Production Of Plant Growth Regulators Research Articles

Correlation between physico-chemical attributes of Rhizospheric soils from agricultural fields of semi-arid Kachchh, Gujarat, Western India

Agriculture worldwide relies significantly on the quality of soil and water. This becomes particularly challenging in arid regions, given that salinity or sodicity poses additional issues. PGPR are common inhabitants that colonize plant roots and enhance yield by producing plant growth regulators. With this background, the present study was designed to assess the physico-chemical and microbiological attributes of soils from agricultural fields of different taluka of Kachchh, Gujarat, India. A total of 34 soil samples were collected during pre and post-monsoon seasons and characterized for various physico-chemical properties including nutrients. The study revealed that the mean values of N, P, and K during pre and post-monsoon season were 4.95%, 47.16 mg/kg, 119.62 mg/kg and 5.20%, 53.67 mg/kg, and 180.45 mg/kg respectively. The maximum chloride concentration in the soil was 2917.40 mg/kg during the pre-monsoon season was reflected in the salinity status (5.27 ppt). Pearson’s correlation coefficient was calculated to understand the relationship between the physico-chemical properties.

Optimization and reactor-scale production of plant growth regulators by Pleurotus eryngii.

The aims of the this study are to select the best cultivation type for plant growth regulator (PGR) production, to optimize PGR production with statistical experimental design, and to calculate bioprocess parameters and yield factors during PGR production by P. eryngii in flask and reactor scales. Submerged fermentation was the best cultivation type with 4438.67 ± 37.14, 436.95 ± 27.31, and 54.32 ± 3.21mg/L of GA3, ABA, and IAA production values, respectively. The Plackett-Burman and Box-Behnken designs were used to determine effective culture parameters and interactive effects of the selected culture parameters on PGR production by Pleurotus eryngii under submerged fermentation. The statistical model is valid for predicting PGR production by P. eryngii. After these studies, maximum PGR production (7926.17 ± 334.09, 634.92 ± 12.15, and 55.41 ± 4.38mg/L for GA3, ABA, and IAA, respectively) was reached on the 18th day of fermentation under optimized conditions. The optimum formula was 50g/L fructose, 3g/L NaNO3, and 1.5g/L KH2PO4, 1mg/L thiamine, incubation temperature 25°C, initial medium pH 7.0, and an agitation speed of 150rpm. The kinetics of PGR production was investigated in batch cultivation under 3-L stirred tank reactor conditions. Concentrations of GA3, ABA, and IAA of 10,545.00 ± 527.25, 872.32 ± 21.81, and 60.48 ± 3.48mg/L were obtained at the reactor scale which were 4.1, 3.4, and 2.3 times higher than the initial screening values. The specific growth rate (µ), the volumetric (rp) and specific (Qp) PGR production rates, 486.11mg/L/day and 107.43mg/g biomass/day for GA3, confirmed the successful transfer of optimized conditions to the reactor scale. In the presented study, PGR production of P. eryngii is reported for the first time.

Flask and reactor scale production of plant growth regulators by Inonotus hispidus: optimization, immobilization and kinetic parameters

The aims of the presented study are to compare submerged, static, and solid-state fermentation in the production of gibberellic acid (GA3), indole acetic acid (IAA), and abscisic acid (ABA) by Inonotus hispidus, to optimize with a statistical approach, and to determine the kinetic parameters under flask and reactor conditions. The maximum concentrations of GA3, (2478.85 ± 68.53 mg/L), ABA, (273.26 ± 6.17 mg/L) and IAA (30.67 ± 0.19 mg/L) were obtained in submerged conditions. After optimization, these values reached 2998.85 ± 28.85, 339.47 ± 5.50, and 34.56 ± 0.25 mg/L, respectively. Immobilization of fungal cells on synthetic fiber, polyurethane foam, and alginate beads resulted in an increase in plant growth regulators (PGR) production by 5.53%− 5.79% under optimized conditions. At the reactor scale, a significant increase was observed for GA3 concentration, 5441.54 mg/L, which was 2.14 and 1.45 times higher than non-optimized and optimized conditions in the flask scale, respectively. The maximum values for ABA and IAA were 390.39 and 44.79 mg/L, respectively. Although the specific growth rate (µ) decreases relatively from non-optimized flask conditions to optimized reactor conditions, it was observed that the PGR amounts produced per liter medium (rp) and per gram biomass (Qp) increased significantly. This is the first report on the synthesis of PGR by Inonotus hispidus which could be crucial for sustainable agriculture.

