""Soilborne fungi cause devastating losses in many crops and are particularly difficult to control by chemical methods. Biocontrol agents (BCAs) represent a promising alternative, however, their efficacy needs to be optimized in order to improve their reliability and make them truly competitive with chemicals. A better understanding of the multitrophic interaction between BCA, pathogen and plant is needed to optimize antagonist selection and application. . The aim of this work was to investigate the molecular mechanisms involved in the interaction between the BCA Bacillus amyloliquefaciens (isolate BO7) and the vascular wilt fungus Fusarium oxysporum f.sp. lycopersici (Fol). BO7 was selected based on its strong in vitro activity against Fol, and its efficacy to reduce vascular wilt disease caused by Fol on tomato plants. Scanning electron microscopy evidenced that BO7 adhere to fungal hyphae and efficiently colonize tomato roots. . Microscopic analysis of Fol hyphae treated with BO7 culture filtrate revealed growth inhibition and dramatic alterations in hyphal morphology. Evaluation of fungal knockout strains evidenced an increased sensitivity of Fol mutants affected in cell wall composition and biosynthesis. . Chemical characterization of the low molecular weight fraction of the BO7 culture filtrate by HPLC, 1H and 13C-NMR analysis identified three new lipopeptides (1-3) of the surfactin family. The compounds were based on the heptapeptide Glu-Leu-Leu-Ala-Asp-Leu-Leu, N-acylated to the N-terminal by an (R)-3-hydroxy fatty acid with linear alkyl chains from 16:0 to 18:0 (1-3, respectively). Among the new surfactins, compound 3 displayed the strongest antifungal activity. These results show that production of surfactin lipopeptides is a major factor in biocontrol activity of B. amyloliquefaciens BO7 against Fol and suggest a key role of the fungal cell wall in the antifungal mechanism of these compounds.. In summary, we propose that the three-way interaction between bacterial isolates, genetically characterized Fol mutants and the tomato plant provides an excellent experimental model for elucidating basic mechanisms of interaction between bacterial BCAs and their biomolecules and plant pathogenic fungi. This research should open new ways for optimizing BCAs application in biocontrol of soilborne plant pathogens.. ""
New insights on the mechanisms of interaction between biocontrol bacteria and Fusarium oxysporum in the rhizosphere of tomato plant
LIMA, Giuseppe;VITULLO, Domenico;
2011-01-01
Abstract
""Soilborne fungi cause devastating losses in many crops and are particularly difficult to control by chemical methods. Biocontrol agents (BCAs) represent a promising alternative, however, their efficacy needs to be optimized in order to improve their reliability and make them truly competitive with chemicals. A better understanding of the multitrophic interaction between BCA, pathogen and plant is needed to optimize antagonist selection and application. . The aim of this work was to investigate the molecular mechanisms involved in the interaction between the BCA Bacillus amyloliquefaciens (isolate BO7) and the vascular wilt fungus Fusarium oxysporum f.sp. lycopersici (Fol). BO7 was selected based on its strong in vitro activity against Fol, and its efficacy to reduce vascular wilt disease caused by Fol on tomato plants. Scanning electron microscopy evidenced that BO7 adhere to fungal hyphae and efficiently colonize tomato roots. . Microscopic analysis of Fol hyphae treated with BO7 culture filtrate revealed growth inhibition and dramatic alterations in hyphal morphology. Evaluation of fungal knockout strains evidenced an increased sensitivity of Fol mutants affected in cell wall composition and biosynthesis. . Chemical characterization of the low molecular weight fraction of the BO7 culture filtrate by HPLC, 1H and 13C-NMR analysis identified three new lipopeptides (1-3) of the surfactin family. The compounds were based on the heptapeptide Glu-Leu-Leu-Ala-Asp-Leu-Leu, N-acylated to the N-terminal by an (R)-3-hydroxy fatty acid with linear alkyl chains from 16:0 to 18:0 (1-3, respectively). Among the new surfactins, compound 3 displayed the strongest antifungal activity. These results show that production of surfactin lipopeptides is a major factor in biocontrol activity of B. amyloliquefaciens BO7 against Fol and suggest a key role of the fungal cell wall in the antifungal mechanism of these compounds.. In summary, we propose that the three-way interaction between bacterial isolates, genetically characterized Fol mutants and the tomato plant provides an excellent experimental model for elucidating basic mechanisms of interaction between bacterial BCAs and their biomolecules and plant pathogenic fungi. This research should open new ways for optimizing BCAs application in biocontrol of soilborne plant pathogens.. ""I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
