Examinando por Autor "Urango Esquivel, Naudith"
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Publicación Acceso abierto Evaluación de la resistencia de genotipos de frijol caupí (Vigna Unguiculata L.) a marchitez por Sclerotium Rolfsii en casa malla(2023-02-28) Urango Esquivel, Naudith; Campo Arana, Rodrigo OrlandoThe cowpea bean crop in Colombia is of great importance, mainly in the Caribbean region, being a basic agricultural alternative in the diet of low-income households; however, one of the limitations of the crop is the presence of the phytopathogenic fungus Sclerotium rolfsii Sacc. which causes yield losses of up to 53.4%. Among the management strategies, the use of resistant genotypes is an ideal tool for disease management, which led to the present research whose objective was to evaluate the resistance of cowpea genotypes (Vigna unguiculata (L.) Walp) to Sclerotium wilt under net house conditions. The study consisted of two experiments, the first one determined the resistance of 12 genotypes to two Sclerotium spp. strains, this was established under a completely randomized design with 12x3 factorial arrangement, with a total of 36 treatments with 3 replications (each experimental unit consisted of 1 plant, for a total of 432 experimental units), the data collection was carried out every seven days for 35 days. Resistance was evaluated considering epidemiological variables PI (incubation period), PL (latency period), incidence and severity of the disease. In the second experiment, the phenological stage of cowpea most susceptible to the disease was determined, the materials were inoculated at four phenological stages of the crop cycle, established under a completely randomized design with a 12x4 factorial arrangement for a total of 48 treatments with 3 replications (each experimental unit was a bag with three plants for a total of 288 experimental units). Evaluations were carried out every seven days for 21 days after inoculation and the variables of response, incidence and severity of the disease were measured. Disease intensity index values were fitted to growth models, and cumulative disease progress curves over time were obtained and epidemiological parameters were calculated. Data were transformed into ranges and analyzed by nonparametric statistics, followed by a Duncan 5% test. The percentages of emergence, incidence, severity, intensity index, incubation period, and latency period showed differences depending on the strain, genotype, and inoculation time evaluated. Disease intensity index values were best fitted to the monomolecular model. The Monteria strain was the most aggressive; whereas, seven genotypes were classified as resistant, two tolerant and three susceptible to S. rolfsii. The interaction between genotype and phenological stage was significant at 5%, with the V0 stage (at planting) being the most susceptible to the disease, representing the critical period of infection. The results suggest that genotypes IT-86, Negro, Gurgueia and BRS-Jurua were more resistant and can be used as parents in breeding programs for the management of Sclerotium wilt.Publicación Acceso abierto Identificación del agente causal de la marchitez vascular del eucalipto, Eucalyptus urograndis en el departamento de Córdoba(2022-01-24) Martínez Estrada, Luisa Fernanda; Campo Arana, Rodrigo Orlando; Urango Esquivel, Naudith; Reforestadora del SinúThe 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.