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.

RESUMOSubmitted on 07/20/2014 and aproved on 11/30/2014. 1 Universidade Federal de Lavras, Departamento de Fitopatologia, Lavras, Minas Gerais, Brasil. edsonpozza@gmail.com; deilamagna@hotmail.com 2 Universidade Federal de Lavras, Departamento de Ciência do Solo, Lavras, Minas Gerais, Brasil. adelia.pozza@dcs.ufla.br *Autor para correspondência: edsonpozza@gmail.com Revisão de Literatura Silicon in plant disease controlAll essential nutrients can affect the incidence and severity of plant diseases. Although silicon (Si) is not considered as an essential nutrient for plants, it stands out for its potential to decrease disease intensity in many crops. The mechanism of Si action in plant resistance is still unclear. Si deposition in plant cell walls raised the hypothesis of a possible physical barrier to pathogen penetration. However, the increased activity of phenolic compounds, polyphenol oxidases and peroxidases in plants treated with Si demonstrates the involvement of this element in the induction of plant defense responses. The studies examined in this review address the role of Si in disease control and the possible mechanisms involved in the mode of Si action in disease resistance in plants.Key words: Management, plant diseases, resistance barriers, soil fertility, resistyance inducers. O Silício no controle de doenças de plantasTodos os nutrientes essenciais podem influenciar a incidência e a severidade das doenças de plantas. O silício (Si), embora não seja considerado nutriente essencial para plantas, destaca-se por seu potencial para diminuir a intensidade de doenças em várias culturas. O mecanismo de ação do Si na resistência de plantas ainda não está totalmente esclarecido. A forma de deposição do Si na parede celular de plantas gerou a hipótese de uma possível barreira física, dificultando a penetração do patógeno. No entanto, o aumento da atividade de compostos fenólicos, polifenoloxidases e peroxidases em plantas tratadas com Si demonstra o envolvimento deste elemento na indução de reações de defesa da planta. A presente revisão visa abordar o papel do Si no controle de doenças e os possíveis mecanismos envolvidos no modo de ação do Si na resistência de plantas às doenças.Palavras-chave: Manejo, doenças de plantas, barreiras de resistência, fertilidade do solo, indutores de resistência. 324Edson Ampélio Pozza et al.

do silício no controle da cercosporiose em três variedades de cafeeiro. Fitopatologia Brasileira 29: 185-188. 2004. RESUMOA cercosporiose do cafeeiro (Coffea arabica), causada por Cercospora coffeicola, é uma das mais importantes doenças na fase de viveiro. O objetivo desse trabalho foi avaliar o efeito da aplicação de silício (1 g de CaSiO 3 incorporada em 1 kg do substrato utilizado para encher os tubetes) no controle dessa doença em três variedades de cafeeiro (catuaí, mundo novo e icatú) e, determinar quais os possíveis fatores de resistência associados. As plantas com dois pares de folhas foram inoculadas com suspensão de 1,4 x 10 4 conídios de C. coffeicola por ml. Aos sete meses após a inoculação avaliaram-se a porcentagem de folhas lesionadas e o número total de lesões por planta. Após essa avaliação, retiraram-se amostras das folhas para o estudo em Microscopia Eletrônica de Varredura (MEV) e Microanálise de Raios-X (MAX). As plantas da variedade catuaí tratadas com silicato, tiveram redução de 63,2% nas folhas lesionadas e de 43% no total de lesões por planta, em relação à testemunha. A MAX e o mapeamento para Si indicaram distribuição uniforme do elemento em toda a superfície abaxial das folhas de cafeeiro nas três variedades tratadas. Nas folhas das plantas não tratadas, o Si foi raramente encontrado. Nas imagens de MEV também foi observada camada de cera bem desenvolvida na superfície inferior das folhas originárias de todas as plantas tratadas, sendo esta mais espessa em catuaí e rara ou ausente nas não tratadas.Palavras-chave adicionais: mancha de olho pardo, Coffea arabica, Cercospora coffeicola, nutrição mineral. ABSTRACT Effect of silicon on the control of brown eye spot in three coffee cultivarsBrown eye spot of coffee (Coffea arabica) is an important nursery disease. The goal of this work was to evaluate the effect of silicon (1 g of CaSiO 3 incorporated in 1 kg of substrate used to fill the containers) on the control of this disease in three coffee cultivars, catuaí, mundo novo and icatú, and to determine which resistance factors were stimulated. Young plants with two pairs of leaves were inoculated with a suspension containing 1.4 x 10 4 Cercospora coffeicola conidia.ml -1 . Seven months after inoculation the plants were evaluated to determine the percentage of leaves with disease (%) and the total number of lesions per plant. Before the evaluation, leaf samples were studied using a scanning electron microscope and X-ray microanalysis. In the catuaí cultivar treated with silicon, ther was a reduction of 63,2% of leaves with lesions and 43% of total lesions per plant, in relationship the non-treated plants. X-ray microanalysis and mapping of Si showed uniform distribution of elements on all abaxial surfaces of leaves in all the treated cultivars. On leaves of non-treated plants, the Si was rare or absent. Scanning electron microscopy also showed a very well developed wax layer on the lower leaf surfaces of all cultivars, but this layer was thicker in the catuaí cultivar and thin or absent in ...

