Soil salinity: A serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation.

Mechanisms and applications of plant growth promoting rhizobacteria: Current perspective

B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

Using soil bacteria to facilitate phytoremediation.

Microbes of the phytomicrobiome are associated with every plant tissue and, in combination with the plant form the holobiont. Plants regulate the composition and activity of their associated bacterial community carefully. These microbes provide a wide range of services and benefits to the plant; in return, the plant provides the microbial community with reduced carbon and other metabolites. Soils are generally a moist environment, rich in reduced carbon which supports extensive soil microbial communities. The rhizomicrobiome is of great importance to agriculture owing to the rich diversity of root exudates and plant cell debris that attract diverse and unique patterns of microbial colonization. Microbes of the rhizomicrobiome play key roles in nutrient acquisition and assimilation, improved soil texture, secreting, and modulating extracellular molecules such as hormones, secondary metabolites, antibiotics, and various signal compounds, all leading to enhancement of plant growth. The microbes and compounds they secrete constitute valuable biostimulants and play pivotal roles in modulating plant stress responses. Research has demonstrated that inoculating plants with plant-growth promoting rhizobacteria (PGPR) or treating plants with microbe-to-plant signal compounds can be an effective strategy to stimulate crop growth. Furthermore, these strategies can improve crop tolerance for the abiotic stresses (e.g., drought, heat, and salinity) likely to become more frequent as climate change conditions continue to develop. This discovery has resulted in multifunctional PGPR-based formulations for commercial agriculture, to minimize the use of synthetic fertilizers and agrochemicals. This review is an update about the role of PGPR in agriculture, from their collection to commercialization as low-cost commercial agricultural inputs. First, we introduce the concept and role of the phytomicrobiome and the agricultural context underlying food security in the 21st century. Next, mechanisms of plant growth promotion by PGPR are discussed, including signal exchange between plant roots and PGPR and how these relationships modulate plant abiotic stress responses via induced systemic resistance. On the application side, strategies are discussed to improve rhizosphere colonization by PGPR inoculants. The final sections of the paper describe the applications of PGPR in 21st century agriculture and the roadmap to commercialization of a PGPR-based technology.

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Plant Growth-Promoting Rhizobacteria: Context, Mechanisms of Action, and Roadmap to Commercialization of Biostimulants for Sustainable Agriculture.

Salinity is one of the major anthropogenic as well as environmental stresses that reduce plant growth. Results show that even after being adapted up to 6% sodium chloride (NaCl) concentration, all selected isolates were able to solubilize phosphate, and produce phytohormones, siderophores and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme. NT1 was found to exhibit the highest phosphate solubilization zones (25 mm), siderophore production (1000 µg ml−1) as well as ACC deaminase production (50 µMmg−1h−1) potential under laboratory conditions. On the other hand, pot studies conducted on tomato plants under 2% NaCl stress proved that C4 and T15 were the best growth promoters. C4 showed 50% enhancement in root and shoot length as compared to NaCl added untreated plants as well as in absence of NaCl. C4 also enhanced salinity tolerance in plants with the lowest uptake of NaCl thereby reducing the salt stress on plants. C5 enhanced biomass production in tomato plants with increased uptake ...

https://www.tandfonline.com/doi/pdf/10.1080/17429140903125848

Salinity-resistant plant growth promoting rhizobacteria ameliorates sodium chloride stress on tomato plants

Role of allelochemicals in plant growth promoting rhizobacteria for biocontrol of phytopathogens

Soil microbial communities are often difficult to characterize, mainly because of their immense phenotypic and genotypic diversity. In the last ten years, a number of PGPR that have been identified has seen a great boost, mainly because the role of the rhizosphere as an ecological unit has gained importance in the functioning of the biosphere and also because mechanisms of action of PGPR have been deeply studied. A putative PGPR qualifies as PGPR when it is able to produce a positive effect on the plant upon inoculation, hence demonstrating good competitive skills over the existing rhizosphere communities. PGPR influence direct growth promotion of plants by fixing atmospheric nitrogen, Solubilizing insoluble phosphates, secreting hormones such as IAA, GAs, and Kinetins besides ACC (1-Aminocycloprapane-1-carboxylic acid) deaminase production, which helps in regulation of ethylene. Induced systemic resistance (ISR), antibiosis, competition for nutrients, parasitism, production of metabolites (hydrogen cyanide, siderophores) suppressive to deleterious rhizobacteria are some of the mechanism that indirectly benefit plant growth.

Plant growth promoting Rhizobacteria (PGPR): a review

Phytoremediation i.e. the use of plants to adsorb, accumulate or detoxify contaminants is an emerging area of interest. A viable technology needs optimum biomass production in metal contaminated soil. Five strains of microbes were selected after testing their potential as plant growth promoters, on the basis of their phosphate solubilization ability, IAA, siderophore and HCN production and biocontrol potentials. They were examined for growth in synthetic medium supplemented with nickel and their MIC (2 mM) was determined. These isolates were also able to grow and produce siderophores in presence of heavy metals like Ni, Zn and Cd. A positive response of bacterial inoculants was observed in chickpea plants towards toxic effect of nickel present in soil at different concentration (0, 1 and 2 mM). Bacterial inoculants enhanced fresh and dry weight of plants even at 2 mM nickel concentration. Pot experiments indicated that presence of nickel at upto 1 mM enhanced plant growth compared to uninoculated nickel free plants. The accumulation of nickel/plant was just 50% in Pseudomonas inoculated plants as compared to uninoculated plants with 2 mM nickel concentration along with increased biomass. The results suggest the use of these PGPR to enhance plant growth in nickel-spiked land and remediate nickel from contaminated sites. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Enhancement of plant growth and decontamination of nickel-spiked soil using PGPR.

The health of the plant and soil fertility is dependent on the plant–microbes interaction in the rhizosphere. Microbial life tends to endure various rhizosphere plant–microbe interactions. Phytohor...

https://tandfonline.com/doi/pdf/10.1080/17429145.2017.1392625

Meenu Saraf

Papers

Salinity-resistant plant growth promoting rhizobacteria ameliorates sodium chloride stress on tomato plants

Role of allelochemicals in plant growth promoting rhizobacteria for biocontrol of phytopathogens

Plant growth promoting Rhizobacteria (PGPR): a review

Enhancement of plant growth and decontamination of nickel-spiked soil using PGPR.

Biosynthesis of phytohormones from novel rhizobacterial isolates and their in vitro plant growth-promoting efficacy.