Navegando por Autor "Oliveira, Júlia Marques"

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Effect of temperature and photoperiod on Pseudomonas syringae pv. garcae inoculum production
(Editora UFLA, 2024-11-12) Oliveira, Júlia Marques; Pozza, Edson Ampélio; Belan, Leônidas Leoni; Freitas, Marcelo Loran de Oliveira; Tedardi, Vitória Moreno
Bacterial halo blight (BHB), whose etiological agent is the bacterium Pseudomonas syringae pv. garcae, is one of the main diseases occurring in coffee (Coffea arabica L.) leading to losses in nurseries and fields. This study aimed to assess the effect of five temperatures (20, 25, 30, 35, and 40 °C) and three photoperiods (continuous light, 12-hour light/dark, continuous dark) on the P. syringae pv. garcae inoculum concentration and the BHB progression re sulted from this inoculum, in coffee seedlings. Using a factorial design (5 x 3) with four replicates, Petri dishes inoculated with P. syringae pv. garcae were incubated for 48 hours, and the concentrations and bacterial cell dimensions were measured. The resulting inoculum was then used to inoculate coffee seedlings at 23 ± 2 °C in one leaf pair by wounding inoculation using a multi-needle apparatus. The disease severity was assessed, and the area under the disease progress curve (AUDPC) was calculated. Significant interaction (p < 0.05) between temperature and photoperiod was observed for inoculum concentration and cell dimensions. The highest inoculum concentration (2.2 x 10⁹ CFU/ml) was recorded at 25 °C under continuous light. The largest bacterial cells (4.4 µm in length and 0.7 µm in width) resulted from temperatures of 30 °C with 12-hour light/dark. For the AUDPC of BHB, a difference (p < 0.05) was observed only between inoculum production temperatures. The highest AUDPC was recorded at 25 °C, with a gradual decline observed as the temperature increased.
Initial stages of infectious process of Pseudomonas syringae pv. garcae in coffee leaves
(Editora UFLA, 2019-07) Souza, José Otávio Gusmão de; Pozza, Edson Ampélio; Belan, Leônidas Leoni; Freitas, Marcelo Loran de Oliveira; Oliveira, Júlia Marques
Bacterial blight of coffee (Pseudomonas syringae pv. garcae) (PSG) has been causing damage and losses to coffee growing. However, initial stages of the infectious process should be described in order to understand the relationship cycle and to propose efficient management strategies. This study described the initial stages of infectious process of the PSG in coffee leaves over time. The bacterial penetration sites studied were stomata, leaf margins, and wounds. Coffee seedlings received 50μL inoculum suspension at marked points on the abaxial face and leaf margins, and around wounds. By 30 minutes, 1, 3, 6, and 12 hours after inoculation, leaf disks collected at inoculated points were analyzed with scanning electron microscopy. One hour after inoculation, bacterial groups could be seen as result of cell multiplication. Subsequently, the number of grouped bacteria increased proportionally over time. A growing population concentration was found near stomata, wounds, epidermal appendages, and wax layer on leaf margins and leaf tip. From these places bacteria were positioned in their long axis starting from structures, thus created a population gradient and displacement flow toward penetration sites. Initial stages of infectious process occurred in all penetration sites, thus it was not possible to determine a preferred pathway.
Progresso espaço-temporal da mancha aureolada em mudas de cafeeiro no viveiro
(Universidade Federal de Lavras, 2017-04-27) Oliveira, Júlia Marques; Pozza, Edson Ampélio
A mancha aureolada do cafeeiro (Pseudomonas syringae pv. garcae), tem ocorrido com frequência em viveiros e lavouras, preocupando produtores e técnicos por causar perdas consideráveis e ser de difícil controle. Para entender o progresso de epidemias, a origem e a quantidade do inóculo inicial, as formas de disseminação do patógeno, a influência dos fatores climáticos e ambientais na dispersão de patógenos e na infecção, e propor práticas de manejo da doença, é necessário conhecer a distribuição espacial das plantas doentes. Visto isso, o objetivo deste estudo foi caracterizar o progresso espaço-temporal da mancha aureolada a partir de inóculo inicial pré-definido, e sua relação com variáveis meteorológicas. O experimento foi realizado em viveiro de mudas, onde foram delimitados três canteiros ou blocos, com 1,05 m de largura por 2 m de comprimento, contendo 496 mudas cada um, dispostas em linhas e colunas. As mudas de cafeeiro da cultivar Catuaí Vermelho IAC 99 foram cultivadas em sacolas de polietileno (0,065 m de diâmetro por 0,20 m de altura), preenchidas com substrato. Quando as mudas atingiram o estádio de primeiro par de folhas definitivas, foram inseridas no centro do canteiro quatro mudas inoculadas com a bactéria P. syringae pv. garcae com sintomas da mancha aureolada. Houve epidemia da mancha aureolada nos canteiros 15 dias após a introdução do inóculo inicial, com duração de seis semanas e valor máximo de 6% de incidência. Houve dependência espacial e a doença atingiu até 55,18 cm de distância. Quanto maior o número de horas com molhamento foliar durante quatro dias consecutivos, em conjunto com menores valores de velocidade do vento por mais de oito dias, maior foi a incidência da mancha aureolada em mudas de cafeeiro no viveiro.
Proposed diagrammatic scale to assess heat injury in coffee seedling canopy
(Editora da Universidade Estadual de Maringá - EDUEM, 2023-04-28) Resende, Laís Sousa; Pozza, Edson Ampélio; Pereira, Renata Cristina Martins; Botrel, Élberis Pereira; Roteli, Karolaine de Cássia; Oliveira, Júlia Marques
A diagrammatic scale with five levels (0, 0.1 - 2.0, 2.0 - 6.0, 6.0 - 10, and 10 - 14) was developed and evaluated to measure the symptoms of heat injury in a coffee seedling canopy. The scale was constructed to increase assessment efficiency and align the estimations more closely with the actual values. Two assessments with the diagrammatic scale and one without were conducted with an interval of seven days. The evaluators using the proposed scale presented estimates with better levels of precision, accuracy, reproducibility, and repeatability than those using a conventional method. The proposed diagrammatic scale was shown to provide a reliable estimate for assessing the symptoms of heat injury on the canopy of in Coffea arabica L. seedlings. Therefore, it is possible to standardize heat injury evaluation methods using this diagrammatic scale, allowing for data comparisons with different cultivars.