Phosphate solubilization, indole acetic acid synthesis and biocontrol by streptomyces isolates

Actinobacteria of the genus Streptomyces have great potential in producing several bioactive compounds. With that, the objective was to characterize morphologically isolates of Streptomyces, to evaluate the phosphate solubilization and the production of indole acetic acid (IAA) and the antagonistic activity to the pathogenic fungi Curvularialunata andColletotrichum sp. The morphological characterization presented eight-gram positive isolates from the nine evaluated. Six isolates presented a colony greater than 2 mm, seven with elevated colony and five transparent. All isolates presented positive results to produce filamentous and branched hyphae, and only one isolate (UFT-St03) did not present mycelium staining. As for the phosphate solubilization capacity test, only one UFT-St07 isolate presented an index of phosphate solubilization. To produceAIA, the best results were superior in the presence of the L-tryptophan inducer, the best observed for UFT-St04 (3.8 µgmL-1) and UFT-St08 (3.09 µgmL-1). For the antagonism evaluation, the UFT-St05 and UFT-St07 isolates presented percentages of inhibition against the C. lunata pathogen of 90 and 93.7% inhibition, respectively. As for the Colletotrichum sp.pathogen, higher percentages of inhibition of the isolates UFT-St04 (85.2%) and UFT-St07 (87.6%) were observed.