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To promote the growth of Casuarina equisetifolia and address the abnormalities in the structure and function of rhizosphere soil microbial community, we isolated eight strains with multiple functions from the root nodules of C. equisetifolia, including nitrogen fixation ( N), production of cell wall-degrading enzymes ( protease and cellu-lase), auxin ( IAA) production, siderophore production, ammonia ( NH3) production, and phosphate solubilization. Among these strains, LB08, LB18, LB19, LB42, LB46, LB63, and LB69 were identified as Paenibacillus species, while LQ10 was identified as a Brucella sp. Results of seed soaking experiments showed that all the eight strains promoted the growth of C. equisetifolia seedlings. Strain LB69 significantly increased the germination rate and seedling vigor by 19.7% and 28.3%, respectively. Strain LQ10 significantly enhanced root length and root vigor by 48.2% and 334.4%, respectively. Strains LB18 and LB42 had the strongest effects on early shoot length and biomass accumulation, with increases of 22.4% and 32.8%, respectively. After seed soaking, the number of isozymes bands of polyphenol oxidase, superoxide dismutase, and peroxidase increased, with some bands showing enhanced intensity and increased diversity of enzyme isoforms, thereby enhancing stress resistance. In summary, the addition of these eight strains promoted plant growth and antioxidant enzyme activity, indicating their potential role as biofer-tilizers. [ABSTRACT FROM AUTHOR]

The major research focus for biological nitrogen fixation (BNF) has mostly been on typical rhizobia with legumes. But the newly identified non-rhizobial bacteria, both individually or in combination could also be an alternative for nitrogen supplementation in both legumes and nonlegume plants. Although about 90% of BNF is derived from a legume – rhizobia symbiosis, the non-legumes specially the cereals lack canonical nitrogen fixation system through root-nodule organogenesis. The non-rhizobia may colonize in the rhizosphere or present in endophytic/associative nature. The non-rhizobia are well known for facilitating plant growth through their potential to alleviate various stresses (salt, drought, and pathogens), acquisition of minerals (P, K, etc.), or by producing phytohormones. Bacterial symbiosis in non-legumes represents by the Gram-positive Frankia having a major contribution in overall fortification of usable nitrogenous material in soil where they are associated with their hosts. This review discusses the recent updates on the diversity and association of the non-rhizobial species and their impact on the growth and productivity of their host plants with particular emphasis on major economically important cereal plants. The future application possibilities of non-rhizobia for soil fertility and plant growth enhancement for sustainable agriculture have been discussed. [ABSTRACT FROM AUTHOR]

Tubercle disease or a bacterial pocket disease of sugar beets are names used to describe one of the gall-malformed diseases of sugar beet roots. Xanthomonas beticola is the historical name of the pathogen supposedly causing bacterial pocket disease. There were no isolates deposited in any collection corresponding to the originally isolated bacteria, except two strains from the NCPPB (National Collection of Plant Pathogenic Bacteria, UK). However, both isolates were identified as related to Bacillus pumilus, which raised doubts about their pathogenicity. In our laboratory, greenhouse, and preliminary field experiments, we demonstrated that such strains are not pathogenic to sugar beets. Furthermore, both strains promoted their growth, improved their yield quality, and partly protected them against Rhizoctonia solani in a field experiment. [ABSTRACT FROM AUTHOR]

C1-microorganisms that can utilize C1-compounds, such as methane and methanol, are ubiquitous in nature, and contribute to drive the global carbon cycle between two major greenhouse gases, CO2 and methane. Plants emit C1-compounds from their leaves and provide habitats for C1-microorganisms. Among C1-microorganisms, Methylobacterium spp., representative of methanol-utilizing methylotrophic bacteria, predominantly colonize the phyllosphere and are known to promote plant growth. This review summarizes the interactions between C1-mircroorganisms and plants that affect not only the fixation of C1-compounds produced by plants but also CO2 fixation by plants. We also describe our recent understanding of the survival strategy of C1-microorganisms in the phyllosphere and the application of Methylobacterium spp. to improve rice crop yield. [ABSTRACT FROM AUTHOR]

