ABSTRACT
Microorganisms can significantly influence the distribution, abundance, and competition among plant species, and thus they can be used in biological weed control programs. Deleterious rhizobacteria (DRB) are soil bacteria that colonize the rhizosphere and suppress plant growth by the production of phytotoxic substances. Awareness of the ecological constraints of the pathogen and the weed is critical to successful biological weed control. The DRB and the grass weed downy brome make a good match as a biological control system because the bacteria suppress weed growth at a point in the weed life cycle that reduces its competitiveness with the crop. Investigations should include a wide range of microorganisms, both fungi and bacteria, to develop a variety of candidates and hosts for biological control of broadleaf and grass weeds. Molecular investigations of DRB will uncover the genetic basis of virulence and host specificity and broaden our appreciation of the range of diversity in pathogens.
