Navegando por Autor "Maia, Fernanda Gonçalves Martins"

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Colletotrichum gloeosporioides : transmissibilidade em sementes e mecanismos de defesa de mudas micropropagadas de cafeeiro (Coffea arabica L.)
(Universidade Federal de Lavras, 2011-11-04) Maia, Fernanda Gonçalves Martins; Abreu, Mário Sobral de
No complexo Colletotrichum x cafeeiro, poucos são os estudos no que se referem transmissibilidade do patógeno em plantas infectadas e aos mecanismos de defesa o que dificulta a elucidação de aspectos importantes da doença na cultura. Neste contexto, o presente trabalho foi realizado com o objetivo de acompanhar via microscopia de epifluorescência, a de transmissibilidade do patógeno semente-plântulas, os efeitos da presença do patógeno na semente sobre parâmetros de qualidade destas e os mecanismos de defesa que cafeeiros utilizam em reação a presença do patógeno e dessa maneira esclarecer pontos importantes do patossistema Colletotrichum x cafeeiro. O efeito de C. gloeosporioides na germinação, na viabilidade da semente e no estabelecimento de plântulas foi realizado com um isolado não transformado (I2) e um transformado pela técnica da GFP (I2-T) inoculados em sementes da cultivar Catuaí Vermelho (sementes de plantas com (PCS) e sem (PSS) sintomas de mancha-manteigosa) submetidas por diferentes potenciais de inóculo ( P0 – P5), pelo contato direto com a colônia em placas de Petri. Foram consideradas as variáveis, sanidade, germinação, índice de velocidade de emergência, tetrazólio e transmissibilidade. Verificou-se que, com o aumento do potencial de inóculo, houve aumento da incidência nas sementes para os dois materiais estudados. A porcentagem máxima de infecção nas sementes foi de 6% para PSS (I2) e 26,66% para PCS (I2-T). Em relação à variável germinação, só foi possível observar interação significativa (p<0,05) entre material genético x potencial de inóculo. Pelo teste do IVE ficou evidenciado que houve decréscimo de vigor, à medida que se aumentou o potencial de inóculo em ambos os materiais estudados. Em relação ao estande inicial e final, foi possível observar diminuição de valores dessas variáveis, tanto em MOPSS como em MOPCS para todos os tratamentos. O teste de tetrazólio mostrou que os prejuízos fisiológicos relacionados à elevação do potencial de inóculo apresentaram a mesma tendência que no teste de germinação, sendo possível observar em PSS, que a viabilidade das sementes foi superior a PCS. Através do teste de isolamento em placas com MEA ficou evidenciado que C. gloeosporioides é capaz de ser transmitido de semente – plântula, confirmando desta forma a capacidade infectiva do isolado transformado. Para identificar reações de defesa de cafeeiro em resposta à invasão por C. gloeosporioides o experimento foi conduzido em esquema fatorial 3 x 4 x 2 {(2 isolados de C. gloeosporioides –I2 e I2-T + 1 testemunha), 4 períodos de exposição das mudas aos isolados (6, 12, 24 e 48 horas) – coletas e 2 tipos de mudas: MOPCS e MOPSC } em DBC com 4 repetições. Para as análises enzimáticas foram plotadas curvas de progresso da atividade das enzimas por tempo de coleta e para os teores de fenóis solúveis totais o teste de Scott-Knott. Ficou evidenciado que C. gloeosporioides transformado geneticamente não perde sua capacidade de se manifestar no hospedeiro e ser percebido pelo mesmo, ativando desta forma os mecanismos de defesa da planta observados pelos picos de atividades da peroxidase e polifenoloxidase e do aumento dos teores de fenóis solúveis totais no caso de MOPSC.
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 de
Fungi 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.
Effect of temperature and leaf wetness on Phoma tarda and phoma leaf spot in coffee seedlings
(Editora UFLA, 2015-01) Lorenzetti, Emi Rainildes; Pozza, Edson Ampélio; Souza, Paulo Estevão de; Santos, Leandro Alvarenga; Alves, Eduardo; Silva, André Costa da; Maia, Fernanda Gonçalves Martins; Carvalho, Rejane Rodrigues da Costa
Phoma leaf spot is a major disease of coffee plants in regions with specific conditions of temperature and humidity. Despite the importance of environmental variables for disease progression, so far they have been poorly understood. Thus, we assessed the effect of different temperatures (15, 20, 25 and 30 oC) on mycelial growth, production and germination of conidia of Phoma tarda; and the same effect of temperature (15, 20, 25 and 30 oC) and leaf wetness duration (6, 12, 24, 36 and 48 hours) on fungal infection and severity of disease over time in coffee plants. Disease assessment was integrated in the area using the disease progress curve (AUDPC) and the infection processes were observed by scanning electron microscopy (SEM). The optimal temperatures for fungus growth, conidial production and germination in vitro were 22.9, 29.8, and 25.1 °C, respectively. Temperatures ranging from 15-20 °C significantly increased germ tube length and provided favorable conditions for pathogen infection through observation of early events such as cuticle separation from leaf tissue. The same temperature range combined with increasing leaf wetness periods, reached the highest value of the AUDPC of phoma leaf spot. Thus, it was found that both temperature and leaf wetness duration in the variables assessed and the difference in relation to temperature for in vitro growth and sporulation for in vivo tests were important.
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 de
Phytopathogenic 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.
Pigments, total soluble phenols and lignin levels of coffee seedlings inoculated with Colletotrichum gloeosporioides
(Editora UFLA, 2012-05) Maia, Fernanda Gonçalves Martins; Ogoshi, Cláudio; Vieira, Jucilayne Fernandes; Pierre, Rosana Oliveira; Maia, Jader Braga; Ribeiro Júnior, Pedro Martins; Abreu, Mário Sobral de
The objective of this work was to study the effects of different isolates of Colletotrichum gloeosporioides, as to pigment level (chlorophyll a, b and total), total soluble phenols and soluble lignin in coffee seedlings obtained by artificially inoculated tissue culture. The experiment was carried out in randomized block design in a 2 x 3 factorial scheme (2 genetic materials), 3 isolates (an isolate from mango fruits and another one from coffee plants), with 5 replicates and control (plants without inoculation). The plants were inoculated with a suspension of 2 x 10 6 conidia.ml -1 . The conidial suspension was sprayed on previously injured leaves. Leaves of inoculated plants were collected at 3 and 7 days after inoculation, except for leaves on the lower part of the plants. Afterwards, samples were prepared for the evaluation of chlorophyll, total soluble phenols and soluble lignin. The results showed that the presence of the pathogen in healthy and diseased plants significantly reduced the amount of chlorophyll. At 7 days after inoculation of healthy and diseased coffee plants higher total soluble phenol and soluble lignin levels were observed in response to the attack by Colletotrichum gloeosporioides.