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United States Department of Agriculture

Agricultural Research Service

Title: Bacterial Endophytes in Agricultural Crops

Authors
item Hallmann, J - ALABAMA AG. EXPT. STN.
item Quadt-Hallmann, A - ALABAMA AG. EXPT. STN.
item Mahaffee, Walter
item Kloepper, J - ALABAMA AG. EXPT. STN.

Submitted to: Canadian Journal of Microbiology
Publication Type: Review Article
Publication Acceptance Date: July 15, 1997
Publication Date: N/A

Interpretive Summary: Bacteria that colonize internal plant tissues (endophytic bacteria) are ubiquitous in most plant species, residing latently or actively colonizing the plant locally as well as systemically. Historically these bacteria have been thought to be weakly virulent plant pathogens, but have recently been discovered to have several beneficial effects on host plants, such as growth promotion and increased resistance against plant pathogens and parasites. In general, endophytic bacteria originate from the epiphytic bacterial communities of the root or leaf surface as well as from seed or planting materials. Endophytic bacteria occur at lower population densities than pathogens and, at least some of them, do not induce a hypersensitive response in the plant which indicates that they are not recognized by the plant as pathogens. Overall, the internal microflora of plants is dynamic in structure and influenced by biotic and abiotic factors, with the plant itself constituting one of the major influencing factors. This review summarizes part of the work being done on endophytic bacteria, including their colonization and establishment in the host plant as well as their role in plant-microbe interactions.

Technical Abstract: Endophytic bacteria are ubiquitous in most plant species, residing latently or actively colonizing the plant tissues locally as well as systemically. Historically these endophytic bacteria have been thought to be weakly virulent plant pathogens, but have recently been discovered to have beneficial effects on host plants, such as growth promotion and increased resistance against plant pests. In general, endophytic bacteria originate from the epiphytic bacterial communities of the rhizosphere, phylloplane, seeds, and planting materials. Endophytic bacteria gain entrance into plants through natural openings or wounds,and appear to actively penetrate plant tissues using hydrolytic enzymes. In general, endophytic bacteria occur at lower population densities than pathogens and, at least some of them, do not induce a hypersensitive response in the plant which indicates that they are not recognized by the plant as pathogens. Evolutionarily, endophytes appear to be intermediate between saprophytic bacteria and plan pathogens, but it can only be speculated whether they are saprophytes evolving toward pathogens or are more highly evolved from plant pathogens which conserved protective shelter and nutrient supplies by not killing their host. The endophytic community structure is dynamic and is influenced by biotic and abiotic factors, with the plant itself constituting one of the major influencing factors. Since endophytic bacteria rely on the nutritional supply offered by the plant, any parameter affecting the nutritional status of the plant could consequently affect the endophytic community. This review summarized part of the work being done on endophytic bacteria, including their colonization and establishment in the host plant as well as their role in plant-microbe interactions.

Last Modified: 12/19/2014
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