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Poster: Biology & Disease Mgmt: Biological Control


Evaluation of potential biocontrol agents against fungal plant pathogens affecting strawberry
R. BITTER (1), G. Holmes (2) (1) California Polytechnic State University, U.S.A.; (2) Cal Poly Strawberry Center, U.S.A.

Botrytis cinerea, Fusarium oxysporum f. sp. fragariae and Macrophomina phaseolina are important pathogens that limit commercial strawberry production in California. The objective of this study was to evaluate eight species of bacteria (19 strains) for their ability to inhibit mycelial growth of all three pathogens in vitro. Percent inhibition of fungal growth due to the presence of each bacterium was determined relative to growth in the absence of each bacterium. Three strains of Bacillus amyloliquefaciens provided the greatest inhibition of B. cinerea, F. oxysporum f. sp. fragariae and M. phaseolina by an average of 43.7%, 47.8%, 42.7%, respectively, between replications. Significant differences in fungal inhibition were observed between strains of the same bacterial species, suggesting inhibition is strain-dependent. Growth inhibition caused by five B. subtilis strains varied from 39.5% to 0.6% for B. cinerea, 43.1% to 0.6% for F. oxysporum f. sp. fragariae, and 39.8% to 5.8% for M. phaseolina. Four B. licheniformis strains also displayed similar levels of strain-dependent inhibition. Bacterial antagonists that limit the growth of these soilborne and foliar pathogens could provide an alternative to the use of chemical fumigants and fungicides, or could be utilized to enhance the effectiveness of conventional or organic disease control treatments such as anaerobic soil disinfestation.