|Samac, Deborah - USDA, ARS, ST. PAUL, MN|
Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 2003
Publication Date: May 1, 2003
Citation: Burelle, N.K., Samac, D.A. 2003. Use of gram-positive bacteria as biological control agents for plant parasitic nematodes. Journal of Nematology. 35:347-348. Interpretive Summary: Two types of bacteria with potential for commercial development as biological control agents for plant parasitic nematodes are plant growth-promoting rhizobacteria (PGPR) and species of Streptomyces. A PGPR formulation that has been shown to improve plant vigor, reduce disease severity and increase yield of tomato, pepper, muskmelon and watermelon in Florida is available as BioYieldTM. Streptomyces spp. are well known to be important components of disease suppressive soils, and certain species produce potent nematicidal chemical compounds known as avermectins, which have been formulated into many commercial nematicides and insecticides. Current research results on use of these types of bacteria for plant parasitic nematode control will be discussed in this Biological Control Symposium presentation at the annual meeting for the Society of Nematologists.
Technical Abstract: Gram-positive bacteria are well-suited for development as biological control agents for plant parasitic nematodes because many are easy to culture, produce a wide array of chemical compounds, and form spores that enable drying and storage of formulations. Two types of gram-positive bacteria with potentially different modes of action will be discussed. The first type is plant growth-promoting rhizobacteria (PGPR). Numerous PGPR are gram-positive bacteria, and of these, many are Bacillus spp. Mechanisms for disease reduction with PGPR are primarily considered to be indirect. PGPR often induce systemic resistance or increase tolerance to pathogens in the host plant, resulting in increased plant growth and yield. In Florida field trials, two gram-positive PGPR isolates (Bacillus subtilis strain GBO3 and B. amyloliquifaciens strain IN937a) in a formulation containing chitin, reduced root-knot nematode (Meloidogyne incognita) galling and improved root condition of pepper (Capsicum anuum) and muskmelon (Cucumis melo) when added to transplant media at seeding. A second type of gram-positive bacteria with biological control activity against nematodes is Streptomyces. Streptomyces spp. have been isolated from many disease suppressive soils and some exhibit direct antagonism of plant parasitic nematodes through the production of antihelminthic compounds such as macrocyclic lactones. Several isolates of Streptomyces previously shown to suppress potato scab disease (Streptomyces scabies) in the field were shown to also reduce populations of root lesion nematodes (Pratylenchus penetrans) in both susceptible and resistant alfalfa (Medicago sativa) varieties. Studies are underway to evaluate the effects of these Streptomyces isolates on root-knot nematode populations and to determine if they also induce systemic resistance responses in the host.