The aim of this work was to isolate endophytic bacteria associated with roots, stems, leaves and panicles of rice varieties 2000, Tana, 473, 67 and to determine in vitro antimicrobial activity on Burkholderia glumae. The population density of endophytic bacteria was estimated by direct count on R2A medium. The antimicrobial activity of endophytic bacteria on B. glumae was determined by disc diffusion technique in King B culture media. Growth promoting capacity was determined by biological nitrogen fixation, phosphate solubilization, siderophore production. Extraction of microbial secondary metabolites was evaluated in vitro on B.glumae. Molecular identification of endophytic bacteria with antimicrobial activity was performed by sequencing technique from PCR products amplified with specific primers of eubacterial groups, bacteria with equal or higher percentage of inhibition were selected for DNA extraction and phylogenetic analysis. Differences between the population density (CFU/g tissue) of endophytic bacteria according to variety and tissue type were analyses by multifactorial ANOVA in the InfoStat programme. The multiple range test (Tukey) was also used to establish separate differences between communities of endophytic bacteria in relation to variety and type of colonized tissue. The multiple range test (Duncan) was also used to establish differences in inhibition percentages. A total of 107 isolates in the different rice varieties with the highest population density in variety 2000 and the lowest density in variety 67, the tissue with the highest colonization was the root. Of the isolates, 4 showed equal or higher in vitro antibacterial activity on B. glumae compared to the control, these also showed the ability to fix nitrogen, solubilize phosphate and produce siderophores. The sequencing results proved the identity of Bacillus thuringensis. It can be concluded that the population density of endophytic bacteria depends on the degree of susceptibility of the plant. In addition to this, the isolates showed an antagonistic effect on B.glumae which, in turn, have the ability to promote plant growth through phosphate solubilization, nitrogen fixation and siderophore production. Finally, the extraction of microbial secondary metabolites was not adequate, which was confirmed by in vitro evaluation giving a negative result. [ABSTRACT FROM AUTHOR]

Microorganisms can solve the global problem of arsenic (As) contamination in soil and water, by eliminating the hazardous metalloid from contaminated habitats. A native As-resistant PMM6 strain was isolated from the tainted agricultural field in Durgapur, India. Following phenotypic investigations, fatty acid methyl ester analysis, and 16S rDNA sequence-based homology, it was identified as Bacillus cereus. Various analytical techniques such as atomic absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy studies revealed a positive correlation between the strain's resistance properties against arsenate (75 mM) and arsenite (25 mM) and the biosorption and bioaccumulation of arsenic. The strain exhibited several important plant growth-promoting traits, including indole-3-acetic acid production (110.0±0.33μg/mL), 1-aminocyclopropane-1-carboxylate deaminase activity (2334.2±1.90 nm α-ketobutyrate/mg protein/h), phosphate solubilization, and siderophore production (68.0±2%). These traits facilitated the growth augmentation of rice seedlings under As stress, both in terms of physiological and biochemical parameters. Compared to uninoculated soil, the use of strain PMM6 helped to reduce As mobilization and oxidative stress in rice seedlings growing in As-spiked soil. Therefore, strain PMM6 holds the potential as bioremediator to restore As-contaminated agricultural lands while also promoting the growth of rice seedlings. It could thus be utilized in the bioremediation of As-contaminated agricultural lands in the near future. • A native arsenic-resistant rhizobacterium Bacillus cereus PMM6 was isolated from rice fields. • The strain showed a higher degree of resistance to both arsenite and arsenate. • PMM6 strain exhibited several PGPR traits including acc deaminase activity. • Biotransformation and bioaccumulation of As in PMM6 was confirmed from various in vitro studies. • PMM6 was found to promote rice seedling growth under arsenic-stressed conditions. [ABSTRACT FROM AUTHOR]

