Plant Growth-Promoting Rhizobacteria: An Eco-friendly Approach for Sustainable Agroecosystem
01 Jan 2016-pp 181-201
TL;DR: This chapter focuses on various aspects and mechanisms of biocontrol of plant pathogens; plant growth promotion, commercialization of their wide applications, and future prospects of PGPR are also discussed.
Abstract: Soil-borne diseases caused by fungal and bacterial pathogens are a major threat to crop and its yield. These diseases significantly reduce the crop yield and lead to the production of micronutrient deficient staple crops. Consumption of these staple crops or food has been the main cause of many micronutrient deficiency disorders in human beings, for instance, iron deficiency anemia (IDA) caused due to iron deficiency. Frequent use of chemical fungicides to control these diseases and use of chemical fertilizers to promote plant growth and crop yield have widely affected the agroecosystem and have various detrimental effects and numerous side effects. Sustainable control of such plant diseases has been an important challenge to agricultural field. Continuous search for eco-friendly management of plant disease and promotion of plant growth and crop yield has headed toward the use of plant growth-promoting rhizobacteria (PGPR) as an effective and eco-friendly means of controlling soil-borne phytopathogens and simultaneously promoting the plant growth. This chapter focuses on various aspects and mechanisms of biocontrol of plant pathogens; plant growth promotion, commercialization of their wide applications, and future prospects of PGPR are also discussed.
Citations
More filters
TL;DR: This review emphasizes the development of biofungicides products from screening to marketing and the problems that hinder their development and particular attention was given to the gaps observed in this sector and factors that hamper its development, particularly in terms of efficacy and legislation procedures.
Abstract: The increase in the world population has generated an important need for both quality and quantity agricultural products, which has led to a significant surge in the use of chemical pesticides to fight crop diseases. Consumers, however, have become very concerned in recent years over the side effects of chemical fungicides on human health and the environment. As a result, research into alternative solutions to protect crops has been imposed and attracted wide attention from researchers worldwide. Among these alternatives, biological controls through beneficial microorganisms have gained considerable importance, whilst several biological control agents (BCAs) have been screened, among them Bacillus, Pantoea, Streptomyces, Trichoderma, Clonostachys, Pseudomonas, Burkholderia, and certain yeasts. At present, biopesticide products have been developed and marketed either to fight leaf diseases, root diseases, or fruit storage diseases. However, no positive correlation has been observed between the number of screened BCAs and available marketed products. Therefore, this review emphasizes the development of biofungicides products from screening to marketing and the problems that hinder their development. Finally, particular attention was given to the gaps observed in this sector and factors that hamper its development, particularly in terms of efficacy and legislation procedures.
107 citations
TL;DR: A brief review emphasizing the applicability of BPBs as an innovative exertion to fulfill the current food crisis is presented here is a brief review.
Abstract: This review presents a comprehensive and systematic study of the field of bacterial plant biostimulants and considers the fundamental and innovative principles underlying this technology. Plant biostimulants are an important tool for modern agriculture as part of an integrated crop management (ICM) system, helping make agriculture more sustainable and resilient. Plant biostimulants contain substance(s) and/or microorganisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to enhance plant nutrient uptake, nutrient use efficiency, tolerance to abiotic stress, biocontrol, and crop quality. The use of plant biostimulants has gained substantial and significant heed worldwide as an environmentally friendly alternative to sustainable agricultural production. At present, there is an increasing curiosity in industry and researchers about microbial biostimulants, especially bacterial plant biostimulants (BPBs), to improve crop growth and productivity. The BPBs that are based on PGPR (plant growth-promoting rhizobacteria) play plausible roles to promote/stimulate crop plant growth through several mechanisms that include (i) nutrient acquisition by nitrogen (N2) fixation and solubilization of insoluble minerals (P, K, Zn), organic acids and siderophores; (ii) antimicrobial metabolites and various lytic enzymes; (iii) the action of growth regulators and stress-responsive/induced phytohormones; (iv) ameliorating abiotic stress such as drought, high soil salinity, extreme temperatures, oxidative stress, and heavy metals by using different modes of action; and (v) plant defense induction modes. Presented here is a brief review emphasizing the applicability of BPBs as an innovative exertion to fulfill the current food crisis.
100 citations
01 Jan 2017
TL;DR: This review focuses on the different aspects of various hydrolytic enzymes produced by rhizoflora and their role in sustainable biocontrol of phytopathogens.
Abstract: Microbial community in the rhizosphere produces a variety of hydrolytic enzymes that are responsible for the degradation of various components of fungal pathogens. The extracellular hydrolytic enzymes excreted by soil rhizobia degrade cell wall components of plant pathogenic microbes. The enzymes of these types are able to breakdown glycosidic linkages present in the polysaccharide of the cell wall of phytopathogens. In this regard, plant growth-promoting rhizobacteria (PGPR) are known to colonize rhizosphere and enhance plant growth through different mechanisms that include (i) plant growth promotion and (ii) biological control of plant disease. Plant growth promotion mechanisms include mineralization of insoluble substances, production of plant growth hormones, biological nitrogen fixation, and promotion of root growth. Biocontrol mechanism involves competition, antibiosis, parasitism, induction of systemic acquired resistance (SAR), induction of systemic resistance (ISR), soil suppressiveness, and production of various antifungal metabolites; hydrolytic enzymes such as chitinase, glucanase, protease, and cellulase; and antibiotics such as 2,4-diacetyl phloroglucinol (DAPG), amphisin, oomycin A, hydrogen cyanide, phenazine, pyoluteorin, pyrrolnitrin, cyclic lipopeptides, oligomycin A, zwittermicin A, kanosamine, and xanthobaccin. Production of hydrolytic enzymes by PGPR is an important mechanism directed against phytopathogens for sustainable plant disease management. These enzymes break down the cell wall of fungal pathogens causing cell death. This review focuses on the different aspects of various hydrolytic enzymes produced by rhizoflora and their role in sustainable biocontrol of phytopathogens.
