Navegando por Autor "Souza, José Otávio Gusmão de"

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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.
Manganese and fluorine suppress bacterial blight on coffee seedlings grown in a nutrient solution
(Editora UFLA, 2021) Velloso, Jeanny Alice; Pozza, Edson Ampelio; Pozza, Adelia Aziz Alexandre; Silva, Humberson Rocha; Pérez, Cristian David Plaza; Souza, José Otávio Gusmão de
The use of manganese (Mn) and fluorine (F) in the management of bacterial blight were evaluated in coffee seedlings grown in a nutrient solution. The experiment was carried out with the cultivar Catuaí Vermelho IAC 99. The treatments consisted of the combination of five doses of Mn with five of F, applied via leaf, using Mn sulfate and sodium fluoride, in a 5x5 factorial scheme. The plants were inoculated with bacterial suspension seven days after foliar application of F and Mn doses. The incidence and severity assessments were performed at an interval of 24 hours for 10 days. Photosynthetic activity was assessed using the infrared gas analyzer. Stomatal conductance, photosynthesis, transpiration, PAR radiation and internal CO2 were ana lyzed. The chlorophyll content was calculated indirectly. The leaf analysis was performed by digestion in HNO3 to determine the levels of Mn. Variables such as Area Under Incidence Disease Progress (AUIDP), Area Under Severity Disease Progress (AUSDP), chlorophyll a, b, and total concentrations and photosynthesis were submitted to the Shapiro-Wilk test. The treatment means were subjected to linear regression analysis. Data were analyzed using software R. There was a significant interaction (P <0.05) between the concentrations of Mn and F for the AUIDP and (AUSDP). Doses between 0.7 and 1.4 g L-1 of Mn combined with doses of 0.10 to 0.12 g L-1 of F were more effective in suppressing the bacterial blight, after analysis for both variables. The increase in Mn concentrations in leaves reduced liquid photosynthesis. The interaction between Mn and F suppressed the bacterial blight intensity of the coffee plants in nutrient solution.