The aim of this work was to evaluate the in vitro nitrogen-fixing activity and phosphate solubilizing activities of endophytic bacteria isolated from colosoana grass (Bothriochloa pertusa). The grass tissue was collected from root, stems and leaves from different agroecological zones in the municipality of Corozal, Sucre, Colombia. Each tissue underwent surface cleaning, maceration, and isolation of endophytic bacteria in R2A agar medium. Population density was determined by plate counts as CFU/g of tissue, morphotypes were then identified by shape, color, size, and appearance. Each morphotype was evaluated in vitro for nitrogen-fixation and phosphate solubilization in specific culture media. All results were analyzed using the statistical program R. The test results showed a significant differences in terms of population density of endophytic bacteria per type of tissue. A significant differences were found between population density with respect to tissue; the highest values were observed in roots (1.61 x 1010/g root), followed by stems (7.44 x 109/g stem) while the lowest values corresponded to leaves (5.42 x 109/g leaf). Significance was also found between population density with respect to other factors analyzed including: zone, farm and type of tissue. Results with the API20E identification kit confirmed the presence of the endophytic bacterium Aeromonas salmonicida and Pasteurella pneumotropica, which are capable of solubilizing phosphates and fixate nitrogen simultaneously.
Keywords: Bothriochloa pertusa, endophytic microorganisms, grass biofertilizers.