INOCULATION OF BEAN SEEDS WITH Fusarium oxysporum f. sp. phaseoli THROUGH WATER RESTRICTION TECHNIQUEABSTRACT -The objective of the present work was to test methodology of inoculation of bean seeds with Fusarium oxysporum f. sp. phaseoli using water restriction technique. For that, three solutes, sucrose, potassium chloride and manitol, added to the medium potato-sucrose-agar, PSA at three water potentials (-0.8, -1.0, -1.2 MPa) and four duration periods of the exposition of seeds to the fungus (36, 72, 108 and 144h) were used. The effects of the fungus on the performance of the seeds and emerged plants were evaluated looking at germination and health ( blotter-test). The mycelial growth of the fungus in vitro, was not reduced by any osmotic treatment. Higher growth of the fungus was observed at osmotic potentials of -0.8 e -1.0 MPa. At longer durations of exposition of the seeds to the pathogen, 108 e 144h, mycelial growth of the fungus was higher and affected seed performance. The greatest mean incidence of Fusarium oxysporum f. sp. phaseoli (64%) was detected on seeds in wich KCl was used. At 144h of inoculation period on that solute, the incidence was of 70%.

Resumo -Objetivando avaliar a intensidade da mancha-de-olho-pardo do cafeeiro, variedade Catuaí Vermelho, com relação ao estado nutricional das plantas quanto a N e K, realizou-se um experimento no viveiro da Universidade Federal de Viçosa, em Viçosa, MG, utilizando solução nutritiva circulante. Empregaram-se 16 tratamentos, em delineamento inteiramente casualizado, com três repetições e duas plantas por parcela, em esquema fatorial com quatro doses de K (3, 5, 7 e 9 mmol/L) e quatro doses de N (3, 7, 11 e 15 mmol/L). Após sete inoculações de conídios, e avaliações, colheram-se as plantas. A produção de matéria seca total, a área foliar total, e a área abaixo da curva de progresso (AACP) do número total de folhas não foram influenciadas pelas doses de K, mas aumentaram com o incremento das doses de N. Observou-se elevação, na AACP, do número de lesões por folha, e na desfolha com o aumento das doses de K e a redução das doses de N. A elevação nas doses de K promoveu redução nos teores foliares de Ca e Cu. Os teores foliares de P, Mg, Mn e Fe não foram influenciados pelas doses de K e tiveram pequena redução com o aumento de N na solução, elevando-se a seguir.Termos para indexação: Coffea arabica, nutrição das plantas, nutrientes minerais, Cercospora coffeicola, doenças das plantas. Influence of the mineral nutrition on intensity of brown-eye spot in young coffee plantsAbstract -The experiment was carried out at the coffee nursery of the Universide Federal de Viçosa, in Viçosa, MG, Brazil, using nutrient circulating solution to evaluate the intensity of brown-eye spot (Cercospora coffeicola), variety Catuaí Vermelho, as a function of N and K. A completely randomized design with 16 treatments, three replicates, and two plants per plot was used in a factorial with four levels of K (3, 5, 7 and 9 mmol/L) combined with four levels of N (3, 7, 11 and 15 mmol/L). After seven inoculations and evaluations, the plants were picked. Total dry matter production, total leaf area, and the area below the curve of progress (AACP) for the total number of leaves were not influenced by the levels of K, but increased with increasing levels of N. There was increase in AACP areas for the number of lesions per leaf and defoliation, with the increase of K levels, and a reduction of N levels. The increase in K levels reduced the Ca and Cu leaf contents, indicating possible relation between its contents and the increase of the disease. The P, Mg, Mn, and Fe leaf contents were not influenced by the K levels, and had a small reduction with increased N contents in the nutrient solution, increasing thereafter.

