Nonpathogenic Fusarium oxysporum Strain Fo47 Induces Resistance to Fusarium Wilt in Tomato.

Nonpathogenic Fusarium oxysporum strain Fo47 controls the incidence of Fusarium wilt. Four bioassays in which a strain of the pathogen F. oxysporum f. sp. lycopersici and Fo47 were not in direct contact were developed to evaluate whether Fo47 could induce resistance to Fusarium wilt in tomato plants. Fo47 and the pathogen were separated either physically or in time. Bio-assays were carried out under hydroponic conditions (two bioassays), in potting mix, or in autoclaved soil. Strain Fo47 protected tomato against Fusarium wilt in all four bioassays. Inoculation with Fo47 increased chitinase, β-1,3-glucanase, and β-1,4-glucosidase activity in plants, confirming the ability of Fo47 to induce resistance in tomato. This report is the first to demonstrate that a nonpathogenic strain of F. oxysporum can induce resistance to Fusarium wilt in tomato plants. This result has important practical implications for biocontrol of tomato diseases under commercial conditions.