The objective of this study was to evaluate in vitro biochemical activity of rhizosphere microorganisms from vanilla plants with potential as biofertilizers. The taxonomic identity of the most efficient microorganisms was confirmed using phenotypic methods. Isolates were obtained from vanilla plants grown under shade house conditions in the municipality of Sopetrán (Antioquia department, Colombia) during 2011. The most effective solubilizers of inorganic phosphate were bacteria identified as Serratia sp. and Pseudomonas koreensis. The most effective organic-phosphate solubilizing microorganism was the fungus Plectosphaerella cucumerina. In terms of celullose-hydrolytic activity Penicillium griseofulvum and Aspergillus fumigatus stood out as the most effective organisms. Bacteria belonging to the Bacillus cereus complex and to Serratia sp. showed the highest proteolytic/ammonifying activity. Finally, three isolates from Pseudomonas koreensis exhibited the highest nitrogen fixation ability. Moreover the presence of the NifH gene, responsable for this metabolic activity, was confirmed for these bacteria through PCR. The functional diversity of the microorganisms here presented suggests that there is potential for their use as biofertilizers in the vanilla crop.
Keywords: cellulytic microorganisms, proteolytic microorganisms, phosphate solubilizers, asymbiotic N2-fixers.