Gabriel A Rejón-Martínez, Diana E Ríos-Muñiz, Erika A Contreras-Leal, Zahaed Evangelista-Martínez


Background: Crop microbial pathogens reduce the production and quality of agricultural products. They cause substantial increase costs for producers of fruits, vegetables, and ornamental plants with negative consequences on economy and food security at household, national and global levels. Annually, the losses represent around 40% to 50% for root crops, vegetables, and fruits. Chemical control with fungicides can prevent, kill, mitigate, or inhibit the growth of plant pathogenic fungi. Nevertheless, biological control with microorganisms and natural molecules is an increasingly popular alternative to protect crops. Objective: Here, the antagonist activity of soil Streptomyces sp. Y20 against the pathogenic fungi causing diseases in plants and fruits was evaluated. Methodology: Streptomycetes bacteria was isolated from soils collected at open field cultures of local farms with tomato. The antagonism was evaluated in vitro via a dual confrontation experiment against fungal species of Fusarium, Lasiodiplodia, Colletotrichum, Aspergillus, Botrytis, and Sclerotium. Streptomyces sp. Y20 was characterized phenotypically and molecularly identified by the 16S rDNA gene. The biosynthetic gene clusters for polyketide synthases (PKS Type I) and non-ribosomal peptide synthase (NSPS) were detected. Results: Preliminary, the isolate Y20 was selected by the higher antagonism against F. oxysporum f sp. lycopersici. Taxonomic characterization of the isolate Y20 by the analysis of the 16S rDNA sequence led to its identification as member of Streptomyces genus. Spore surface morphology by Scanning Electronic Microscopy (SEM) showed barrel-like spores. Antagonistic activity of Streptomyces sp Y20 was comparable to the commercial strain S. lydicus WYEC108 (P > 0.5). However, there was a superior antagonism of Y20 strain versus the commercial strain WYEC108 against F. oxysporum f sp. lycopersici, Fusarium sp. CDBB1172, F. oxysporum, Lasiodiplodia sp., and Aspergillus sp. (P < 0.05). Implications: Soil streptomycetes with in vitro antagonistic activity on plant pathogenic fungi could be a natural alternative to the use of chemical fungicides to control plant diseases. Conclusion: This study presented a novel soil Streptomyces specie which showed in vitro antagonism against a diversity of plant pathogenic fungal species. Streptomyces strain Y20 could be used as a biocontrol agent.


Biological control; Streptomyces; antagonism; antifungal; fungal pathogen

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