Plant growth promoting rhizobacteria as biofertilizers
Numerous species of soil bacteria which flourish within the rhizosphere of plants, but which can grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively referred to as PGPR (plant growth promoting rhizobacteria). The look for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to take advantage of them commercially as biofertilizers. After an initial clarification of the term biofertilizers and therefore the nature of associations between PGPR and plants (i.e., endophytic versus rhizospheric), this review focuses on the known, the putative, and therefore the speculative modes-of-action of PGPR. These modes of action include fixing N2, increasing the supply of nutrients within the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses. [1]
Mechanisms and applications of plant growth promoting rhizobacteria: Current perspective
Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the basis surface and are directly or indirectly involved in promoting plant growth and development via production and secretion of varied regulatory chemicals within the vicinity of rhizosphere. Generally, plant growth promoting rhizobacteria facilitate the plant growth directly by either assisting in resource acquisition (nitrogen, phosphorus and essential minerals) or modulating phytohormone levels, or indirectly by decreasing the inhibitory effects of varied pathogens on plant growth and development within the sorts of biocontrol agents. Various studies have documented the increased health and productivity of various plant species by the appliance of plant growth promoting rhizobacteria under both normal and stressed conditions. The plant-beneficial rhizobacteria may decrease the worldwide dependence on hazardous agricultural chemicals which destabilize the agro-ecosystems. [2]
Plant growth promoting rhizobacteria and endophytes accelerate phytoremediation of metalliferous soils
Technogenic activities (industrial—plastic, textiles, microelectronics, wood preservatives; mining—mine refuse, tailings, smelting; agrochemicals—chemical fertilizers, farm yard manure, pesticides; aerosols—pyrometallurgical and automobile exhausts; biosolids—sewage sludge, domestic waste; fly ash—coal combustion products) are the first sources of heavy metal contamination and pollution within the environment additionally to geogenic sources. During the last 20 years, bioremediation has emerged as a possible tool to wash up the metal-contaminated/polluted environment. Exclusively derived processes by plants alone (phytoremediation) are time-consuming. Further, high levels of pollutants pose toxicity to the remediating plants. [3]
Plant growth promoting rhizobacteria Dietzia natronolimnaea modulates the expression of stress responsive genes providing protection of wheat from salinity stress
Plant growth promoting rhizobacteria (PGPR) hold promising future for sustainable agriculture. Here, we demonstrate a carotenoid producing halotolerant PGPR Dietzia natronolimnaea STR1 protecting wheat plants from salt stress by modulating the transcriptional machinery liable for salinity tolerance in plants. The expression studies confirmed the involvement of ABA-signalling cascade, as TaABARE and TaOPR1 were upregulated in PGPR inoculated plants resulting in induction of TaMYB and TaWRKY expression followed by stimulation of expression of a plethora of stress related genes. [4]
Profiling Rhizosphere Microbes on the Root of Maize (Zea mays) Planted in an Alfisol for Selection as Plant Growth Promoting Rhizobacteria (PGPR)
Maize (Zea mays L. Merill) root rhizosphere, being a metabolite-enriched niche was profiled with the target of isolating Plant Growth Promoting Rhizobacteria (PGPR) for bio-fertilizer production. Isolation was administered from the basis surface and rhizosphere soil samples of the plant using standard procedures. Cultural, physiological and biochemical procedures were wont to identify the isolates. Eighty (80) isolates obtained were screened for growth promoting attributes and sixteen (16) representative isolates selected, and further identified using molecular methods by sequencing of their 16S rDNA gene. Sixty three percent of the characterized organisms exhibited sequence homology level equal or greater than 90% with those of the gene bank. [5]
Reference
[1] Vessey, J.K., 2003. Plant growth promoting rhizobacteria as biofertilizers. Plant and soil, 255(2), (Web Link)
[2] Ahemad, M. and Kibret, M., 2014. Mechanisms and applications of plant growth promoting rhizobacteria: current perspective. Journal of King saud University-science, 26(1), (Web Link)
[3] Ma, Y., Prasad, M.N.V., Rajkumar, M. and Freitas, H., 2011. Plant growth promoting rhizobacteria and endophytes accelerate phytoremediation of metalliferous soils. Biotechnology advances, 29(2), (Web Link)
[4] Plant growth promoting rhizobacteria Dietzia natronolimnaea modulates the expression of stress responsive genes providing protection of wheat from salinity stress
Nidhi Bharti, Shiv Shanker Pandey, Deepti Barnawal, Vikas Kumar Patel & Alok Kalra
Scientific Reports volume 6, (Web Link)
[5] Taiwo, L. B., Ailenokhuoria, B. V. and Oyedele, A. O. (2017) “Profiling Rhizosphere Microbes on the Root of Maize (Zea mays) Planted in an Alfisol for Selection as Plant Growth Promoting Rhizobacteria (PGPR)”, Microbiology Research Journal International, 21(5), (Web Link)