Biodiversity and Functional Attributes of Rhizospheric Microbiomes: Potential Tools for Sustainable Agriculture

The quest for increasing agricultural yield due to increasing population pressure and demands for healthy food has inevitably led to the indiscriminate use of chemical fertilizers. On the contrary, the exposure of the crops to abiotic stress and biotic stress interferes with crop growth further hindering the productivity. Sustainable agricultural practices are of major importance to enhance production and feed the rising population. The use of plant growth promoting (PGP) rhizospheric microbes is emerging as an efficient approach to ameliorate global dependence on chemicals, improve stress tolerance of plants, boost up growth and ensure food security. Rhizosphere associated microbiomes promote the growth by enhancing the uptake of the nutrients, producing plant growth regulators, iron chelating complexes, shaping the root system under stress conditions and decreasing the levels of inhibitory ethylene concentrations and protecting plants from oxidative stress. Plant growth-promoting rhizospheric microbes belong to diverse range of genera including Acinetobacter, Achromobacter, Aspergillus, Bacillus, Burkholderia, Flavobacterium, Klebsiella, Micrococcus, Penicillium, Pseudomonas, Serratia and Trichoderma. Plant growth promoting microbes are an interesting aspect of research for scientific community and a number of formulations of beneficial microbes are also commercially available. Thus, recent progress in our understanding on rhizospheric microbiomes along with their major roles and mechanisms of action under natural and stressful conditions should facilitate their application as a reliable component in the management of sustainable agricultural system. This review highlights the diversity of plant growth promoting rhizospheric microbes, their mechanisms of plant growth promotion, their role under biotic and abiotic stress and status of biofertilizers. The article further focuses on the role of omics approaches in plant growth promoting rhizospheric microbes and draft genome of PGP microbes.

Using plant growth-promoting microorganisms (PGPMs) to improve plant development under in vitro culture conditions.

The use of beneficial microorganisms improves the performance of in vitro - cultured plants through the improvement of plant nutrition, the biological control of microbial pathogens or the production of phytohormones that promote plant growth and development. Plant in vitro culture techniques are highly useful to obtain significant amounts of true-to-type and disease-free plant materials. One of these techniques is clonal micropropagation which consists on the establishment of shoot tip cultures, shoot multiplication, in vitro rooting and acclimatization to ex vitro conditions. However, in some cases, the existence of recalcitrant genotypes, with a compromised multiplication and rooting ability, or the difficulties to overcome the overgrowth of endophytic contaminations might seriously limit its efficiency. In this sense, the establishment of beneficial interactions between plants and plant growth-promoting microorganisms (PGPMs) under in vitro culture conditions might represent a valuable approach to efficiently solve those restrictions. During the last years, significant evidence reporting the use of beneficial microorganisms to improve the yield of in vitro multiplication or rooting as well as their acclimatization to greenhouse or soil conditions have been provided. Most of these positive effects are strongly linked to the ability of these microorganisms to provide in vitro plants with nutrients such as nitrogen or phosphorous, to produce plant growth regulators, to control the growth of pathogens or to mitigate stress conditions. The culture of A. thaliana under aseptic conditions has provided high-quality knowledge on the root development signaling pathways, involving hormones, triggered in the presence of PGPMs. Overall, the present article offers a brief overview of the use of microorganisms to improve in vitro plant performance during the in vitro micropropagation stages, as well as the main mechanisms of plant growth promotion associated with these microorganisms.

Plant Growth Promoting Activity and Biocontrol Potential of Soil Yeast

Among soil microorganisms, yeasts have received little attention as bioonoculant and biocontrol agents in comparison to bacterial, actinomycetes, and filamentous fungal antagonists. The ability of certain taxa of yeasts to multiply rapidly, to produce antibiotics and cell wall-degrading enzymes, to induce resistance of host tissues, and to produce plant growth regulators indicates the potential to exploit them as biocontrol agents and plant growth promoters. We investigated the ability of the soil yeast Rhodotorula sp. and Candida tropicalis to stimulate plant growth promoting characters and biocontrol potential. In vitro culture experiments found that Rhodotorula sp. SY3 (623.14 ug/ml with tryptophan: 150.12 ug/ml without tryptophan) and Candida tropicalis SY5 (580.25 ug/ml - with tryptophan: 120.24 ug/ml - without tryptophan) produces large quantities of indole acetic acid (IAA), but grows rapidly on aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, indicative of high ACC deaminase activity.

