ISHS Acta Horticulturae 504: VI Symposium on Stand Establishment and ISHS Seed Symposium
GENETIC MODIFICATIONS OF PSEUDOMONAS THAT ENHANCE BIOLOGICAL DISEASE CONTROL |
| Authors: | J.M. Ligon, D.S. Hill, P.E. Hammer, N.R. Torkewitz, D. Hofmann, H.-J. Kempf |
| Keywords: | Biocontrol, Pseudomonas, pyrrolnitrin |
| Abstract:
Pseudomonas fluorescens strain BL915 is an effective biocontrol agent for the control of plant disease caused by the damping-off pathogens Rhizoctonia and Pythium. Application of this bacterium to the seed of a wide variety of plants protects the plants from these pathogens. The biocontrol activity of this strain has been determined to be due to the production by the bacterium of antifungal metabolites and proteins, including pyrrolnitrin, alkyl resorcinol, chitinase, HCN and gelatinase. The synthesis of these compounds is coordinately regulated by a two-component bacterial regulatory system. We have cloned and characterized the genes encoding the protein components of this regulatory system. The genes encoding the biosynthesis of pyrrolnitrin have also been cloned and characterized. Genetic modifications of the regulatory genes and the pyrrolnitrin biosynthetic genes independently resulted in increased production of antifungal metabolites and pyrrolnitrin, respectively, and in a concomitant increase in biocontrol activity. Incorporation of multiple genetic modifications into single Pseudomonas strains resulted in further increases in antifungal metabolite biosynthesis and biocontrol activity. Genetically modified Pseudomonas strains have been developed that produce approximately 10-fold more pyrrolnitrin than the parent strain. These strains have been shown in greenhouse and field tests to be as effective as chemical fungicides in protecting seedlings from damping-off pathogens. | |
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