MOLECULAR IDENTIFICATION AND ANTAGONISTIC POTENTIAL OF THREE STRAINS OF Streptomyces AGAINST PHYTOPATHOGENIC FUNGI

Actinobacteria belong to a group of abundant microorganisms in natural ecosystems. Out of these microorganisms, particularly from the species of the genus Streptomyces, most of the antibiotics that are used for human health have been characterized and identified. However, they are seldom used as antagonists in agricultural systems; despite it is plausible that species of Streptomyces can control important root pathogens. The objective of this study was to obtain the molecular identification and characterization of three Streptomyces strains by confronting them against phytopathogenic fungi and oomycetes, in order to determine the in vitro antagonistic potential and the effect of volatile compounds produced. The strains of Streptomyces were molecularly identified through the sequence of 16S of the RNAr such as: Streptomyces mauvecolor (B21), Streptomyces lasiicapitis (B22) and Streptomyces olivochromogenes (B37) which showed antagonistic potential in vitro against Rhizoctonia solani, Fusarium oxysporum and Phytophthora capsici. S. mauvecolor showed an average percentage of radial growth inhibition (PICR) for the three pathogens of 62.88 %, S. lasiicapitis of 98.72 % and S. olivochromogenes of 83.58 %. Similarly, out of the three pathogens, R. solani was inhibited in greater proportion by the three strains (93.85 %). A relevant fungistatic action was observed over P. capsici, an economically important oomycete, with 100 % inhibition at 24, 48 and 72 h of exposure with S. lasiicapitis, first reported as antagonist of root pathogens. The use of these species of Streptomyces with high levels of antagonism against pathogens of economically important crops, represents an alternative of low environmental impact.