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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #118437
Title: CYANIDE PRODUCTION BY RHIZOBACTERIA AND POTENTIAL FOR SUPPRESSION OF WEED SEEDLING GROWTH

Author
item Kremer, Robert
item SOUISSI, THOURAYA - INST NAT AGRON DE TUNISIE

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2001
Publication Date: 6/1/2001
Citation: Kremer, R.J., Souissi, T. 2001. Cyanide production by rhizobacteria and potential for suppression of weed seedling growth. Current Microbiology. 43:182-186.

Interpretive Summary: The soil and plant root rhizosphere environments are habitats for multitudes of microorganisms, many of which produce a variety of natural chemical compounds with potential benefits for agriculture. We surveyed a group of root-inhabiting bacteria, rhizobacteria, for their ability to produce chemicals that are detrimental to the growth of weeds that infest many crops. About one-third of the rhizobacteria tested produced the toxi compound hydrogen cyanide (HCN). HCN becomes toxic to plants when concentrated in soil pores around roots where the producing bacteria live. We found that cyanide-producing rhizobacteria greatly reduced root growth of foxtail, bindweed, and barnyardgrass--some of our most economically important weeds. Results of this study are important to scientists and producers because these rhizobacteria can be exploited as a biological control method for weeds. Also, it may be possible to entice soil bacteria to produce HCN specifically targeted toward emerging weed seedlings prior to planting a crop. Using this approach, weed infestations may be reduced effectively with limited reliance on herbicides and minimal adverse effects on the environment.

Technical Abstract: Rhizobacteria strains were characterized for their ability to synthesize hydrogen cyanide and for effects on seedling root growth of various plants. Approximately 32% of bacteria from a collection of over 2000 isolates were cyanogenic, evolving HCN from trace concentrations to > 30 nmoles/mg cellular protein. Cyanogenesis was predominantly associated with pseudomonads and was enhanced when glycine was provided in the culture medium. Concentrations of HCN produced by rhizobacteria were similar to exogenous concentrations inhibiting seedling growth in bioassays, suggesting that cyanogenesis by rhizobacteria in the rhizosphere can adversely affect plant growth. Growth inhibition of lettuce and barnyardgrass by volatile metabolites of the cyanogenic rhizobacteria confirmed that HCN was the major inhibitory compound produced. Our results suggest that HCN produced in the rhizospheres of seedlings by selected rhizobacteria is a potential and environmentally compatible mechanism for biological control of weeds.