Various fungi and bacteria with known biocontrol activity against soilborne fungal pathogens were tested for their efficacy in controlling Fusarium wilt of tomato. Existing biocontrol strains--including commercial formulations--and potential new antagonists, isolated from on and around tomato roots (growing in field plots at the Beltsville Agricultural Research Center in Maryland), were used. The potential benefit of combining various organisms to enhance control was also investigated.
Tomato seedlings were treated with the potential biological control agents in the greenhouse and transplanted into pots containing Fusarium-infested soil. The plants were monitored for 4 to 6 weeks for disease development. Fusarium could not be isolated from asymptomatic plants, and these plants continued to remain healthy and developed normally even after the study ended. In diseased plants, symptoms worsened over time, eventually ending in plant death.
Individual isolates within all groups of the known biocontrol organisms reduced disease incidence 35-100%. As a group, the most effective antagonists were the non-pathogenic Fusarium isolates collected from wilt-suppressive soils. The French isolate Fo47, which is being developed as a biocontrol agent for Fusarium diseases in Europe, reduced disease by 50%. Several isolates originally collected from watermelon roots in Florida reduced disease by up to 100%, and were equally effective in controlling Fusarium on watermelon and muskmelon. Other organisms, including isolates of Gliocladium virens, Trichoderma hamatum, Pseudomonas fluorescens, and Burkholderia cepacia reduced disease 30-65%, but were not as consistently effective.
Biocontrol isolates that were most effective in individual assays were tested in various combinations, but did not provide significantly better control than the nonpathogenic Fusarium antagonists alone.
Larkin, R. P. and D. R. Fravel. 1998. Efficacy of various fungal and bacterial biocontrol organisms for control of Fusarium wilt of tomato. Plant Disease 82: 1022-1028.
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