Pinakin Dhandhukia

Screening of PGPR from saline desert of Kutch: growth promotion in Arachis hypogea by Bacillus licheniformis A2.

Rhizosphere of a halotolerant plant Suaeda fruticosa from saline desert of Little Rann of Kutch, Gujarat (India) was explored for isolation of PGPR form the rare ecological niche having4.33% salinity. Total 85 isolates from the rhizosphere belonging to different species were isolated. Out of 85 isolates, 23 could solubilize phosphate and 11 isolates produced IAA. Seven isolates showed both the traits of phosphate solubilization and IAA production. All isolates which showed either of IAA production or phosphate solubilization or both were further screened for other PGP traits like production of ammonia, siderophore, chitinase, HCN and assessment of their antifungal activity. Out of all the screened isolates, Bacillus licheniformis strain A2 showed most prominent PGP traits in vitro and it was tested in vivo for growth promotion of Groundnut (Arachis hypogaea) under saline soil condition. In presence of soil supplemented with 50 mM NaCl, B. licheniformis treated plants showed increase in fresh biomass, total length and root length by 28%, 24% and 17% and in absence of NaCl it was 43%, 31% and 39% respectively.

Portraying mechanics of plant growth promoting rhizobacteria (PGPR): A review

Abstract Population growth and increase in food requirement is the global problem. It is inevitable to introduce new practices that help to increase agricultural productivity. Use of plant growth promoting rhizobacteria (PGPR) has shown potentials to be a promising technique in the practice of sustainable agriculture. A group of natural soil microbial flora acquire dwelling in the rhizosphere and on the surface of the plant roots which impose beneficial effect on the overall well-being of the plant are categorized as PGPR. Researchers are actively involved in understanding plant growth promoting mechanics employed by PGPR. Broadly, these are divided into direct and indirect mechanics. Any mechanism that directly enhances plant growth either by providing nutrients or by producing growth regulators are portrayed as direct mechanics. Whereas, any mechanisms that protects plant from acquiring infections (biotic stress) or helps plant to grow healthily under environmental stresses (abiotic stress) are considered indirect mechanics. This review is focused to describe cogent mechanics employed by PGPR that assists plant to sustain healthy growth. Also, we emphasized on the PGPR-based products which have been commercially developed exploiting these mechanics of PGPR.

Plant growth promoting potentials of Pseudomonas spp. strain OG isolated from marine water

Abstract Bacterium Pseudomonas spp. olive green (OG) was isolated from marine water, yet, it was characterized as plant growth promoting bacterium (PGPB). Multiple plant growth promoting traits of OG isolate were determined in vitro. It was tested positive for Indole-3-acetic acid (IAA) production with 29 µg ml−1 of IAA yield, phosphate solubilization with 34 µg ml−1 solubilization of Tri-calcium-phosphate and it showed maximum of 32 µg ml−1 of ammonia production. OG isolate was affirming siderophore production, hydrocyanic acid (HCN) production and catalase production. 16S rRNA gene sequence comparison was used to identify the isolate which showed its closest neighbor to be Pseudomonas fluoroscens strain BCPBMS-1. Efficacy of this PGPB was tested on the seedling growth of two test plants chickpea and green gram. Both the test plants treated with OG-based talc bioformulation showed significant growth promotion. Chickpea showed enhanced overall fresh biomass by 24%, overall dry biomass by 27% was observed after 15 days of seeded in pots. Green gram showed enhanced overall dry biomass by 28% was observed after 10 days of seeded in pots.

