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Journal ArticleDOI

Plant growth promoting rhizobacteria as biofertilizers

16 Mar 2003-Plant and Soil (Kluwer Academic Publishers)-Vol. 255, Iss: 2, pp 571-586
TL;DR: This review focuses on the known, the putative, and the speculative modes-of-action of PGPR, which include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses.
Abstract: Numerous species of soil bacteria which flourish in the rhizosphere of plants, but which may grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria). The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to exploit them commercially as biofertilizers. After an initial clarification of the term biofertilizers and the nature of associations between PGPR and plants (i.e., endophytic versus rhizospheric), this review focuses on the known, the putative, and the speculative modes-of-action of PGPR. These modes of action include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses. The combination of these modes of actions in PGPR is also addressed, as well as the challenges facing the more widespread utilization of PGPR as biofertilizers.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors discuss evidence that upon pathogen or insect attack, plants are able to recruit protective microorganisms, and enhance microbial activity to suppress pathogens in the rhizosphere.

3,228 citations

Journal ArticleDOI
TL;DR: Biocontrol strains of fluorescent pseudomonads produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors during root colonization.
Abstract: Particular bacterial strains in certain natural environments prevent infectious diseases of plant roots. How these bacteria achieve this protection from pathogenic fungi has been analysed in detail in biocontrol strains of fluorescent pseudomonads. During root colonization, these bacteria produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, biocontrol bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels.

2,263 citations

Journal ArticleDOI
TL;DR: The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.
Abstract: Plant growth-promoting rhizobacteria (PGPR) are the rhizosphere bacteria that can enhance plant growth by a wide variety of mechanisms like phosphate solubilization, siderophore production, biological nitrogen fixation, rhizosphere engineering, production of 1-Aminocyclopropane-1-carboxylate deaminase (ACC), quorum sensing (QS) signal interference and inhibition of biofilm formation, phytohormone production, exhibiting antifungal activity, production of volatile organic compounds (VOCs), induction of systemic resistance, promoting beneficial plant-microbe symbioses, interference with pathogen toxin production etc. The potentiality of PGPR in agriculture is steadily increased as it offers an attractive way to replace the use of chemical fertilizers, pesticides and other supplements. Growth promoting substances are likely to be produced in large quantities by these rhizosphere microorganisms that influence indirectly on the overall morphology of the plants. Recent progress in our understanding on the diversity of PGPR in the rhizosphere along with their colonization ability and mechanism of action should facilitate their application as a reliable component in the management of sustainable agricultural system. The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.

1,941 citations


Cites background from "Plant growth promoting rhizobacteri..."

  • ...Best examples can be cited from legume-rhizobia symbioses in leguminous plants (Vessey 2003)....

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  • ...In some PGPR species, plant growth promotion dominates with nitrogen fixation, phosphate solubilization and production of phytohormones like auxin and cytokinin and volatile growth stimulants such as ethylene and 2, 3-butanediol (Ryu et al. 2003; Vessey 2003)....

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  • ...The concept of PGPR has now been confined to the bacterial strains that can fulfil at least two of the three criteria such as aggressive colonization, plant growth stimulation and biocontrol (Weller et al. 2002; Vessey 2003)....

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  • ...Allorhizobium, Azorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium are reported as the potent PGPR strains for their ability to act as biofertilizers (Vessey 2003)....

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  • ...A similar investigation on rhizobia to replace the use of nitrogen fertilizer was made by Vessey (2003) and thereby demonstrated a clear picture of improvement in crop yield after the inoculation of rhizobacteria in agricultural soil....

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Journal ArticleDOI
TL;DR: The main functions of rhizosphere microorganisms and how they impact on health and disease are reviewed and several strategies to redirect or reshape the rhizospheric microbiome in favor of microorganisms that are beneficial to plant growth and health are highlighted.
Abstract: Microbial communities play a pivotal role in the functioning of plants by influencing their physiology and development. While many members of the rhizosphere microbiome are beneficial to plant growth, also plant pathogenic microorganisms colonize the rhizosphere striving to break through the protective microbial shield and to overcome the innate plant defense mechanisms in order to cause disease. A third group of microorganisms that can be found in the rhizosphere are the true and opportunistic human pathogenic bacteria, which can be carried on or in plant tissue and may cause disease when introduced into debilitated humans. Although the importance of the rhizosphere microbiome for plant growth has been widely recognized, for the vast majority of rhizosphere microorganisms no knowledge exists. To enhance plant growth and health, it is essential to know which microorganism is present in the rhizosphere microbiome and what they are doing. Here, we review the main functions of rhizosphere microorganisms and how they impact on health and disease. We discuss the mechanisms involved in the multitrophic interactions and chemical dialogues that occur in the rhizosphere. Finally, we highlight several strategies to redirect or reshape the rhizosphere microbiome in favor of microorganisms that are beneficial to plant growth and health.

