Rhizobacteria are very important agents for the promotion of plant growth due to the
production of metabolites. Among these rhizobacteria, Streptomyces have great
potential in producing several bioactive compounds. The objective of this work was to
characterize morphologically isolated Streptomyces spp., to evaluate phosphate
solubilization and the production of indole acetic acid (IAA), the compatibility between
Streptomyces spp. and Bradyrhizobium japonicum and the antagonistic activity to the
pathogenic fungi Curvularia lunata and Colletotrichum sp. In addition, the objective
was to select isolates of Streptomyces spp. to be used as inoculants for both
soybean and cowpea culture in the region and to evaluate the effect of the doses on
the crops. The results showed that the isolates of Streptomyces presented varied
phenotypic characteristics, and the isolate UFT-St07 presented index of phosphate
solubilization. Regarding the production of indole acetic acid, the best results were
obtained in the presence of the L-tryptophan inducer, and the best isolates observed
were UFT-St04 and UFT-St08. Regarding the compatibility between Streptomyces
spp. and inoculant B. japonicum, it was observed that the highest inhibition indices
were observed with the isolates UFT-St01 and UFT-St09. The UFT-St05 and UFTSt07
isolates showed a positive effect on the biocontrol of Curvularia lunata, and the
isolates UFT-St04 and UFT-St07 in the biotype of Colletotrichum sp. Regarding the
use of Streptomyces in the soybean crop, better results were observed with the
isolate UFT-St07. In the field experiment the different dosages of inoculant were
efficient in maintaining the final plant stand, and the best dose of Streptomyces MIX
(UFT-St03, UFT-St06 and UFT-St08) was 300 mL for every 50 kg of seed. Regarding
the bean culture, strain UFT-St03 was the one that presented the best results. In
addition, the best inoculant doses were 300 and 400 mL / 50 kg seeds for all
parameters evaluated. Thus, it was possible to observe that Streptomyces has
potential in the biocontrol of phytopathogenic fungi and can be used as biofertilizer
because they have potential in the growth and incorporation of biomass, besides
favoring productivity.
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