title: Anti-phytopathogen potential of endophytic actinobacteria isolated from tomato plants (Lycopersicon esculentum) in southern Brazil, and characterization of Streptomyces sp. R18(6), a potential biocontrol agent.
abstract: Tomato plants (Lycopersicon esculentum) are highly susceptible to phytopathogen attack. The resulting intensive application of pesticides on tomato crops can affect the environment and health of humans and animals. The objective of this study was to select potential biocontrol agents among actinobacteria from tomato plants, in a search for alternative phytopathogen control. We evaluated 70 endophytic actinobacteria isolated from tomato plants in southern Brazil, testing their antimicrobial activity, siderophore production, indoleacetic acid production, and phosphate solubility. The actinomycete isolate with the highest antimicrobial potential was selected using the agar-well diffusion method, in order to optimize conditions for the production of compounds with antimicrobial activity. For this study, six growth media (starch casein-SC, ISP2, Bennett's, Sahin, Czapek-Dox, and TSB), three temperatures (25 degrees C, 30 degrees C, and 35 degrees C) and different pH were tested. Of the actinobacteria tested, 88.6% showed antimicrobial activity against at least one phytopathogen, 72.1% showed a positive reaction for indoleacetic acid production, 86.8% produced siderophores and 16.2% showed a positive reaction for phosphate solubility. Isolate R18(6) was selected due to its antagonistic activity against all phytopathogenic microorganisms tested in this study. The best conditions for production were observed in the SC medium, at 30 degrees C and pH 7.0. The isolate R18(6) showed close biochemical and genetic similarity to Streptomyces pluricolorescens.
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Básicas da Saúde, Univrsidade Federal do Rio Grande do Sul, Rua Sarmento Leite, 800, sala 158, CEP 90050-170, Porto Alegre, RS, Brazil.
authors.forename: Margaroni Fialho
authors.initials: MF
authors.lastname: de Oliveira
authors.forename: Mariana Germano
authors.initials: MG
authors.lastname: da Silva
authors.forename: Sueli T
authors.initials: ST
authors.lastname: Van Der Sand
mesh_terms: D039903:Actinobacteria / Q000302:isolation & purification / Q000502:physiology*; D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000494:pharmacology; D000898:Antibiosis; D000935:Antifungal Agents / Q000494:pharmacology; D018407:Bacterial Physiological Phenomena; D001938:Brazil; D005658:Fungi / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum / Q000382:microbiology*; D010572:Pest Control, Biological; D010710:Phosphates / Q000737:chemistry; D010935:Plant Diseases; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000096:biosynthesis; D013302:Streptomyces / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D007210:Indoleacetic Acids; D010710:Phosphates; D017262:Siderophores; C030737:indoleacetic acid