Abstract
The impact of allelopathic, nonpathogenic bacteria on plant growth in natural and agricultural ecosystems is discussed. In some natural ecosystems, evidence supports the view that in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals. In agricultural ecosystems allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals. Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease. Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils. Evaluation of phytotoxic activity under controlled conditions, as well as ways to apply allelopathic bacteria in the field, is approached. The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s) or indirectly through the suppression of an essential symbiont. The process is affected by nutritional and other environmental conditions, some may control bacterial density and the rate of production of allelochemicals. Allelopathic nonpathogenic bacteria include a wide range of genera and secrete a diverse group of plant growth-mediating allelochemicals. Although a limited number of plant growth-promoting bacterial allelochemicals have been identified, a considerable number of highly diversified growth-inhibiting allelochemicals have been isolated and characterized. Some species may produce more than one allelochemical; for example, three different phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolated from Streptomyces hygroscopicus. Efforts to introduce naturally produced allelochemicals as plant growth-regulating agents in agriculture have yielded two commercial herbicides, phosphinothricin, a product of Streptomyces viridochromogenes, and bialaphos from S. hygroscopicus. Many species of allelopathic bacteria that affect growth of higher plants are not plant specific, but some do exhibit specificity; for example, dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons. Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce. Therefore, when test plants are employed to evaluate bacterial allelopathy, final evaluation must include those species that are assumed to be suppressed in nature. The release of allelochemicals from plant residues in plots of ‘continuous crop cultivation’ or from allelopathic living plants may induce the development of specific allelopathic bacteria. Both the rate by which a bacterium gains from its allelopathic activity through utilizing plant excretions, and the reasons for the developing of allelopathic bacteria in such habitats, are important goals for further research.
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Claims 13
Claim · model-written summary
Phytotoxic microorganisms can amplify retardation of annual plants near allelopathic perennials.
Verbatim
e0“in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals.”
Claim · model-written summary
Successive single-crop cultivation can be associated with allelopathic bacteria and yield decline uncorrected by minerals.
Verbatim
e0“In agricultural ecosystems allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals.”
Claim · model-written summary
Transfer of suppression-area soils induced crop retardation in unaffected areas.
Verbatim
e0“Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease.”
Claim · model-written summary
Higher-plant susceptibility to deleterious rhizobacteria is often seen in sandy or skeletal soils.
- Taxon
- higher plantsEmbryophytae0
- Interactor
- deleterious rhizobacteriae0other
- Outcome
- Susceptibility of higher plantse0
- Setting
- sandy or so-called skeletal soilse0
Not reportedDirection
Verbatim
e0“Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils.”
Claim · model-written summary
Bacterial allelochemicals may directly affect susceptible plants.
Verbatim
e0“The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s)”
Claim · model-written summary
Bacteria may act indirectly by suppressing an essential symbiont.
Verbatim
e0“or indirectly through the suppression of an essential symbiont.”
e1“susceptible plant(s)”
Claim · model-written summary
Diverse growth-inhibiting allelochemicals have been isolated and characterized.
- Taxon
- higher plantsEmbryophytae1
- Outcome
- growth-inhibiting allelochemicals have been isolated and characterizede0
Verbatim
e0“a considerable number of highly diversified growth-inhibiting allelochemicals have been isolated and characterized.”
e1“Many species of allelopathic bacteria that affect growth of higher plants”
Claim · model-written summary
Streptomyces hygroscopicus yielded geldanamycin, nigericin and hydanthocidin.
- Taxon
- higher plantsEmbryophytae1
- Interactor
- Streptomyces hygroscopicus
Streptomyces hygroscopicuse0other - Outcome
- phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“three different phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolated from Streptomyces hygroscopicus.”
e1“Many species of allelopathic bacteria that affect growth of higher plants”
Claim · model-written summary
Naturally produced bacterial allelochemicals yielded two commercial herbicides.
- Taxon
- higher plantsEmbryophytae1
- Outcome
- two commercial herbicidese0
- Value
- twoe0
Verbatim
e0“Efforts to introduce naturally produced allelochemicals as plant growth-regulating agents in agriculture have yielded two commercial herbicides, phosphinothricin, a product of Streptomyces viridochromogenes, and bialaphos from S. hygroscopicus.”
e1“Many species of allelopathic bacteria that affect growth of higher plants”
Claim · model-written summary
Dicotyledonous plants were more susceptible to Pseudomonas putida than monocotyledons.
- Taxon
- dicotyledonous plantse0
- Interactor
- Pseudomonas putida
Pseudomonas putidae0other - Outcome
- susceptible to Pseudomonas putidae0
- Direction
- more susceptiblee0
- Comparator
- monocotyledonse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons.”
Claim · model-written summary
Cultivars of wheat differed in susceptibility to allelopathic bacteria.
- Taxon
- wheat
Triticum aestivume0 - Interactor
- allelopathic bacteriae0other
- Outcome
- Differential susceptibilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce.”
Claim · model-written summary
Cultivars of lettuce differed in susceptibility to allelopathic bacteria.
- Taxon
- lettuce
Lactuca sativae0 - Interactor
- allelopathic bacteriae0other
- Outcome
- Differential susceptibilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce.”
Claim · model-written summary
Tests of bacterial allelopathy should include species expected to be suppressed in nature.
Verbatim
e0“when test plants are employed to evaluate bacterial allelopathy, final evaluation must include those species that are assumed to be suppressed in nature.”