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URI permanente desta comunidadehttps://thoth.dti.ufv.br/handle/123456789/3352
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Item Exoenzymes as a pathogenicity factor for Colletotrichum gloeosporioides associated with coffee plants(Grupo Paulista de Fitopatologia, 2019) Armesto, Cecilia; Maia, Fernanda Gonçalves Martins; Monteiro, Fernando Pereira; Abreu, Mário Sobral dePhytopathogenic fungi during the penetration and colonization process are capable of secreting several enzymes, which enable infection of the host live tissue, acting on the degradation of wax, cuticle and cell walls. The ability of a pathogenic agent to produce enzymes or not can determine the severity degree of a disease. In this study, 33 isolates of Colletotrichum gloeosporioides related to anthracnose and blister spot on coffee trees were evaluated for their ability to produce hydrolytic enzymes (amylase, lipase, protease, laccase, pectinase and cellulase) and specific cell wall degrading enzymes “CWDEs” (polygalacturonase, polymethylgalacturonase and pectin-lyase), as well as their relationship with the pathogenicity/aggressiveness of isolates. For all isolates of C. gloeosporioides, extracellular enzymes could be detected, except cellulases. Isolates I-9 and I-24 produced the highest levels of extracellular enzymes, as well as CWDEs. They also had the highest disease intensity indexes, suggesting a relationship between enzymes and aggressiveness of the isolates.Item GFP-fluorescent protein on the study of blister spot in coffee plants(Grupo Paulista de Fitopatologia, 2015) Armesto, Cecilia; Martins-Maia, Fernanda Gonçalves; Monteiro, Fernando Pereira; Abreu, Mário Sobral deColletotrichum gloeosporioides no Brasil está associado a um complexo de sintomas na cultura do café. Apesar da observação e da identificação da patogenicidade deste, o patógeno ainda tem sua importância questionada, devido às várias formas endofíticas do mesmo, levantando dúvidas sobre a real importância do patossistema. O presente trabalho teve como objetivo demonstrar por meio da utilização de um isolado transformado com o gene gfp a capacidade de infecção e colonização de C. gloeosporioides em plântulas de café. Pode-se observar após o quarto dia da inoculação a exteriorização de sintomas como necrose pontuais as quais progrediram durante o período de avaliação, culminando na morte das plântulas. Por meio de microscopia de epifluorescencia pode-se confirmar a presença do patógeno nas plântulas, assim como visualizar a colonização interna do tecido, a formação de acérvulos e produção de conídios, confirmando que o mesmo foi o responsável pelos sintomas observados.Item Colletotrichum on coffee trees in south of Minas Gerais - Brazil: physiological, molecular and pathogenic description(Editora UFLA, 2016-10) Armesto, Cecilia; Maia, Fernanda Gonçalves Martins; Monteiro, Fernando Pereira; Abreu, Mário Sobral deFungi of the genus Colletotrichum spp. are cosmopolitan and are responsible for disease in many plants of agronomic importance. In coffee crops, three species have been described: Colletotrichum acutatum, Colletotrichum kahawae and Colletotrichum gloeosporioides. In Brazil were only reported the species C. acutatum and C. gloeosporioides, which symptoms are attributed as antracnoses, dieback and blister spot. This study evaluates the population of Colletotrichum spp. through morpho-physiological, genetic and pathogenic characteristics, in several coffee plantations in the southern of Minas Gerais. All isolates showed similar morphological and physiological characteristics, being identified as C. gloeosporioides. The best medium for mycelial growth was agar-malt extract with pH 5.5 and for spore production oat-agar medium with pH 6.5. When inoculated on berries, all isolates were pathogenic with variable levels of aggressiveness, but only 57% of these were pathogenic for hypocotyls. Three isolates, I-9, I-24 and I-26, were identified featuring the highest rates of aggressiveness in berries and hypocotyls.Item Effect of light and temperature on Cercospora coffeicola and Coffea arabica pathosystem(Editora UFLA, 2016-04) Silva, Marília Goulart da; Pozza, Edson Ampélio; Monteiro, Fernando Pereira; Lima, Caio Vítor Rodrigues Vaz deThe mycelial growth rate (MGR), in vitro production of cercosporin, and intensity (incidence and severity) of Cercospora leaf spot on coffee seedlings ‘Catuaí Vermelho IAC 144’ were evaluated under different light intensities (80, 160, 240, and 320 μmol m -2 s -1 ) and temperatures (17, 21, 25, and 29°C). Dark condition (0 μmol m -2 s -1 ) was also included in in vitro experiments. In vivo, were evaluated incidence, severity, rates of chlorophyll a, b, and total in healthy (without symptoms) and sick tissues (with symptoms), and the photosynthetic rate and variables affecting it, were also evaluated. All the experiments were done at least two times. In in vitro experiments, the highest mycelial growth rate (MGR) was observed at 24.1°C in the dark condition (0 μmol m -2 s -1 ), while the highest amount of toxin occurred at 24.9°C and light intensity 320 μmol m -2 s -1 . When dishes were incubated in the dark, the lowest levels of cercosporin were produced by the pathogen, regardless of temperature, thus confirming the importance of light in the activation of toxin production. In in vivo experiments, the highest incidence and severity progress of the disease were observed at 21°C. With respect to the amounts of chlorophyll a, b, and total, regardless of treatment, the lowest levels were found in the area of the leaf with symptons compared to the area without symptoms. Photosynthesis correlated positively with temperature and negatively with