Himalayan Microbiomes for Agro-environmental Sustainability: Current Perspectives and Future Challenges.

The Himalayas are one of the most mystical, yet least studied terrains of the world. One of Earth's greatest multifaceted and diverse montane ecosystems is also one of the thirty-four global biodiversity hotspots of the world. These are supposed to have been uplifted about 60-70 million years ago and support, distinct environments, physiography, a variety of orogeny, and great biological diversity (plants, animals, and microbes). Microbes are the pioneer colonizer of the Himalayas that are involved in various bio-geological cycles and play various significant roles. The applications of Himalayan microbiomes inhabiting in lesser to greater Himalayas have been recognized. The researchers explored the applications of indigenous microbiomes in both agricultural and environmental sectors. In agriculture, microbiomes from Himalayan regions have been suggested as better biofertilizers and biopesticides for the crops growing at low temperature and mountainous areas as they help in the alleviation of cold stress and other biotic stresses. Along with alleviation of low temperature, Himalayan microbes also have the capability to enhance plant growth by availing the soluble form of nutrients like nitrogen, phosphorus, potassium, zinc, and iron. These microbes have been recognized for producing plant growth regulators (abscisic acid, auxin, cytokinin, ethylene, and gibberellins). These microbes have been reported for bioremediating the diversepollutants (pesticides, heavy metals, and xenobiotics)for environmental sustainability. In the currentperspectives, presentreview provides a detailed discussion on the ecology, biodiversity, and adaptive features of the native Himalayan microbiomes in view to achieve agro-environmental sustainability.

A Consortium of Rhizosphere-Competent Actinobacteria Exhibiting Multiple Plant Growth-Promoting Traits Improves the Growth of Avicennia marina in the United Arab Emirates

Gray mangrove (Avicennia marina) is the dominant vegetation distributed along the coast of the United Arab Emirates (UAE). Despite its performance as natural coastal guardians, very little is known about the reforestation projects to increase mangrove cover over the years in the UAE and in the Arabian Gulf. Plant growth-promoting actinobacteria (PGPA) were isolated from the mangrove rhizosphere sediments found in the UAE and were evaluated for their potential to produce plant growth regulators (PGRs) and to enhance mangrove growth under seawater irrigation conditions.In vitroscreening identified nine rhizosphere-competent actinobacterial isolates, in a naturally competitive environment, of whichStreptomyces coelicoflavus(Sc) showed a high phosphorus solubilizing activity. Moreover,Streptomyces polychromogenes(Sp),Streptomyces bacillaris(Sb), andStreptomyces ferrugineus(Sf) produced auxins, polyamines (PAs), and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, respectively. Although sediment inoculation with single isolates significantly improved the dry biomass of mangrove shoots (43.2–74.0%) and roots (40.8–75.9%), the consortium of isolates (Sc/Sp/Sb/Sf) caused a greater increase in the dry weight of shoots (82.1%) and roots (81.6%) compared with seawater-irrigated plants (control). In our greenhouse experiments, the levels of photosynthetic pigments,in plantaauxins, and PAs significantly increased in plant tissues inoculated withSc/Sp/Sb/Sf; whereas ACC contents were reduced. This was also evident as the maximum velocity of rubisco carboxylation (Vcmax) increased four-fold in plants treated with the mixture of isolates over control. To the best of our knowledge, this is the first study reporting culturable halotolerant, rhizosphere-competent PGPA inhabiting salty and arid ecosystems applied individually or in combination to promote mangrove growth under harsh conditions such as those found in the Arabian coastal areas.