Delineating Kocuria turfanensis 2M4 as a credible PGPR: a novel IAA-producing bacteria isolated from saline desert

Indole-3-acetic acid (IAA)-producing bacteria Kocuria turfanensis strain 2M4 was isolated from the rhizospheric soil of halotolerant plant Suaeda fruticosa from a unique saline desert of Little Rann of Kutch, Gujarat, India. Rhizobacteria was bright orange pigmented, gram-positive, coccoid, non-endospore forming, and aerobic in nature. 16S rRNA gene sequence analysis showed that 2M4 isolate matched best with type strain of K. turfanensis HO-9042T. Isolate optimally produced 38 µg ml−1 IAA when growth medium was supplemented with 600 µg ml−1 of L-tryptophan. Thin layer chromatography and Fourier transform infrared spectroscopy analysis were performed to corroborate IAA production. To characterize rhizobacterial isolate as a plant growth-promoting bacteria, it was tested for phosphate solubilization where it solubilized maximum 12 µg ml−1 phosphate in presence of fructose, produced 53% siderophore units under iron-free minimal MM9 medium and produced 1.8 µmol ml−1 ammonia in peptone water broth. Plant growth promotion by test isolate was studied on groundnut (Arachis hypogaea L.) under non-saline and saline soil. There was increase by 18% in total plant length and 30% in fresh biomass observed under non-saline control soil. Under saline soil, test isolate showed 17% increase in total length of the plant and 13% increase in fresh biomass.

Simultaneous detection and quantification of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) produced by rhizobacteria from l-tryptophan (Trp) using HPTLC

A simple, quick and reliable method is proposed for the detection and quantitation of indole-3-acetate (IAA) and indole-3-butyrate (IBA), an auxin phytohormone produced by rhizobacteria from l-tryptophan (Trp) metabolism using high performance thin-layer chromatography (HPTLC). Microbial auxin biosynthesis routes involve Trp as a precursor where other than IAA and IBA, products such as indole-3-pyruvate (IPA), indole-3-acetamide (IAM), tryptamine, indole-3-acetonitrile (IAN), indole-3-lactic acid (ILA) and indole-3-acetaldehyde (IAAld) are also produced. In traditional spectrophotometric method, Salkowski reagent develops color by reacting with indolic compounds. The color development is non-specific contributed by several Trp derivatives produced by rhizobacteria rather than IAA only. To overcome this limitation, HPTLC based protocol is developed to precisely detect and quantify IAA and IBA in the range of 100 to 1000ng per spot. This protocol is applicable to detect and quantify IAA and IBA from microbial samples ignoring other Trp derivatives. For microbial samples, the spectrophotometric method gives larger values as compared to HPTLC derived values which may be attributed by total indolic compounds reacting with Salkowski reagent rather than only IAA and/or IBA.

Biosynthesis of Gold Nanoparticles Using Fusarium oxysporum f. sp. cubense JT1, a Plant Pathogenic Fungus

The development of reliable processes for the synthesis of gold nanoparticles is an important aspect of current nanotechnology research. Recently, reports are published on the extracellular as well as intracellular biosynthesis of gold nanoparticles using microorganisms. However, these methods of synthesis are rather slow. In present study, rapid and extracellular synthesis of gold nanoparticles using a plant pathogenic fungus F. oxysporum f. sp. cubense JT1 (FocJT1) is reported. Incubation of FocJT1 mycelium with auric chloride solution produces gold nanoparticles in 60 min. Gold nanoparticles were characterized by UV-Vis spectroscopy, FTIR, and particle size analysis. The particles synthesized were of 22 nm sized, capped by proteins, and posed antimicrobial activity against Pseudomonas sp.

Induction of Defense-Related Enzymes in Banana Plants: Effect of Live and Dead Pathogenic Strain of Fusarium oxysporum f. sp. cubense

The aim of the present study was to scrutinize the response of banana (Grand Naine variety) plants when interacting with dead or live pathogen, Fusarium oxysporum f.sp. cubense, a causative agent of Panama disease. Response of plants was evaluated in terms of induction of defense-related marker enzyme activity, namely, peroxidase (POX), polyphenol oxidase (PPO), β-1,3 glucanase, chitinase, and phenolics. Plants interaction with live pathogen resulted in early induction of defense to restrain penetration as well as antimicrobial productions. However, pathogen overcame the defense of plant and caused disease. Interaction with dead pathogen resulted in escalating defense response in plants. Later on plants inoculated with dead pathogen showed resistance to even forced inoculation of live pathogen. Results obtained in the present study suggest that dead pathogen was able to mount defense response in plants and provide resistance to Panama disease upon subsequent exposure. Therefore, preparation from dead pathogen could be a potential candidate as a biocontrol agent or plant vaccine to combat Panama disease.

