Pseudomonas sp. strain MF30 suppresses Fusarium wilt of tomato in vivo

In a search of bacterial biological control agents, 50 bacterial isolates collected from roots of wild plants in northern Sweden were tested in vivo for suppression of wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici. Tomato plants were sown in 10-cm-diam. pots and after 21 d 7 ml of bacterial suspension (ca. 2x109 cfu ml-1) was poured into the soil around each plant. Two days later, 10 ml of pathogen suspension was soil-inoculated (106 conidia ml-1) around the same plants. After a further 20 days, disease incidence was measured. One bacterial isolate, MF30, protected plants from Fusarium wilt, even though the fungal pathogen and not MF30 actually colonized the plant. Several mechanisms may have contributed to the suppression of Fusarium wilt, including systemic induced resistance. The MF30 strain is highly similar to members of the RNA group I of the Pseudomonas fluorescens, well known for its capacity to induce systemic resistance.