|Sarwar, Muhammad - UNIV OF MO|
Submitted to: Proceedings of Plant Growth Regulation Society of America
Publication Type: Proceedings
Publication Acceptance Date: July 18, 1995
Publication Date: N/A
Technical Abstract: Weed management strategies that exploit microorganisms for weed control have developed to potentially reduce the widespread use of herbicides in agroecosystems. Microorganisms that specifically inhibit the growth of weed seedlings may hinder the establishment of weed populations competing with crops for growth requirements. Among the most promising agents for weed seedling inhibition are deleterious rhizobacteria (DRB), which aggressively colonize and establish on seedling roots. DRB were examined for their ability to produce phytotoxic metabolites in the weed seedling rhizosphere and for host specificity of the metabolites. Inocula of DRB previously selected for phytotoxicity in agar bioassays were applied to soil planted to soybean (Glycine max) and green foxtail (Setaria viridis). Half the inoculated treatments received precursor compounds for enhanced metabolite production. Growth parameters of both plant species were determined and soils were analyzed by HPLC for metabolite production. Roo growth of green foxtail was greatly suppressed by Enterobacter taylorae when applied with tryptophan, but root growth of soybean was not affected. HPLC analyses revealed production of high concentrations of indole-3-acetic acid and tryptophol. Excessive concentrations of auxins can be detrimental to plant growth and may be factors involved in DRB effects on weed seedling growth. Use of rhizobacteria specifically detrimental toward weed seedling growth partially through phytotoxins could minimize weed competition and reduce use of herbicides in agroecosystems.