Avaliação do potencial biotecnológico de Streptomyces sp. para biocontrole de fungos fitopatogênicos de espécies agrícolas de importância econômica: biocontrole de fitopatógenos por Streptomyces sp.

Abstract

Fungi are the phytopathogens that most substantially affect global agricultural productivity. The development of sustainable strategies and approaches for the control of phytopathogenic fungi and their respective diseases has become an increasingly relevant topic because of growing consumer awareness regarding the issue of pesticides. Actinobacteria are organisms mostly found in soil, capable of developing symbiotic relationships with plants and promoting several advantages for their hosts, including resistance to biotic stresses. Streptomyces is a genus of actinobacteria particularly known for its robust secondary metabolism and high biotechnological potential in the production of antimicrobial compounds, but studies also point to the potential of such bacteria in the biological control of plant diseases. The present study aims to evaluate the antifungal potential of the MG04 strain of Streptomyces sp., isolated from mangrove sediment, against phytopathogenic fungi of commercial interest in order to obtain a general overview of the strain's antagonistic properties and guide potential applications in biocontrol and management of diseases in plants. To this end, in-vitro double-culture antagonism tests, cell culture filtrate antagonism and voltaile organic compounds antagonism essays were carried in addition to investigation of the impact of cultivation conditions on the antifungal potential. The antifungal potential against phytopathogens was measured against Alternaria alternata, Bipolaris sp., Ceratocystis paradoxa, Colletotrichum sp.; Lasiodiplodia euphorbicola; Lasiodiplodia pseudotheobromae; Rhizopus microsporus; Sphaceloma sp. (CNPUV 102) and Sclerotinia sclerotium. To this end, the double plate culture assay (32.20% to 79.67% inhibition), diffusion test in cell culture filtrate agar (10.54% to 53.57% inhibition), of production of volatile organic compounds (19,70% to 86,68% inhibition) and OSMAC methodology adjusted with Plackett-Burman design was applied to evaluate the variables with the most significant impact on antimicrobial productivity. Of the nine fungi tested, 8 showed considerable growth inhibition, particularly Bipolaris sp., Colletotrichum sp. and Sphaceloma sp., causative agents of Bipolaris Spot, anthracnose and cassava superelongation, respectively.