Resumen en inglés

The bacterial or vascular wilt MV, of eucalyptus, caused by R. solanacearum, is a disease that affects the production in the different phenological phases of the plant, being reported as a limitation in the production of seedlings in the nursery and also responsible for the death of trees in field. The objective of the research was to identify the causal agent of eucalyptus vascular wilt, Eucalyptus urograndis in the department of Córdoba. In the first phase of this study, samples of infected plants were taken in the field, which were placed in humid chambers for 72 hours and the exudate that appeared from the samples was sown in semi-selective TZC and SMSA media. Six isolates with watery-looking and reddish colonies were obtained, they were purified and KOH, Gram stain and oxidase tests were performed. These were subjected to a hypersensitivity test in non-host tobacco plants (Nicotina tabacum) by inoculating them with a concentration of 108 cfu / ml of R. solanacearum, in the same way pathogenicity tests were carried out in the host plant E. urograndis, clone 14 susceptible to MV. For each isolate, five plants were inoculated and the control was inoculated with distilled water. The inoculation was carried out on the stem 5 cm above its base, depositing 0.5 ml of the bacterial solution at the previously evaluated concentration (108ufc / ml), then the wound was covered with cotton and sealed with parafilm. Destructive sampling was carried out at 104 days post inoculation, to describe external and internal symptoms, of the six isolates, two caused pathogenicity, in eucalyptus and hypersensitivity in tobacco, these two isolates were characterized by PCR and identified as strain 1 and strain 2. A second experiment was established where the resistance of 14 clones of the cultivar E. urograndis susceptible to vascular wilt was determined, taking as reference clone 14. For each clone there were five plants of which two were inoculated with the strain 1, two with strain 2 and one plant with distilled water as a control. The inoculation was carried out with the methodology and concentration described above. The monitoring of symptoms in the different clones was carried out every two days for 50 days; finally, 54 days after inoculation, a destructive sampling was carried out, the external and internal symptoms of the inoculated stems were described, evaluating the vascular infection. The presence of bacterial vascular involvement was determined by the flow test in a test tube with water. Finally, to verify the presence of the inoculated bacteria, fragments of the stems with symptoms were placed in humid chambers, the bacterial exudate produced was seeded in the TZC medium and the respective Gram and oxidase tests were carried out. A qualitative analysis was carried out comparing microbiological and molecular characteristics of the isolates, in addition the degree of damage was evaluated using the proposed scale, which allowed classifying the level of damage caused by the six strains in clone 14. In conclusion, the capacity of the six isolates to cause vascular damage in clone 14, highly susceptible and two of them were identified as strains by means of the PCR technique as R. solanacearum, which were evaluated in 14 clones, where all showed susceptibility to vascular wilt , concluding that the phytosanitary risk that this bacterium represents in eucalyptus, which must be taken into account when implementing disease management plans.