The role of root‐associated microbes in growth stimulation of plants under saline conditions

AbstractSoil salinization has adverse effects on plant growth due to direct ion toxicity or secondary damage, such as mineral nutrition imbalance and the water stress caused by low osmotic potential. The rhizosphere processes of plants are likely to play an important role in the biological improvement of saline soil. However, the understanding of this remains limited. This review summarizes the progress made recently in exploring the effects of root‐associated microbes especially from halophytic species on the growth stimulation of plants under salinity. For example, halophytes attract and absorb beneficial rhizosphere growth‐promoting bacteria by producing rhizosphere exudates such as organic acids and enzymes, which is conducive to plant growth under salt stress. The plant growth‐promoting exogenous rhizobacteria (PGPR), attached to the roots of halophytes, can promote the growth of plants mainly through the improved absorption of nutrients by the host plants or through producing plant growth regulators. In addition, the colonization of endophytes can regulate plant ion balance and produce secondary metabolites such as growth‐promoting hormone and extracellular enzymes, activating antioxidant systems, and inducing plant system resistance against pathogenic microorganisms, thus promoting the growth of plants under salt stress. The inoculation of arbuscular mycorrhizal fungi (AMF) under salt stress can facilitate plants to change the ion balance or obtain water from the soil, and that the formation of other hyphae may promote the transfer of water and nutrients to plants. Therefore, understanding the effects of root‐associated microbes on the growth stimulation of plants under salinity is of great significance to improving their salt tolerance, so as to improve saline‐alkali land for the construction of a more effective biological improvement model.

The Role of Plant Growth-Promoting Bacteria in Alleviating the Adverse Effects of Drought on Plants

Simple SummaryAmong abiotic stress factors, drought is one of the most detrimental factors in arid and semiarid regions, causing a significant decrease in plant growth and yield in most species, including crops. Under drought conditions, morphological, physiological and biochemical characteristics such as plant height and enzymatic activities are negatively affected. This negative effect may be alleviated with the aid of plant growth-promoting bacteria. Application of plant growth-promoting bacteria such as Paenibacillus, Azospirillum, Rhizobium, Bacillus, Azotobacter, Klebsiella, Pseudomonas and Serratia can enhance hormonal balance, maintain nutrient status and improve plant growth characters as well as increase yield. This review discusses the pivotal role of plant growth-promoting bacteria in mitigating drought stress by improving plant growth characters and yield.Plant growth-promoting bacteria play an essential role in enhancing the physical, chemical and biological characters of soils by facilitating nutrient uptake and water flow, especially under abiotic stress conditions, which are major constrains to agricultural development and production. Drought is one of the most harmful abiotic stress and perhaps the most severe problem facing agricultural sustainability, leading to a severe shortage in crop productivity. Drought affects plant growth by causing hormonal and membrane stability perturbations, nutrient imbalance and physiological disorders. Furthermore, drought causes a remarkable decrease in leaf numbers, relative water content, sugar yield, root yield, chlorophyll a and b and ascorbic acid concentrations. However, the concentrations of total phenolic compounds, electrolyte leakage, lipid peroxidation, amounts of proline, and reactive oxygen species are considerably increased because of drought stress. This negative impact of drought can be eliminated by using plant growth-promoting bacteria (PGPB). Under drought conditions, application of PGPB can improve plant growth by adjusting hormonal balance, maintaining nutrient status and producing plant growth regulators. This role of PGPB positively affects physiological and biochemical characteristics, resulting in increased leaf numbers, sugar yield, relative water content, amounts of photosynthetic pigments and ascorbic acid. Conversely, lipid peroxidation, electrolyte leakage and amounts of proline, total phenolic compounds and reactive oxygen species are decreased under drought in the presence of PGPB. The current review gives an overview on the impact of drought on plants and the pivotal role of PGPB in mitigating the negative effects of drought by enhancing antioxidant defense systems and increasing plant growth and yield to improve sustainable agriculture.

The impact of the rhizobia-legume symbiosis on host root system architecture.

Legumes form symbioses with rhizobia to fix N2 in root nodules to supplement their nitrogen (N) requirements. Many studies have shown how symbioses affect the shoot, but far less is understood about how they modify root development and root system architecture (RSA). RSA is the distribution of roots in space and over time. RSA reflects host resource allocation into below-ground organs and patterns of host resource foraging underpinning its resource acquisition capacity. Recent studies have revealed a more comprehensive relationship between hosts and symbionts: the latter can affect host resource acquisition for phosphate and iron, and the symbiont's production of plant growth regulators can enhance host resource flux and abundance. We review the current understanding of the effects of rhizobia-legume symbioses on legume root systems. We focus on resource acquisition and allocation within the host to conceptualize the effect of symbioses on RSA, and highlight opportunities for new directions of research.

