Isolamento e caracterização de bactérias solubilizadoras de fosfato da rizosfera de eucalyptus sp

Abstract

The inoculation of phosphate solubilizing microorganisms, with or without mycorrhizal fungi, can be an alternative to reduce de production costs of eucalyptus due to the decrease in phosphate fertilization spending. Thus, the objective of this work was to isolate and characterize phosphate solubilizing bacteria from the rhizosphere of Eucalyptus sp. aiming their co-inoculation with ectomycorrhizal fungi. Among the 24 isolates of bacteria originating from the rhizosphere soil of Eucalyptus, 12 are from phylum γ-Proteobacteria belonging to the family Enterobacteriaceae (Enterobacter, Kluyvera and Klebsiella); 9 from β-Proteobacteria (Burkholderia); one from Actinobacteria (Curtobacterium) and one from Firmicutes (Enterococcus). The phosphate solubilization index, calculated by dividing the diameter of the halo of bleaching by the diameter of the colony, ranged from 0 to 11, with the species Enterococcus avium showing the greatest potential to solubilize CaHPO4 in vitro. The production of acidity in the Glucose-Yeast Extract media by the rhizosphere bacterial isolates was significant, however, CaHPO4 solubilization ability is not correlated with the acidification of the medium. Some bacterial isolates promoted strong inhibition of growth of Pisolithus sp., isolate H4111, while others did not cause this phenomenon. The isolates RE 56 (Enterococcus avium), RE 41 (Burkholderia cepacea), RE 52 and RE 30 (both Burkholderia pyrrocinia) were those which showed the highest potential for utilization in co-inoculation experiments with ectomycorrhizal fungi.