Research and Extension1 and USDA-ARS-GRL2, Langston University, P.O. Box 1730, Langston, OK, 73050 USA.
The potential of rhizobacteria in enhancing crop productivity is no longer questioned. Allelopathic rhizobacteria offer opportunity for enhancement of sustainable agriculture and their role in crop production and protection is reviewed here. Introduced allelopathic rhizobacteria promote plant growth by producing phytohormones in the soil or within the inoculated plant, by seedling growth stimulation, by acceleration of mineralization and uptake of nutrients, and by the enhancement of nitrogen fixation or mycorrhizal growth. Other research has shown the efficacy of rhizobacteria for weed control. For example, two pseudomonad isolates suppressed the growth of a natural infestation of Bromus tectorum in wheat by more than 50%. In this case phenazine-1-carboxylic acid was implicated as the major phytotoxin causing the weed suppression. In an other example, bacterial metabolites suppressed Phleum pratense and Trifolium pratense in barley. Rhizobacteria that control plant disease can also contribute to sustainable agriculture. Disease control is achieved by antibiosis, by production of enzymes or cyanamide, or by induction of systemic disease resistance in the host plant. A better understanding of the microbial ecology in the root zone and the interaction between the introduced bacteria and the host plant is necessary if selected microorganisms are to have an extensive role in sustainable agriculture.
Rhizobacteria can enhance crop productivity by promoting plant growth through production of phytohormones,increasing access to nutrients, enhancing nitrogen fixation or controlling weeds.
Allelopathy, Bacterial metabolites, phytohormones, rhizobacteria,