Identification and Evaluation of Endophytic Bacteria Against Phytopathogenic Fungi in vitro Assay

Susana González-Morales, Azalia Magdaleno-López, Dulce Flores-Rentería, Adalberto Mendoza and Rebeca Valdés

Background and Objective: Plant health problems are a major cause of economic losses in crops worldwide. In recent years, it has been shown that endophytic microorganisms associated with many plant species produce secondary metabolites with antifungal action; among these are endophytic bacteria, which can promote plant growth and control the growth of phytopathogenic fungi. The objective of this study was to identify antagonistic bacteria against phytopathogenic fungi and evaluate their effectiveness in tomato seedlings. Materials and Methods: Strains of endophytic bacteria were isolated from pine roots and identified by amplifying the 16S gene. The isolated and identified strains were evaluated in vitro in antagonistic tests against fungi of the genera Alternaria and Fusarium. A greenhouse trial was conducted with tomato seedlings of the Floradade variety 15 days after transplant. The species Bacillus atrophaeus, Bacillus subtilis and Brucella intermedia were identified by molecular identification. Results: The strain that induced the highest percentage of inhibition was found to be a strain of Brucella intermedia, presenting values of up to 50% inhibition of the evaluated fungi. Highly significant differences were shown in the in vitro antagonism tests with the evaluated endophytic bacteria strains. Bacillus atrophaeus increased fresh root biomass by 46% and both Brucella intermedia and Bacillus atrophaeus increased fresh plant biomass by 34%. Conclusions: The data suggest that the strains shown here inhibit the growth of phytopathogenic fungi and promote plant development in greenhouses.

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