Sensibilidade in vitro e in vivo de isolados de Pseudomonas syringae pv. Garcae ao cobre

Abstract

In this study, isolates of Pseudomonas syringae collected from coffee plantations, with symptoms of leaf spots, were tested to determine sensitivity to different concentrations of copper. The experiments were carried out in vitro using 17 isolates and 3 replications. In this experiment, suspensions of each isolate, with the concentration adjusted on a spectrophotometer to 1.1x109 cfu/ml, were sown in Petri dishes, containing MMCC culture media with the following concentrations: 0; 0.05; 0.10; 0.15; 0.25; 0.4 and 0.6 mM (Cu (OH)2). Next, 3 isolates that showed high, intermediate and low sensitivity to copper were chosen for the in vivo experiment. The Catuaí Vermelho IAC 99 cultivar, susceptible to halo spot, was used, previously sprayed with 2.5 ml/L of mineral oil and 7.10g/L of copper hydroxide. There were 7 treatments, represented by inoculation with the 3 previously selected isolates, on plants sprayed and not sprayed with copper hydroxide and the control without inoculation and sprayed with copper hydroxide and 12 plants per plot. The inoculations were carried out in the plant growth chamber of the DFP/UFLA Epidemiology Laboratory, at a temperature of 25o C, under high humidity, where the plants remained until the end of the evaluation. The isolates UFLA 06, UFLA 112, UFLA 113, UFLA 114, UFLA 148, UFLA 507 were considered resistant to copper, as in vitro colony growth was observed at all concentrations tested. Isolates UFLA 21, UFLA 48, UFLA 138-1, UFLA 144 and UFLA 896 showed growth only at concentrations up to 0.4 mM of (Cu (OH)2), being considered intermediate. The isolates UFLA 79, UFLA 98, UFLA 126, UFLA Guapé and UFLA 129, this one from P. syringae pv. tabaci, showed growth only at concentrations up to 0.25 mM of CuSO 4, being considered sensitive to copper, as well as the isolate UFLA57 with growth up to 0.15 mM of (Cu (OH)2). With the results, isolates UFLA 148 were randomly selected for in vivo tests on the Catuaí Vermelho IAC 99 cultivar, as resistant to copper, UFLA 129, as intermediate resistance, and UFLA 57 as sensitive. When evaluating the incidence and severity of the disease, there were significant differences between isolates and the application of copper. Plants inoculated with the UFLA 148 isolate and without copper application showed the highest severity of the disease (AACPD), in relation to the other treatments, which did not differ from each other. Analyzing the results, no relationship was found between the sensitivity of the isolates to copper in vitro and in vivo, as the application of copper hydroxide caused a reduction in the disease caused by the UFLA 148 isolate, the most resistant to copper in in vitro tests.