Host range of a deleterious rhizobacterium for biological control of downy brome

Abstract Pseudomonas fluorescens strain D7 (P. f. D7; NRRL B-18293) is a root-colonizing bacterium that inhibits downy brome (Bromus tectorum L. BROTE) growth. Before commercialization as a biological control agent, strain D7 must be tested for host plant specificity. Agar plate bioassays in the laboratory and plant–soil bioassays in a growth chamber were used to determine the influence of P. f. D7 on germination and root growth of 42 selected weed, cultivated or native plant species common in the western and midwestern United States. In the agar plate bioassay, all accessions of downy brome were inhibited by P. f. D7. Root growth of seven Bromus spp. was inhibited an average of 87% compared with that of controls in the agar plate bioassay. Root growth of non-Bromus monocots was reduced by 0 to 86%, and only 6 out of 17 plant species were inhibited 40% or greater. Among all plant species, only downy brome root growth from two accessions was significantly inhibited by P. f. D7 in plant–soil bioassays (42 and 64%). P. f. D7 inhibited root growth and germination in agar plate bioassays more than in plant–soil bioassays. Inhibition in plant–soil bioassays was limited to downy brome, indicating promise for P. f. D7 as a biocontrol agent that will not harm nontarget species. Nomenclature: Downy brome; Bromus tectorum L. BROTE; rhizobacterium; Pseudomonas fluorescens.

[1]  A. Caesar,et al.  Effects of European and U.S. Strains of Fusarium spp. Pathogenic to Leafy Spurge on North American Grasses and Cultivated Species , 1999 .

[2]  D. Sands,et al.  Isolation of fluorescent pseudomonads with a selective medium. , 1970, Applied microbiology.

[3]  S. Levy,et al.  Survival of rifampin-resistant mutants of Pseudomonas fluorescens and Pseudomonas putida in soil systems. , 1988, Applied and environmental microbiology.

[4]  J. Kloepper,et al.  Colonization of soybean roots by Pseudomonas and Serratia species: relationship to bacterial motility, chemotaxis, and generation time , 1988 .

[5]  A. DiTommaso,et al.  Susceptibility of Various Accessions ofConvolvulus arvensistoPhomopsis convolvulus , 1999 .

[6]  J. Lynch,et al.  MICROBIAL EFFECTS ON THE GERMINATION AND SEEDLING GROWTH OF BARLEY , 1980 .

[7]  M. Julien,et al.  The Host Range ofEccritotarsus catarinensis(Heteroptera: Miridae), a Potential Agent for the Biological Control of Waterhyacinth (Eichhornia crassipes) , 1999 .

[8]  T. Suslow.  Role of deleterious rhizobacteria as minor pathogens in reducing crop growth. , 1982 .

[9]  J. Kloepper.  Relationship of in vitro Antibiosis of Plant Growth-Promoting Rhizobacteria to Plant Growth and the Displacement of Root Microflora , 1981 .

[10]  R. H. Callihan,et al.  The Biology of Downy Brome (Bromus tectorum) , 1984, Weed Science.

[11]  A. Wapshere.  A strategy for evaluating the safety of organisms for biological weed control , 1974 .

[12]  A. C. Kennedy,et al.  Metabolites from Pseudomonas fluorescens Strain D7 Inhibit Downy Brome (Bromus tectorum) Seedling Growth , 1996, Weed Technology.

[13]  R. Peer,et al.  Plant growth responses to bacterization with selected Pseudomonas spp. strains and rhizosphere microbial development in hydroponic cultures , 1989 .

[14]  A. C. Kennedy,et al.  Rhizobacteria as Biocontrol Agents of Weeds , 1996, Weed Technology.

[15]  D. TeBeest,et al.  Mycoherbicides: progress in the biological control of weeds , 1985 .

[16]  T. Peeper.  Chemical and Biological Control of Downy Brome (Bromus tectorum) in Wheat and Alfalfa in North America , 1984, Weed Science.

[17]  K. Domsch,et al.  Decomposition of 14C- and 15N-labelled microbial cells in soil , 1982 .

[18]  A. C. Kennedy,et al.  Isolation and Characterization of Metabolites from Pseudomonas fluorescens-D7 for Control of Downy Brome (Bromus tectorum) , 1994, Weed Science.

[19]  C. L. Douglas,et al.  Rhizobacteria Suppressive to the Weed Downy Brome , 1991 .

[20]  P. Tranel,et al.  Inhibition of Downy Brome (Bromus tectorum) Root Growth by a Phytotoxin from Pseudomonas fluorescens Strain D7 , 1993, Weed technology.

[21]  L. A. Morrow,et al.  The History and Distribution of Downy Brome (Bromus tectorum) in North America , 1984, Weed Science.

[22]  Susan M. Boyetchko,et al.  Principles of Biological Weed Control with Microorganisms , 1997 .

[23]  C. Haack,et al.  Population Dynamics of Soil Pseudomonads in the Rhizosphere of Potato (Solanum tuberosum L.) , 1985, Applied and environmental microbiology.

[24]  A. C. Kennedy,et al.  Microorganisms in Weed Control Strategies , 1996 .