internal carbon. These results elucidate the effect of the interaction between temperature and light intensity, contributing to future studies with this pathosystem.Item Progresso da cercosporiose do cafeeiro sob diferentes manejos de irrigação e densidades de plantio(Editora UFLA, 2013-04) Paiva, Bernardo Reis Teixeira Lacerda; Souza, Paulo Estevão de; Scalco, Myriane Stella; Monteiro, Fernando PereiraA irrigação assim como o adensamento são práticas que alteram o microclima da cultura, as quais interferem na luminosidade, na temperatura e na umidade relativa do ar e, por consequência, na intensidade de doenças no cafeeiro. Por isso, quantificar a influência dessas práticas no progresso das doenças torna-se útil na tomada de decisão sobre o seu manejo adequado. Avaliou-se, no presente trabalho, o efeito de diferentes densidades de plantio e manejos de irrigação na incidência e na severidade da cercosporiose em cafeeiros adultos e relacionaram-se manejos de irrigação e densidades de plantio ao progresso da doença e enfolhamento da planta. O delineamento experimental foi em blocos ao acaso, com quatro repetições, em esquema de parcelas subdivididas. Os tratamentos foram constituídos por quatro densidades de plantio localizadas nas parcelas: 2.500 (4,0 x 1,0m), 3.333 (3,0 x 1,0m), 5.000 (2,0 x 1,0m) e 10.000 (2,0 x 0,5m) plantas.ha -1 e quatro manejos de irrigação (subparcelas), sendo: irrigação quando a tensão da água no solo atingiu valores próximos a 20kPa; irrigação quando a tensão da água no solo atingiu valores próximos a 60kPa; irrigação com a utilização de manejo do balanço hídrico climatológico (calculado por meio do software Irriplus) e uma testemunha não irrigada. Cada linha da subparcela foi constituída por 10 plantas, sendo consideradas como plantas úteis as seis centrais. Verificou-se que os manejos de irrigação influenciaram a incidência da cercosporiose e o enfolhamento, sendo que, em plantas não irrigadas a incidência da cercosporiose foi 30% maior, que os manejos irrigados. Quanto ao enfolhamento verificou-se que os tratamentos 20kPA e 60 kPA foram 9% e 5% maior comparado ao tratamento não irrigado. O aumento mais expressivo no enfolhamento foi obtido quando empregado o manejo do balanço hídrico com um valor 13% maior que a testemunha. Na análise de regressão da área abaixo da curva do progresso da severidade e incidência, o modelo quadrático obteve o melhor ajuste, tendo as equações y=0,000004x 2 -0,0137x+192,05 (R 2 =0,6901) e y=0,000014x 2 -0,4048x+5943,7 (R 2 =0,6086), respectivamente. O valor de mínima para área abaixo da curva do progresso da severidade foi obtido quando utilizada uma densidade de 7500 plantas por hectare aproximadamente. O valor de máxima foi obtido quando empregada a densidade de 1712,5 plantas por hectare. Para a área abaixo da curva do progresso da incidência foram obtidos resultados semelhantes. Os sistemas de plantios adensados, 10.000 plantas/ha e 5.000 plantas/ha, reduziram a incidência da cercosporiose em 35% e 31,5%, respectivamente. As densidades de plantio não interferiram no enfolhamento.Item Progress of cercospora leaf spot in coffee under different irrigation management systems and planting densities(Editora UFLA, 2013-04) Paiva, Bernardo Reis Teixeira Lacerda; Souza, Paulo Estevão de; Scalco, Myriane Stella; Monteiro, Fernando PereiraIrrigation and density are practices that change the microclimate of the crop and affect the incidence of light, temperature and relative humidity and, thus, the intensity of diseases in coffee. Therefore, quantifying the influence of these practices on disease progress is useful in making decisions regarding their appropriate management. This study evaluated the effect of different planting densities and irrigation management practices on the incidence and severity of Cercospora leaf spot on adult coffee plants, and irrigation and planting density practices were related to progress of the disease and plant leaf development. A randomized block experimental design was used with four replications in a split-plot arrangement. The treatments consisted of four planting densities located in the plots (conventional and dense): 2500 (4.0 x 1.0 m), 3333 (3.0 x 1.0 m), 5000 (2.0 x 1.0 m) and 10,000 (2.0 x 0.5 m) plants.ha -1 , and four irrigation management practices (split-plots), which were: irrigation when soil water tension reached values near 20kPa; irrigation when soil water tension reached values near 60 kPa; irrigation management using the climatic water balance (calculated by the software Irriplus); and a control without irrigation. Each row in the split-plot consisted of 10 plants, with the six center plants being considered as useful. It was found that irrigation management influences the incidence of Cercospora leaf spot and leaf formation; in non-irrigated plants the incidence of Cercospora leaf spot was 30% greater than in the irrigated managements. The foliage had values close to 1000 as the area under the disease progress curve. In regression analysis of the area under the severity and incidence progress curve, the quadratic model gave the best fit, with the following equations: y=0.000004x 2 -0.0137x+192.05 (R 2 =0.6901) and y=0.000014x2-0.4048x+5943.7 (R 2 =0.6086), respectively. The minimum value of the area under the severity progress curve was obtained when using a density of approximately 7500 plants per hectare. The maximum value was obtained when using the density of 1712.5 plants per hectare. For the area under the incidence progress curve, similar results were obtained. High planting density systems of 10,000 plants/ha and 5,000 plants/ha reduced the incidence of Cercospora leaf spot by 35% and 31.5%, respectively. Planting density did not affect leaf development.