PARENT SESSION
Poster Session #61: Soil Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Do some prairie plants enhance indigenous soil microbial antagonists to protect against disease?

DAVELOS, ANITA^*,1, KINKEL, LINDA¹, XIAO, KUN¹, RODGERS, MATTHEW¹, ¹ University of Minnesota, St. Paul, MN

ABSTRACT- Antibiotic-producing Streptomycetes have been shown to control a wide range of soilborne plant pathogens on cultivated plants, and are used as inoculants to control plant disease in agriculture. Moreover, cultivated plant species have been shown to vary in their conduciveness to colonization by Streptomycetes. Because of their potential to confer significant protection against soilborne plant pathogens, we hypothesize that some prairie plant species may selectively enrich antibiotic-producing Streptomyces as a means of disease suppression. Soilborne plant pathogens can represent a particular challenge to long-lived perennial plant species because of the inability of the plant to escape, and the potential for continual genetic change in the pathogen population. We examined the densities and antibiotic activities of the indigenous Streptomycete communities in the rhizosphere of 3 native perennial species (Andropogon gerardii, Lespedeza capitata, and Lithospermum canescens) at Cedar Creek Natural History Area in east-central Minnesota. We found that the rhizosphere density of antibiotic-producing Streptomycetes varied significantly among plant species. In addition, Streptomycete communities from the rhizosphere of different plant species varied significantly in their inhibitory activity as measured against a collection of 10 standard Streptomycete test isolates. Streptomycetes from different plant species also varied in their inhibitory activity against different soilborne pathogens (Verticillium, Fusarium, Streptomyces, and Rhizoctonia), and inhibition of particular pathogens was sometimes specific to a single Streptomycete community. These data are consistent with the hypothesis that some perennial plant species may develop protective mutualisms with soilborne bacteria in which the plants selectively enrich antibiotic-producing bacteria in the rhizosphere that are capable of providing protection against soilborne plant pathogens.

KEY WORDS: protective mutualism , microbial antagonist , plant pathogen