Describing Paenibacillus mucilaginosus strain N3 as an efficient plant growth promoting rhizobacteria (PGPR)

Abstract Bacterium Paenibacillus mucilaginosus strain N3 was isolated from agricultural farm soil (located at Boriavi village, Gujarat, India). Isolate showed an evidence of non-symbiotic nitrogen fixation, when grown in nitrogen-free bromothymol blue growth medium. It was tested positive for direct plant-growth-promoting traits like Indole-3-acetic acid production, solubilization of Tri-calcium-phosphate, and ammonia production. Further, N3 isolate was tested positive for siderophore production of catecholate type and catalase production as an indirect plant-growth-promoting trait. Biochemical tests along with 16s rRNA gene sequence analysis confirmed the strain N3 to be P. mucilaginosus. To determine its efficacy as a plant-growth-promoting rhizobacteria (PGPR), its talc-based biofertilizer was prepared and tested on the growth of green gram (Vigna radiata). Seeds treated with this biofertilizer showed an increase in overall dry biomass by 17% and sapling length by 28% (as compared to non-treated controls) after 10 days of sowing in pots. Thus, multiple plant-growth-promoting traits of P. mucilaginosus N3 determined in vitro along with its ability to promote growth in green gram in vivo we characterize this strain as an efficient PGPR.

Induction of defence-related enzymes in susceptible variety of banana: role of Fusarium-derived elicitors

Elicitor prepared from the Fusarium oxysporum f. sp cubense (Foc) isolated from infected banana rhizosphere induced the accumulation of resistance-associated enzymes in leaves of susceptible and resistant variety of banana. Roots of Grand Naine (susceptible) and robusta (resistant) variety were inoculated with 1 g/l Foc elicitors. Distinct difference in peroxidase, polyphenol oxidase, β-1,3-glucanase, chitinase and phenolics was observed in control plants of resistant and susceptible varieties. Induced defence-related enzymes in susceptible variety were increased tothe level of untreated resistant variety. This depicted that Fusarium-derived elicitor effectively induced defence in susceptible variety to the apparent level of untreated resistant variety.

Techniques to Study Microbial Phytohormones

Soil is replete with microscopic life such as bacteria, fungi, actinomycetes, protozoa and algae. Microscopic life tends to reside in the rhizosphere of the soil and interact with plants. A microbial–plant interaction occurs due to the microbial ability to produce phytohormones regarded as the “classical five,” which are auxin, gibberellin, cytokinins, ethylene and abscisic acid. In addition to these modulators, jasmonic and salicylic acid are also documented as bacterial hormones contributing to a sustainable agro system. Auxins, gibberellins and cytokinins are known to be produced by Azospirillum species. Auxin production in fungus such as Pistolithus tinctorius leads to promotion of plant growth and different bacterial species show effect on root length by increasing the surface area and induction of gall and tumor formations. Gibberellins are tetracyclic diterpenoid acids that are involved in a number of developmental, reproduction and floral formation in plants, while plant growth promotion and induction of tumor and gall formation are done by cytokinins. Pseudomonas solanacearum, Mycobacterium hiemalis and largely spore forming bacteria have shown to form ethylene in culture. Abscisic acid (ABA) is a stress-related signaling molecule reported in all kingdoms of life such as plant-associated bacteria, plant pathogenic fungi, certain cyanobacteria, algae, lichens, protozoa and sponges. Salicylic acid is synthesized by the fungus P. patulum and it is an effective therapeutic agent for plants. SA plays a role in plant response during biotic and abiotic stress. It also regulates physiological and biochemical processes during the plant lifespan. Jasmonic acid is a signaling molecule involved in plant defense reported to be produced by fungus Lasiodiplodia theobromae. However, despite the significant research pursued in this area, there are limited reports suggesting strategies that focus on the production, extraction and detection of microbial phytohormones. Here, the present review focuses on the techniques used for isolation and purification of these phytohormones.