoveu vacuolização do citoplasma, e os de citronela, capim-limão, cravo-da-índia e árvore-de-chá causaram danos à parede celular bacteriana. Os OEs, na concentração de 0,1%, reduzem a severidade da doença.Termos para indexação: controle alternativo de doenças de plantas, ultraestrutura celular, bactéria fitopatogênica.

No abstract

Foi investigada a eficácia comparativa da pulverização foliar em tomateiro de acibenzolar-S-metil (ASM) e Ecolife® na proteção contra Xanthomonas vesicatoria, bem como avaliada a ativação de algumas respostas bioquímicas de defesa de planta. Plantas de tomateiro cv. Santa Cruz Kada foram pulverizadas com acibenzolar S-metil (0,2 g l-1 ASM) e uma formulação natural proveniente de biomassa cítrica denominada Ecolife® (5 ml l-1). Quatro dias após as pulverizações, as plantas foram inoculadas com um isolado patogênico de Xanthomonas vesicatoria. Em experimentos de quantificação de doença, a pulverização foliar de Ecolife® e ASM conferiu 39,2% e 47,7% de proteção, respectivamente. A resistência induzida em plantas pulverizadas com ASM e Ecolife® foi evidenciada pelo aumento da atividade de peroxidases (POX) e oxidases de polifenóis (PPO), iniciado logo às primeiras horas após as pulverizações, continuando até 12 dias de avaliação. A despeito da tendência de queda nas atividades de amônia-liases de fenilalanina (PAL) a partir de 3 dias após as pulverizações, plantas tratadas com ASM e Ecolife® tiveram discreto aumento no acúmulo de lignina, principalmente aquelas pulverizadas com Ecolife® e inoculadas com X. vesicatoria. Teores de fenóis solúveis totais decresceram significativamente, 9 e 12 dias após pulverizações. O aumento nas atividades de POX e PPO poderia resultar em lignificação, a qual estaria associada a uma estratégia de defesa do tomateiro contra a mancha bacteriana.

No abstract

No abstract

RESUMOPara avaliar o potencial de 53 isolados de bactérias endofíticas no controle da pinta bacteriana do tomateiro (Lycopersicum esculentum Mill.), realizaram-se seleções massais em casa-de-vegetação e a seguir foi avaliado, in vitro, o antagonismo desses isolados sobre a bactéria desafiante Pseudomonas syringae pv. tomato (Pst). A inoculação das bactérias endofíticas foi feita por microbiolização das sementes de tomate cv. Santa Clara e da desafiante (Pst) por pulverização. Aos 7, 14 e 21 dias após a inoculação da Pst, foram realizadas as avaliações da severidade da pinta bacteriana, bem como da altura das plantas. As espécies e os isolados bacterianos mais eficazes na redução da severidade da pinta bacteriana foram: Acinetobacter johnsonii (isolado 10), Bacillus pumilus (isolados 3, 12, 20, 39, 51) Termos para indexação: Bactérias endofíticas, controle biológico, pinta bacteriana, tomate. ABSTRACTTo asses the potential of fifty three isolates of endophytic bacteria on the control of Pseudomonas syringae pv. tomato (Pst) in tomato (Lycopersicum esculentum Mill.), several screening were done in greenhouse followed by in vitro studies on antagonism of those isolates to Pst. The inoculation of endophytic bacteria was done by microbiolization of tomato cv Santa Clara seeds. The challenging bacterium (Pst) inoculation was done by spraying. At 7, 14 and 21 days after Pst inoculation the assessment of bacterial speck severity was done, and height of plants was also measured. The most efficient endophytic species and isolates in reducing disease severity were: Acinetobacter johnsonii (isolate 10), Bacillus pumilus (isolates, 3, 12, 20, 39, 51), Paenibacillus macerans (isolates, 37, 47), PIM 11, Bacillus sphaericus (isolate 45), B. amyloliquefaciens (isolate 50), TOM 2 , TOM 24 and Staphylococcus aureus (isolate 18). More than 50% of the endophytic isolates efficient in reducing disease severity belonged to Bacillus pumilus. From the most efficient endophytic species group, the species Bacillus pumilus and B. amyloliquefaciens inhibited the Pst growth in vitro. Several bacterial isolates promoted growth of tomato.

Black rot of crucifers, (Xanthomonas campestris pv. campestris) is the principal yield-limiting and destructive pathogen of cruciferous crop worldwide. In order to validate a bio-based control alternative for this disease, whey, lime sulfur, biofertilizer, Bordeaux mixture or raw milk were applied to kale (Brassica oleracea var. acephala) plants. The disease control was achieved by most of the tested products. Milk-based products (raw milk and whey) and biofertilizer reduced the severity by 44 and 56% in the field. Antioxidants, crude fibber, crude protein and lipid contents and kale yield were verified in the five treatments on the leaves with and without X. campestris pv. campestris inoculation. In the absence of the pathogen (non-inoculated), lime sulfur and Bordeaux mixture improved plant nutritional value compared to organic treatments, nevertheless milk-based products and biofertilizer improved the evaluated variables more than the control. However, on leaves inoculated with X. campestris pv. campestris raw milk increased antioxidant activity, crude protein and fiber contents, whereas biofertilizer increased kale yield, lipid and antioxidant contents. Milk-based products and biofertilizer were further evaluated in greenhouse trials to determinate the activity of defense-related enzymes and lignin content. Biofertilizer treatment resulted in increased phenylalanine ammonia lyase, catalase, peroxidase activities and lignin content. Hence, the application of milk-based products and biofertilizer are promising to control black rot of crucifers and also improves food quality by boosting nutritional values and antioxidant activity.