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RESUMOForam realizados três experimentos para estudar a influência do silício na redução da antracnose, causada por Colletotrichum lindemuthianum, em feijoeiro (Phaseolum vulgaris). No primeiro experimento plantas tratadas com silicato de cálcio foram inoculadas com 0, 10 3 , 10 4 , 5x10 4 , 10 5 , 5x10 5 e 10 6 conídios/ml de C. lindemuthianum. Na concentração de 10 6 conídios/ml avaliou-se a diferença entre o silicato de cálcio e uma fonte de cálcio (óxido de cálcio). No segundo experimento foi avaliado o silicato de cálcio e de sódio na redução da antracnose. No terceiro experimento, por meio da microscopia eletrônica de varredura (MEV) e da microanálise de raios-X (MAX), estudou-se o efeito do silício nos mecanismos de resistência. Foram realizadas cinco avaliações da doença, utilizadas para calcular a área abaixo da curva de progresso da incidência (AACPI), da severidade (AACPS) e a duração da área foliar sadia (HAD), nos dois primeiros experimentos. Com o aumento da concentração do inóculo houve aumento na AACPI e AACPS e redução na HAD, porém a testemunha inoculada com a maior concentração de inóculo, e tratada apenas com cálcio (CaO), sem silicato, teve maiores AACPI e AACPS do que as plantas tratadas com silicato de cálcio. No segundo experimento, a menor AACPS e maior HAD foram obtidas no tratamento com silicato de sódio via foliar, que proporcionou redução de 62,4% na AACPS. Na MEV e na microanálise de raios X não se observaram a formação de barreira física e o acúmulo de silício externamente com a aplicação de silicato de cálcio, embora o elemento tenha contribuído para reduzir a antracnose.Palavras-chave adicionais: Colletotrichum lindemuthianum, nutrição mineral, concentração de inóculo, Phaseolus vulgaris. ABSTRACTEffects of silicon sources on the incidence and severity of the common beans anthracnose Three experiments were performed to study the influence of the silicon on the reduction of the common bean (Phaseolum vulgaris) anthracnose. The first experiment involved a plant fertilized with calcium silicate and different inoculum concentrations of the Colletotrichum lindemuthianum (0, 10 3 , 10 4 , 5x10 4 , 10 5 , 5x10 5 and 10 6 conidia/ml). In the concentration 10 6 conidia/ml the difference between calcium silicate and calcium oxide was evaluated for effects on the disease. The second experiment evaluated the influence of sodium and calcium silicate on the reduction of the anthracnose. In the third experiment, the scanning electron microscopy (SEM) and X-ray micro-analysis (EDAX) were used to study the effect of the silicon on the plant resistance mechanism. Five evaluations of the incidence, severity and leaf area were done, in the first and second experiment. Disease evaluation was made using area under disease progress curve for incidence (AUDPCI) and severity (AUDPCS) and healthy leaf area duration (HAD). Inoculum concentration was found to increase the AUDPCI and AUDPCS. In contrast, the HAD had decreased. Fertilization of plants with calcium silicate significantly reduced the AUDPCI and...

0.85) for all variables, except for plant height which presented correlation coefficient of 0.77. The most severe effect of the fungus in this study occurred on the root system of the emerged plants as determined by the highest inoculum intensity of the pathogen on the planted seeds.]]>