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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #221658

Title: Germination-Arrest Factor (GAF): Biological properties of a novel, naturally-occurring herbicide produced by selected isolates of rhizosphere bacteria

item Banowetz, Gary
item Azevedo, Mark

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2008
Publication Date: 4/29/2008
Citation: Banowetz, G.M., Azevedo, M.D., Armstrong, D.J., Halgren, A.B., Mills, D.I. 2008. Germination-Arrest Factor (GAF): Biological properties of a novel, naturally-occurring herbicide produced by selected isolates of rhizosphere bacteria. Biological Control.46:380-390.

Interpretive Summary: A selection of bacteria isolated from soils in Western Oregon were shown to produce a substance that arrests the germination of many weed seeds that are problems in crop production in the Pacific Northwest. One of the weeds is annual bluegrass, a plant that contaminates grass seed shipments destined for global markets. There is potential for utilizing the substance produced by these bacteria in some form of biological control to prevent germination of weed seeds and their subsequent contamination of grass seed shipments.

Technical Abstract: Five strains of Deleterious Rhizosphere Bacteria (DRB), identified as Pseudomonas fluorescens, were shown to produce and secrete a naturally-occurring herbicide that targets the seeds of certain graminaceous plants, including annual bluegrass (ABG; Poa annua L.), considered a weed in many agronomic systems. The herbicide arrests germination of the seeds in a developmentally specific manner, typically irreversibly blocking the germination process immediately after the emergence of the plumule and coleorhiza. Because of its unique mode of action, this herbicide has been termed a Germination-Arrest Factor (GAF). Bacterial culture filtrates containing GAF arrest seed germination of a large number of graminaceous species, including noxious grassy weeds and grass species grown for seed and food. The germination of corn seeds did not appear to be affected by the herbicide. The seeds of dicot species appear to be less sensitive to GAF than seeds of graminaceous species. The biological effects of GAF on graminaceous species is primarily limited to germination, although transient slowing of ABG seedling growth was observed after post-germination exposure to GAF. Exposure of non-germinated ABG seeds to GAF for periods as short as 20 hours was sufficient to irreversibly arrest germination. A quantitative bioassay for GAF was developed based on the sensitivity of ABG seed to this compound.