Biological Control of Plant Disease
Using Antagonistic Streptomyces
Daqun Liu, Linda L. Kinkel, Eric C. Eckwall,
Neil A. Anderson, and Janet L. Schottel
Streptomyces spp. are common soil-borne microorganisms that are noted for their abilities to produce antibiotics and other secondary metabolites. About two-thirds of the naturally occurring antibiotics are produced by Streptomyces spp. and other actinomycetes ( Chater and Hopwood 1989). Streptomycetes are mainly saprophytic and utilize insoluble organic debris by producing extracellular hydrolytic enzymes such as cellulases, hemicellulases, proteases, amylases, and nucleases. They also adapt to their environments by forming hyphae that penetrate substrates and allow enzymes to be secreted with a relatively high local concentration ( Chater and Hopwood 1989).
Because of their competence in colonizing the soil and their proficiency in producing antimicrobial compounds, Streptomyces strains are attractive as potential biocontrol agents. Recently, members of this genus have been investigated for their potential to control a wide range of plant pests in a number of different systems. In our work at the University of Minnesota, Streptomyces strains have been extensively investigated in field, greenhouse, and laboratory studies for their ability to control Streptomyces scabies (causal agent of potato scab) and other plant pathogens. In addition to practical studies on biocontrol, we have focused research on the ecology, biochemistry, taxonomy, and physiology of the naturally occurring pathogen-suppressive Streptomyces strains in efforts to enhance biological control. In this chapter we will briefly survey systems in which streptomycetes have been investigated for their ability to act as biocontrol agents. Our primary focus will be to summarize the information obtained in our programs on the use of Streptomyces spp. for the biological control of potato scab.