Content and Properties of the By-Products of the Oxidative Degradation of Peat and Their Possible Use

The physical and chemical properties and chemical content of solid residues emerging during the production of plant growth regulators “Oxihumate” and “Peat Oxidate” are studied. The possibility of their use as additions to mineral and organic and mineral fertilizers, soil ameliorants and substrates for vermiculture growing and also as reinforcing additions to the different types of molded fuel is substantiated.

Influence of Plant Growth-Promoting Rhizobacteria on Corn Growth under Drought Stress

ABSTRACTWater availability is a major constraint affecting the growth and yield of crops/plants worldwide. Some studies have shown that specific strains of free-living bacteria found in the plant rhizosphere can improve the tolerance of plants during water stress. A greenhouse study was conducted to evaluate the effects of two mixtures of plant growth-promoting rhizobacteria (PGPR) and two fertilizer sources on root establishment and biomass production of corn (Zea mays L.) during the early growth stages under drought conditions. This study was conducted as a randomized complete block design with five replications. Treatments included three irrigation levels (watering every 3, 6, and 12 days), two fertilizer materials (poultry litter and urea), and two PGPR strain mixtures and a non-inoculated control. Irrigation significantly affected plant growth and biomass accumulation of corn at the V6 to VT stages. Compared to poultry litter, urea application significantly increased plant height, leaf chlorophyll (SPAD readings), leaf area, and plant biomass. PGPR significantly improved plant height, stem diameter, leaf chlorophyll, and root morphology under drought stress conditions. The results demonstrate that PGPR inoculation can stimulate enhanced plant root development (through the production of plant growth regulators), thereby resulting in better absorption of water and nutrients from the soil.

IMPROVING THE TECHNOLOGY OF GROWING PERSACE AND RIPA WITH APPLICATION OF BIOORGANIC BENEFITS

The city ofKamianskebelongs to one of the industrial regions ofUkraine. The whole soil is contaminated with metal compounds, cement dust and chemicals. Therefore, it is necessary to use the bacterial drug «Albobacterin» for the agricultural needs ofUkrainefor the enrichment of soils with nutrients, especially phosphorus compounds.«Albobacterin» – biopreparation is used for the bacteritisation of spring and winter rape seeds in order to improve phosphorus nutrition of plants, protection against phytopathogenic fungi and increase productivity.The nature of the biological action of the drug. The mechanism of action of the drug is related to the property of the bacteria Achromobacteralbum1122 to produce organic acids and enzyme phosphatase, which provides the dissolution of hard-soluble mineral and organic phosphates of the soil, resulting in plants in the process of their development receive additional nutrition with phosphorus from the soil reserves, as well as produce plant growth regulators and vitamins Group B. A.album.1122 bacteria are resistant to a number of pesticides that are used in rape growing technologies.Thus, for the cultivation of «Alborbacterin» rape, the fertilizer is 7% more efficient. For cultivation of pepper «Albobacterin» more efficient mineral fertilizers by 46%. According to the results of qualitative soil indicators in Kamianske, low efficiency of their self-healing is determined, which directly influences the yield of agricultural crops. Based on experimental data, it is necessary to use an additional source of biogenic elements contained in the recommended types of fertilizers.

Production of Plant Growth Regulators by Some Fungi Isolated under Salt Stress

Fifty-eight fungal isolates were isolated from salt soil, whey and salt fish on medium supplemented with 0.5% NaCl. Out of 58 isolates, 49 were capable to grow on medium supplemented with 1 % NaCl. These halo-tolerant isolates were tested to produce plant growth regulators (PGR) on solid or in broth medium. On solid medium, 9 halo-tolerant isolates out of 58 isolates were gave indole acetic acid (IAA) which appeared red zone around growth zone with index ranged from 0.25 to 0.56. While in broth medium, 9 isolates were tried to produce IAA and gibberellic acid (GA) in presence of NaCl at 0.5 or 1%. The maximum IAA and GA production were obtained by FS12 isolate (4.32 and 4.52 mg/100ml) and by FW2 isolate (2.71 and 2.92 mg/100ml) at 0.5% and 1% NaCl, respectively. FS12 was selected as the most efficient isolate for plant growth regulators (PGR) production and identified as Aspergillus niger. Carbon and nitrogen sources were studiedfor PGR optimization by the tested strain. Whey and peptone were used as a sole carbon and nitrogen source, where increased the IAA and GA production about 15.4% and 71.3% as compared to control (basal medium).

