Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 4, 2014
Publication Date: N/A
Interpretive Summary: Endophytic microorganisms are those that dwell within plants and confer some positive benefits including disease suppression, insect resistance, and environment stress relief as drought and temperature tolerances. Since all plants are naturally infected with endophytes their use in agricultural crop plants for biological improvements are anticipated. The authors of this paper were invited to review and comment on the present and future status of bacterial endophytes as biocontrol agents for future and present uses in crop improvements. This work highlights the major genus of bacteria used for biocontrol: Bacillus. However, as an example of this genus, this chapter highlights studies done at the Russell Research Center with the patented bacterium Bacillus mojavensis and its control of a major toxic endophytic fungus Fusarium verticillioides. This fungus produces several types of mycotoxins (the fumonisins). This chapter served to address both the diversity of chemicals produced by Bacillus species and the specific utilization of endophytic species, especially B. mojavensis, as biocontrol organisms. It addressed evidence for their impact on alleviating plant stresses, both abiotic and biotic with suggestions on future studies necessary for specific mechanisms that may assist in increasing their performance as biocontrol agents in crop plants.
Technical Abstract: Knowledge of endophytic bacteria and their potential for protecting crops has targeted the endophytic species of Bacillus as a valued microorganism not only for disease protection but also for inducing plant defense mechanisms. Numerous strains of Bacillus, endophytic and non-endophytic, are widely being used to stimulate plant growth, stimulate plants immune system, and to suppress soil-borne and foliage infecting diseases. Bacillus species and its endophytic strains are also used for a wide range of antibiotics that inhibit pathogens directly on cellular structures or at the molecular and physiological levels. The endophytic species and strains produce fungal inhibitory compounds that belong to three broad families of lipopeptides and these include the bacillomycins, fengycins, and surfactins. Bacilli also produce the ribosomal synthesized antimicrobial peptides bacteriocins, which have been implemented in plant protection schemes to control fungal and bacterial diseases. Others have yet to be identified. These compounds form the basis of intense activity ranging from acute toxicity to serving as signal transduction systems for specific cellular functions, organelle formation, and responses to environmental changes and challenges. This review serves to address both the diversity of chemicals produced by Bacillus species and the specific utilization of endophytic species, especially B. mojavensis, as biocontrol organisms. It will address some evidence for their impact on alleviating plant stresses, both abiotic and biotic with suggestions on future studies necessary for specific mechanisms that may assist in increasing their performance as biocontrol agents.