Author
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Kremer, Robert |
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Submitted to: Allelopathy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/28/2012 Publication Date: 1/7/2013 Citation: Kremer, R.J. 2013. Interactions between plants and microorganisms. Allelopathy Journal. 31(1):50-71. Interpretive Summary: The complete definition of allelopathy is the addition of chemicals to the environment by plants and microorganisms that have detrimental effects on the growth of neighboring plants or microorganisms. The great majority of allelopathy research has focused on effects of allelopathic plants on growth of other plants; very little work has considered environmental microorganisms as allelopathic agents. The lack of research emphasis in this area is largely due to the general inclusion of microorganisms that cause phytotoxic or allelopathic effects on plant with phytopathogens. However, allelopathic microorganisms are grouped separately from typical phytopathogens because they do not follow classical disease cycles involving aggressive infection and colonization of plant tissues. Allelopathic microorganisms passively suppress or inhibit plant root growth through production of a variety of phytotoxic compounds, or allelochemicals, absorbed by the plant, or they compete for limited plant-available nutrients in the rhizosphere (root zone). Allelopathic microorganisms comprise rhizobacteria and fungi that colonize the surfaces of plant roots and, through release of allelochemicals, detrimentally affect growth of their host plants. Thus it is important to understand the effects of allelopathic microorganisms on plant growth and discern these from traditional phytopathogens so that appropriate management of plant growth problems can be implemented based on this knowledge. The purpose of this chapter is to provide basic information on protocol development of bioassays to identify allelopathic microorganisms associated with plants. General procedures are presented as templates for devising custom protocols toward the development of standardized bioassays needed for consistent detection and characterization of allelopathic microorganisms. This chapter and the book in which it will appear is intended for use by graduate students or researchers new to the allelopathy field, in both developed and least developed countries; however, it should also serve as a valuable resource to scientists of various levels of expertise, crops extension personnel, and farmers. The opportunity for improved bioassays based on the information provided in this chapter will greatly help in better understanding the role of allelopathic microorganisms in affecting plant growth; lead to development of management practices targeted at this group of microorganisms rather than broad approaches aimed at soilborne phytopathogens in general; and yield insight on the potential of allelopathic microorganisms as weed growth-suppressing agents. Technical Abstract: Allelopathic microorganisms comprise rhizobacteria and fungi that colonize the surfaces of plant roots, and produce and release phytotoxic metabolites, similar to allelochemicals, that detrimentally affect growth of their host plants. The allelopathic microorganisms are grouped separately from typical phytopathogens because they do not follow classical disease cycles involving aggressive infection and colonization of plant tissues. Allelopathic microorganisms passively suppress or inhibit plant root growth through production of a variety of phytotoxic compounds absorbed by the plant, or they compete for limited plant-available nutrients in the rhizosphere. Thus it is important to understand the effects of allelopathic microorganisms on plant growth and discern these from traditional phytopathogens so that appropriate management of plant growth problems can be implemented based on this knowledge. The purpose of this chapter is to provide basic information on protocol development of bioassays to identify allelopathic microorganisms associated with plants. Guidance provided by the general procedures offered as templates for devising custom protocols should aid in eventual development of standardized bioassays for consistent detection and characterization of allelopathic microorganisms, for which little information and reliable data currently exist. The use of improved bioassays that yield reproducible results will enhance comprehension of effects of allelopathic microorganisms on plant growth and increase the overall perspective of functional biology and ecology of the rhizosphere microbial community beyond that limited to interactions of plants and soilborne phytopathogens. |