1,752 citations

Journal ArticleDOI
TL;DR: The latest paradigms of applicability of these beneficial rhizobacteria in different agro-ecosystems have been presented comprehensively under both normal and stress conditions to highlight the recent trends with the aim to develop future insights.

1,630 citations


Cites background from "Plant growth promoting rhizobacteri..."

  • ...Furthermore, in most studied cases, a single PGPR will often reveal multiple modes of action including bio- logical control (Kloepper, 2003; Vessey, 2003)....

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  • ...Furthermore, in most studied cases, a single PGPR will often reveal multiple modes of action including biological control (Kloepper, 2003; Vessey, 2003)....

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  • ...In accordance with Vessey (2003), soil bacterial species burgeoning in plant rhizosphere which grow in, on, or around plant tissues stimulate plant growth by a plethora of mechanisms are collectively known as PGPR (plant growth promoting rhizobacteria)....

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References
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Journal ArticleDOI
TL;DR: Genetic manipulation of phosphate-solubilizing bacteria to improve their ability to improve plant growth may include cloning genes involved in both mineral and organic phosphate solubilization, followed by their expression in selected rhizobacterial strains.

2,761 citations


"Plant growth promoting rhizobacteri..." refers background in this paper

  • ...There is ample evidence that the mode of action of many PGPR is by increasing the availability of nutrients for the plant in the rhizosphere (Glick, 1995; Rodriguez and Fraga, 1999)....

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  • ...PGPR that increase the availability of nutrients in the rhizosphere There is ample evidence that the mode of action of many PGPR is by increasing the availability of nutrients for the plant in the rhizosphere (Glick, 1995; Rodriguez and Fraga, 1999)....

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Journal ArticleDOI
TL;DR: The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed and the possibility of improving plant growth promotion by specific genetic manipulation is critically examined.
Abstract: The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed. Both indirect and direct mechanisms of plant growth promotion are dealt with. Th...

2,529 citations


"Plant growth promoting rhizobacteri..." refers background in this paper

  • ...While some believe that there contribution of these siderophores to the overall iron requirements of plants is small (Glick, 1995), other suggest an important role (Duijff et al., 1994), even a vital role, especially in calcareous soils (Masalha et al., 2000)....

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  • ...PGPR that increase the availability of nutrients in the rhizosphere There is ample evidence that the mode of action of many PGPR is by increasing the availability of nutrients for the plant in the rhizosphere (Glick, 1995; Rodriguez and Fraga, 1999)....

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Journal ArticleDOI
TL;DR: Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocOntrol agents used singly.
Abstract: The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root. Generally, saproptrophs or biotrophs such as mycorrhizal fungi grow in the rhizosphere in response to this carbon loss, but plant pathogens may also develop and infect a susceptible host, resulting in disease. This review examines the microbial interactions that can take place in the rhizosphere and that are involved in biological disease control. The interactions of bacteria used as biocontrol agents of bacterial and fungal plant pathogens, and fungi used as biocontrol agents of protozoan, bacterial and fungal plant pathogens are considered. Whenever possible, modes of action involved in each type of interaction are assessed with particular emphasis on antibiosis, competition, parasitism, and induced resistance. The significance of plant growth promotion and rhizosphere competence in biocontrol is also considered. Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocontrol agents used singly. The extreme complexity of interactions that can occur in the rhizosphere is highlighted and some potential areas for future research in this area are discussed briefly.

1,818 citations


"Plant growth promoting rhizobacteri..." refers background in this paper

  • ...Although the action of biopesticidal PGPR is often an antogonistic effect on fungal pathogens of plants (Whipps, 2001), biofertilizing PGPR sometimes enhance plant growth indirectly by stimulating the relationship between the host plant and beneficial rhizospheric fungi such as arbuscular…...

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  • ...Many PGPR stimulate the growth of plants by helping to control pathogenic organism (for reviews of PGPR as biocontrol agents see, Whipps, 2001; Zehnder et al., 2001)....

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Journal ArticleDOI
TL;DR: Soil fertility and fertilizers, Soil fertility, fertilizers and soil fertility and fertility, this paper, soil fertility, soil fertility, fertility, and fertilization, etc.
Abstract: Soil fertility and fertilizers , Soil fertility and fertilizers , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

1,776 citations

Journal ArticleDOI
TL;DR: It is argued that the simplest explanation for the observed biological activity of plant growth promoting rhizobacteria relates to the relative amounts of 1-aminocyclopropane-1-carboxylate deaminase and 1-amino-2-car boxylate oxidase in the system under consideration.

1,390 citations


"Plant growth promoting rhizobacteri..." refers background in this paper

  • ...Glick et al. (1998) put forward the theory that the mode of action of some PGPR was the production of 1-aminocyclopropane1-carboxylate (ACC) deaminase, an enzyme which could cleave ACC, the immediate precursor to ethylene in the biosynthetic pathway for ethylene in plants....

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