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Molecular and cellular interactions between the plant protective bacterium Bacillus subtilus 49b and the plant pathogen Fusarium oxysporum causing tomato root and foot rot

Final Activity Report Summary - INTERBAC (Molecular and cellular interactions between the plant protective bacterium Bacillus subtilus 49b and the plant pathogen Fusarium oxysporum ...)

Biocontrol of phytopathogenic fungi by Bacillus subtilis is accomplished by antibiosis, induced systemic resistance, competition for nutrients and niches or plant growth promotion.

This study focuses on mechanisms involved in the biocontrol activity of Bacillus subtilis strain B49b against Fusarium oxysporum f. sp. radicis lycopersici strain ZUM 2407 (FORL), which causes tomato foot and root rot. In vitro and in vivo assays demonstrated antagonistic activity of strain B49b against FORL and biocontrol of tomato foot and root rot.

The B49b strain was characterised for abilities that might play a role in its biocontrol activity like protease and lactonase secretion, motility and production of antifungal metabolites. TLC and HPLC analyses indicated that strain B49b is producing the antibiotics Iturin A and surfactin. In order to visualise the interaction between the B. subtilis strain and the FORL hyphae, as well as the ability to colonize the tomato roots, B. subtilis B49b was transformed with the gfp expressing plasmid pAD44-12 (Dunn and Handelsman, 1999) by electroporation.

To our knowledge, this is the first report on the successful introduction of a GFP marker gene in a undomesticated B. subtilis strain, enabling the direct observation of this promising biocontrol strain on tomato roots in situ.