Antifungal activity of Streptomyces sp. CACIS-2.15CA, as a potential biocontrol agent, against some soil-borne fungi

Abstract

BackgroundSoil biocontrol streptomycetes are considered as ecofriendly agents, which inhibit the growth of multiple fungal pathogens. In addition, the majority of species are considered non-plant pathogenic, and they are beneficial to plant growth and soil salinity because they produce broad bioactive secondary metabolites, i.e., polyenes, volatile organic compounds, fatty acids, plant growth regulators, and diversity of extracellular hydrolytic enzymes. Therefore, this study aimed to select, characterize, and perform the molecular identification of a streptomycete isolate by in vitro antagonistic activity against some soil-borne fungi.ResultsTwenty-five isolates obtained from the Germplasm Bank of Actinomycetes were tested in dual confrontation assay to determine their inhibitory activity against the growth of Colletotrichum musae. In addition, 22 isolates (88%) inhibited the mycelial growth of C. musae, particularly the isolate CACIS-2.15CA, which showed the highest antagonistic activity. Furthermore, an antifungal evaluation using additional fungal species was performed. The CACIS-2.15CA isolate exhibited a high inhibitory activity against Phytophthora capsici, C. musae, Botrytis cinerea, Lasiodiplodia sp., Sclerotinia sp., Fusarium oxysporum, F. oxysporum f sp. lycopersici Fusarium sp., and Aspergillus sp. at percentages ranging from 7.3 to 61.2%. The isolate was characterized by its morphology and physiology and by the presence of genetic biosynthetic clusters for non-ribosomal polyketide synthases and polyketide synthases type I and II using polymerase chain reaction assays; the selected strain harbored genes for NRPS and PKS type I clusters. Moreover, the isolate was molecularly identified as a member of Streptomyces genus based on the partial sequence of the 16S rRNA gene. Based on its morphological and physiological characteristics, the CACIS-2.15CA isolate belongs to Streptomyces genus.ConclusionGiven the aforementioned characteristics, Streptomyces sp. CACIS-2.15CA can be a potential biocontrol agent against various fungal strains.