85 citations
02 Mar 2021
TL;DR: A brief review emphasizing the applicability of BPBs as an innovative exertion to fulfill the current food crisis is presented here is a brief review.
Abstract: This review presents a comprehensive and systematic study of the field of bacterial plant biostimulants and considers the fundamental and innovative principles underlying this technology. Plant biostimulants are an important tool for modern agriculture as part of an integrated crop management (ICM) system, helping make agriculture more sustainable and resilient. Plant biostimulants contain substance(s) and/or microorganisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to enhance plant nutrient uptake, nutrient use efficiency, tolerance to abiotic stress, biocontrol, and crop quality. The use of plant biostimulants has gained substantial and significant heed worldwide as an environmentally friendly alternative to sustainable agricultural production. At present, there is an increasing curiosity in industry and researchers about microbial biostimulants, especially bacterial plant biostimulants (BPBs), to improve crop growth and productivity. The BPBs that are based on PGPR (plant growth-promoting rhizobacteria) play plausible roles to promote/stimulate crop plant growth through several mechanisms that include (i) nutrient acquisition by nitrogen (N2) fixation and solubilization of insoluble minerals (P, K, Zn), organic acids and siderophores; (ii) antimicrobial metabolites and various lytic enzymes; (iii) the action of growth regulators and stress-responsive/induced phytohormones; (iv) ameliorating abiotic stress such as drought, high soil salinity, extreme temperatures, oxidative stress, and heavy metals by using different modes of action; and (v) plant defense induction modes. Presented here is a brief review emphasizing the applicability of BPBs as an innovative exertion to fulfill the current food crisis.
69 citations
TL;DR: In this article, the authors reported the isolation of phytase positive multifarious Klebsiella variicola SURYA6 isolated from wheat rhizosphere in Kolhapur, India.
Abstract: Bacteria that surround plant roots and exert beneficial effects on plant growth are known as plant growth-promoting rhizobacteria (PGPR). In addition to the plant growth-promotion, PGPR also imparts resistance against salinity and oxidative stress and needs to be studied. Such PGPR can function as dynamic bioinoculants under salinity conditions. The present study reports the isolation of phytase positive multifarious Klebsiella variicola SURYA6 isolated from wheat rhizosphere in Kolhapur, India. The isolate produced various plant growth-promoting (PGP), salinity ameliorating, and antioxidant traits. It produced organic acid, yielded a higher phosphorous solubilization index (9.3), maximum phytase activity (376.67 ± 2.77 U/mL), and copious amounts of siderophore (79.0%). The isolate also produced salt ameliorating traits such as indole acetic acid (78.45 ± 1.9 µg/mL), 1 aminocyclopropane-1-carboxylate deaminase (0.991 M/mg/h), and exopolysaccharides (32.2 ± 1.2 g/L). In addition to these, the isolate also produced higher activities of antioxidant enzymes like superoxide dismutase (13.86 IU/mg protein), catalase (0.053 IU/mg protein), and glutathione oxidase (22.12 µg/mg protein) at various salt levels. The isolate exhibited optimum growth and maximum secretion of these metabolites during the log-phase growth. It exhibited sensitivity to a wide range of antibiotics and did not produce hemolysis on blood agar, indicative of its non-pathogenic nature. The potential of K. variicola to produce copious amounts of various PGP, salt ameliorating, and antioxidant metabolites make it a potential bioinoculant for salinity stress management.
56 citations
References
More filters
TL;DR: This review restricts itself to bacteria that are derived from and exert this effect on the root and generally designated as PGPR (plant-growth-promoting rhizobacteria), which can be direct or indirect in their effects on plant growth.
Abstract: Several microbes promote plant growth, and many microbial products that stimulate plant growth have been marketed. In this review we restrict ourselves to bacteria that are derived from and exert this effect on the root. Such bacteria are generally designated as PGPR (plant-growth-promoting rhizobacteria). The beneficial effects of these rhizobacteria on plant growth can be direct or indirect. This review begins with describing the conditions under which bacteria live in the rhizosphere. To exert their beneficial effects, bacteria usually must colonize the root surface efficiently. Therefore, bacterial traits required for root colonization are subsequently described. Finally, several mechanisms by which microbes can act beneficially on plant growth are described. Examples of direct plant growth promotion that are discussed include (a) biofertilization, (b) stimulation of root growth, (c) rhizoremediation, and (d) plant stress control. Mechanisms of biological control by which rhizobacteria can promote plant growth indirectly, i.e., by reducing the level of disease, include antibiosis, induction of systemic resistance, and competition for nutrients and niches.
3,761 citations
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.
2,982 citations
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
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
11 Oct 2012
TL;DR: It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies.
Abstract: The worldwide increases in both environmental damage and human population pressure have the unfortunate consequence that global food production may soon become insufficient to feed all of the world's people. It is therefore essential that agricultural productivity be significantly increased within the next few decades. To this end, agricultural practice is moving toward a more sustainable and environmentally friendly approach. This includes both the increasing use of transgenic plants and plant growth-promoting bacteria as a part of mainstream agricultural practice. Here, a number of the mechanisms utilized by plant growth-promoting bacteria are discussed and considered. It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies. While there may not be one simple strategy that can effectively promote the growth of all plants under all conditions, some of the strategies that are discussed already show great promise.
2,094 citations