Diazotrphic and phosphate solubilizing bacteria isolated from Weinmannia tomentosa and Escallonia myrtilloides Colombia's high andean forest species

Abstract

Encenillo (Weinmannia tomentosa Lf) and pagoda (Escallonia myrtilloides Lf) are dominant native tree species that can be found in the forests of the complex Andean Guerrero (Cundinamarca, Colombia). Forty two phosphorus-solubilizing bacteria and 125 nitrogen-fixing strains were isolated from the rhizosphere of these trees, out of which the microbial strains presenting the best five results of dissolution of phosphate and acetylene reduction by plant species were selected. The diazotrophic strains selected were identified as close to Enterobacter gergoviae, Alcaligenes sp. (E13C and E12E strains), Enterobacter sp. (E14C.2 strain), Pseudomonas sp., Sphingomonas sp., Paenibacillus sp., Achromobacter sp., Flavobacterium adoratum, and Klebsiella pneumoniae, and as phosphate-solubilizingbacteria near to Pantoea agglomerans, Pantoea sp., Brevudimonas sp., Enterobacter sp. (E6C.1 strain), Burkholderia cepacia, Arthrobacter sp., Aeromicrobium sp., Corynebacterium sp., Pimelobacter sp. and Micrococcus sp. In order to perform preliminary in vivo tests with the chosen microorganisms, it was inoculated bacterial mixture to encenillo and pagoda seedlings and evaluated their longitudinal growth for three months under greenhouse conditions. The major averages were obtained with the inoculation of Enterobacter gergoviae and Pantoea sp. in encenillo seedlings (average increase of 51% and 57% greater than the controls without microbial inoculation and sterile molasses medium, respectively) and the mixture of all selected bacteria in pagoda (Stimulation of 16% and 32% compared to controls molasses and without bacterial inoculation, respectively). The results showed that all the combinations using microbial inocula significantly stimulated longitudinal growth (Duncan multiple range test P<0.05). The synergism shown by co-inoculation of diazotrophic bacteria and phosphate solubilizing bacteria indicate the potential of these microorganisms as plant growth promoters and biofertilizers.