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ABSTRACT
The bioactive compounds produced by Streptomyces spp. bacteria can inhibit and reduce the incidence of phytopathogenic fungi in agricultural crops. In this study, two Streptomyces strains 6(4) and R18(6) were tested separately and in a consortium and demonstrated antifungal activity against the phytopathogenic fungus Pyrenophora tritici-repentis (Ptr) that causes tan spots in wheat plants. Streptomyces isolates inhibited mycelial growth and they induce changes in hyphal development in the germination of Ptr. In the dual culture assay, the Streptomyces 6(4) strain inhibited growth of Ptr by 44% and in the agar well diffusion assay, produced the largest inhibition halos when the crude extract was tested (≥20 mm). The detached leaf assay showed that Streptomyces 6(4) and R18(6) strains and consortium crude extracts, reduced the disease index on the leaves of wheat, with 100, 90, and 95% biocontrol efficacy, respectively. Inoculating seeds with the propagules of spores of the same strains, 6(4), R18(6) and consortium, also resulted in biocontrol of the pathogen on detached leaves, although with 48, 53.08 and 60% biocontrol efficacy respectively. Therefore, we can conclude that the crude extracts of these isolates have the potential to control the fungus Pyrenophora tritici-repentis and reduce the symptoms of tan spot in wheat.
Acknowledgments
This research was supported by the Brazilian federal government agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
Disclosure statement
No potential conflict of interest was reported by the author(s).