Cellular destruction, phytohormones and growth modulating enzymes production by Bacillus subtilis strain BC8 impacted by fungicides

In vitro experiments were performed to ascertain the impact of kitazin, hexaconazole, metalaxyl and carbendazim on growth behaviour, enzymatic profile, ultrastructure, cell permeability and bioactive molecules of phosphate-solubilizing bacterium. Strain BC8 isolated from Brassica oleracea rhizosphere was characterized and identified as Bacillus subtilis by 16S rDNA sequencing (Accession no. MG028650) technique. Strain BC8 was unambiguously chosen due to its high tolerance capability to various fungicides and substantial production of plant growth regulators. The biomarker enzymatic assays (lipid peroxidation, lactate dehydrogenase) and oxidative stress (catalase) induced by fungicides exhibited significant (p < 0.05) toxicity of fungicides toward strain BC8. Fungicides caused the cellular/ultrastructural damage and reduced the viability of strain BC8 as clearly revealed under scanning (SEM), high resolution transmission (HR-TEM) and confocal laser scanning (CLSM) microscopy. As the concentration of fungicides increased, a gradual drop in the plant growth promoting traits of B. subtilis strain BC8 was observed. Kitazin at 2400 μg mL−1, hexaconazole at 1500 μg mL−1, metalaxyl at 1200 μg mL−1 and carbendazim at 1200 μg mL−1decreased the IAA production by 35 (48.3 μg mL−1), 27 (51.5 μg mL−1), 39 (43.6 μg mL−1) and 47% (37.3 μg mL−1), respectively, over control (71.3 μg mL−1), while, α-ketobutyrate was declined by 51 (29.6), 56 (26.2), 61 (22.8) and 68 (19)%, respectively, over untreated control (59.9 mg protein−1 h−1). Also, with increase in the concentration of fungicides there was a significant decrease in plant nutrient (P); the maximum being (19.6 μg mL−1) observed at 1500 μg mL−1 hexaconazole with consequent drop in pH (from pH 6.4 to 4.2). The current findings clearly suggest that despite injury, B. subtilis maintained secreting active biomolecules and this property makes this organism truly indispensable for enhancing crop production under fungicide stressed conditions.

Efficacy of Facultative Oligotrophic Bacterial Strains as Plant Growth-Promoting Rhizobacteria (PGPR) and their Potency Against Two Pathogenic Fungi Causing Damping-off Diseases

Plant growth promoting is a multitask phenomenon. The bacteria achieve this by suppressing plant pathogens, production of plant-growth regulators, fixing atmospheric nitrogen, and solubilizing phosphate and micronutrients. Therefore, the present study aimed to examine the facultative oligotrophic bacteria isolates as biocontrol and plant growth promoting agents. The test isolates (FNS1 and FNS2) possessed Plant Growth Promoting Rhizobacteria (PGPR) (abilities including Indole Acetic Acid (IAA) production, Salicylic acid (SA) production, zinc and phosphate solubilization, N2-fixation, cellulase and chitinase production) and potency against pathogenic fungi causing damping-off disease (Pythium ultimum and Rhizoctonia solani). Isolates were tested against high temperature, pH and salt tolerant characters which prevail in this region. Molecular identification by 16s rDNA and nucleotide sequencing was made for the test isolates. Snap bean (Phasolius vulgaris L. cv, Xera) plants were inoculated with bacterial isolates (FNS1 and FNS2) in presence of 1/3 Nitrogen (N)-recommended dose. Inoculated plants increased significantly in N-content and plants dry weight. The antagonizer strains together enhanced the level of defense principles like Peroxidase (PO), Polyphenol Oxidase (PPO) and Total phenol content of plants. Damping-off disease suppression was expressed as there was increase in the percentage of survived plants which were inoculated when compared with uninoculated plants. These results indicate that Bacillus thioparans and Stenotrophomonas maltophilia have growth promoting potential and can be tested at field level for investment as bioinoculant.

Metabolite and Mechanistic Basis of Antifungal Property Exhibited by Endophytic Bacillus amyloliquefaciens BmB 1.

