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Item Temporal analysis of Phoma leaf spot of coffee plants at different altitudes(Universidade Federal de Viçosa, 2025-04-25) Silva, Humberson Rocha; Pozza, Edson Ampélio; Freitas, Aurivan Soares de; Freitas, Marcelo Loran de Oliveira; Barbosa Junior, Mauro Peraro; Cirillo, Marcelo AngeloPhoma leaf spot (Phoma spp.) of coffee causes losses of between 15 and 43%, and presents significant variability over time and space, especially in mountain coffee production. Thus, the objective of this study was to evaluate the behavior of this disease at different altitudes and to use time series techniques and regression models to explain disease behavior. The experiment was conducted over two years (from September 2013 to August 2015) with monthly evaluations in a Coffea arabica L. plantation. The incidence and severity progress curves showed irregular behavior most of the time, typical of the disease. Higher altitudes provided higher disease incidence and severity values. Only the incidence and severity progress curves at the altitude of 1143.2 m showed significant autocorrelation over time. Thus, the first-order autocorrelation structure, AR(1), was incorporated in the estimates of the parameters of the linear and nonlinear models. Only the months from February to June/July 2014 were considered, when the disease progressed regularly. The rates obtained for the incidence, overall mean of the 85 points and mean altitude of 1143.2 m, were 5.2 and 4.6%, respectively, while the estimated rates for the severity data under the same conditions were 0.3 and 0.1%, respectively. These values represent the expected increase in incidence and severity each month. The Phoma leaf spot presents complex temporal dynamics, influenced by microclimatic variables associated with altitude.Item 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 MorenoBacterial 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.