Plants are ubiquitously colonized by endophytic microorganisms which contribute significantly to plant health through production of plant growth regulators or disease suppression. In the present study, an endophytic bacterial isolate designated as BmB 1 with significant antifungal and plant growth promoting properties was isolated from the stem tissue of Bacopa monnieri (L.) Pennell. The isolate was studied in detail for the molecular and chemical basis of its bioactivity which proved it to have the presence of surfactin, iturin, and type I polyketide synthase (PKS) genes. For the analysis of the chemical basis of antifungal property, extract of the isolate was initially checked for its activity on test pathogens and LC-MS/MS based analysis further confirmed the presence of bacillomycin (m/z (M+H(+)) 1031.8) and surfactin (m/z (M+H(+)) 1008.6 and 1022.6) in the extract prepared. The light microscopic and SEM analysis of the treated and untreated mycelia of the pathogens clearly revealed the hypal destruction caused by the compounds produced by the selected isolate. This confirms the ability of the organism to directly inhibit the growth of the tested pathogens. The GC-MS analysis also confirmed the isolate to have the presence of volatile compounds with the expected role to induce induced systemic resistance (ISR) of the plant. Because of the multitargeted antifungal property, the isolate which was identified as Bacillus amyloliquefaciens can have potential biocontrol applications.

Indole-3-acetic acid biosynthetic pathways in the basidiomycetous yeast Rhodosporidium paludigenum.

Microorganisms produce plant growth regulators, such as auxins, cytokinins and gibberellins, to promote plant growth. Auxins are a group of compounds with an indole ring that have a positive effect on plant growth. Indole-3-acetic acid (IAA) is a plant growth hormone classified as an indole derivative of the auxin family. IAA biosynthesis pathways have been reported and widely studied in several groups of bacteria. Only a few studies on IAA biosynthesis pathways have been conducted in yeast. This study aimed to investigate IAA biosynthesis pathways in a basidiomycetous yeast (Rhodosporidium paludigenum DMKU-RP301). Investigations were performed both with and without a tryptophan supplement. Indole compound intermediates were detected by gas chromatography-mass spectrometry. Indole-3-lactic acid and indole-3-ethanol were found as a result of the enzymatic reduction of indole-3-pyruvic acid and indole-3-acetaldehyde, in IAA biosynthesis via an indole-3-pyruvic acid pathway. In addition, we also found indole-3-pyruvic acid in culture supernatants determined by high-performance liquid chromatography. Identification of tryptophan aminotransferase activity supports indole-3-pyruvic acid-routed IAA biosynthesis in R. paludigenum DMKU-RP301. We hence concluded that R. paludigenum DMKU-RP301 produces IAA through an indole-3-pyruvic acid pathway.

Phenotypic and genotypic characterization of inhabitant PGPR strains of Pseudomonas from apple orchards

Aim of present research was to isolate and characterize the Pseudomonas strains phenotypically and genotypically from the rhizospheric soil of apple orchard at Maggota (Shimla district) Himachal Pradesh. Phenotypic identification of the test isolates was based on morphological, physiological and biochemical characterization of the bacteria followed by genotypic analysis using rRNA gene sequencing and RAPD-PCR analysis. The fourteen Pseudomonas sp. isolates were screened out for various plant growth promoting activities such as siderophore production, antifungal activity, phosphate solubilisation, HCN and ammonia production, production of plant growth regulators and lytic enzymes. Isolates showed production of plant growth regulators (auxins, gibberellins and cytokinins) in the range of 19.67-83.33?g/ml, 21.00-58.67 ?g/ml and 12.33-43.33 ?g/ml respectively. Pseudomonas strains showed phosphate solubilising activity in the range of 12.33-63.33 Pi ?g/ml, 53.66-93.44 % SU siderophore production and 11.33-96.33mm (diameter) protease activity in plate assay. Five Pseudomonas isolates i.e. An-16-kul, An-1-mag, An-2-mag, An-3-mag and An-6-mag showed maximum antifungal activity against plant pathogenic fungi. Therefore, the aim of present investigation was to study multifarious plant growth promoting qualities of Pseudomonas sp. and to select more efficient PGPR strain of fluorescent Pseudomonas sp. which can be further used as biofertilizer.