A plant growth-promoting endophytic strain Bacillus sp. WR11 produces high-level phytase. Phytase degrades phytate, which is the major form of organic phosphate in soils that cannot be readily utilized by plants. To strengthen the strain or its phytase for cost-efficient biodegradation of phytate, we compared the impacts of different chemical additives on phytase production and preservation. Phytate degradation ability in soils and growth promotion effect in wheat were evaluated. To ensure safe application, potential pathogenicity of the strain was also predicted. Phytase activity assay suggests that sodium alginate (SA) significantly improves phytase production to as higher as 2.21-fold, but has little influence on the growth of WR11 during liquid fermentation. During liquid storage of cell-free supernatant (CFS) at room temperature, SA maintains 68% phytase activity indicating significantly improved stability within four weeks. Determination of water-soluble P and phytate-P indicates Bacillus sp. WR11 and CFS effectively degrade 20.17–38.55% phytate in soils. Quantification of biomass, phosphorus and iron contents shows positive effect of WR11 and its CFS on wheat growth. Particularly, the degradation ability (63.2%) and growth promoting effect of CFS is much stronger in the presence of 0.8% SA. Genomic prediction demonstrates strain WR11 has a large number of genes in the databases of Pathogen-Host Interactions, Virulence Factors of pathogenic bacteria, Antibiotic Resistance Genes, and the Comprehensive Antibiotic Research Database, respectively. In conclusion, SA significantly improves phytase production and phytate degradation. Phytase accompanied with SA may be an alternative strategy for phytate degradation and plant growth promotion, when microorganisms have safety issues. • A plant growth-promoting endophytic strain Bacillus sp. WR11 produces high-level phytase. • Phytase production during fermentation can be improved by sodium alginate. • Sodium alginate keeps phytase stable in the cell-free supernatant. • Sodium alginate enhances soil phytate degradation and phosphorous utilization. [ABSTRACT FROM AUTHOR]

Among the major constraints for the production of economic crops, such as maize, is salinity. Plenty of research has suggested the use of various strains of plant growth-promoting rhizobacteria (PGPR) as a sustainable approach to improve plant tolerance to salinity. Nonetheless, the exploration of the rhizosphere in Egyptian agricultural lands with salt affected soil remains incomplete. In this research, two newly isolated local bacterial species were finally selected and identified as Alcaligenes sp. strains. E1 (BS-45) and E2 (BS-57). IAA production by both isolates was confirmed by TLC. Several bioactive metabolites were identified in Alcaligenes sp. E1 and E2 by gas chromatography-mass spectroscopy (GC-MS). These include 9,12,15-octadecatrienoic acid, 2,3-bis [(trimethylsilyl)oxy] propyl ester, (z,z,z), 2 (1H)-Naphthalenone, octahydro-1-methyl-1-(2-propenyl)-, (1à,4aá,8aà), dodecane and isopulegol which have a defensive role against biotic and abiotic stress of the plant. Interestingly, the selected bacteria Alcaligenes sp. E1 and E2 significantly improve the overall maize growth attributes, antioxidant scavenging activities and photosynthetic pigments in maize plants grown under salt stress (150 mM NaCl) compared to the control plants as analyzed by greenhouse experiment. Therefore, this study recommends the Alcaligenes sp. strains (E1 and E2) to alleviate the negative impact of salinity on the growth and development of maize seedlings. • Two potent native soil bacterial isolates were selected based on plant growth promoting and antifungal activities. • The selected isolates were identified as Alcaligense sp. E1 and Alac ligense sp. E2. • The bacterial cultural and nutritional conditions for IAA production were optimized. • The prospective bioactive compounds have been detected and identified by gas chromatography-mass spectroscopy. • Significant improvement in growth of maize seedling under high-salt stress were recorded compared to untreated control. [ABSTRACT FROM AUTHOR]

The success of the sodic soil reclamation using elemental S (S°) depends on the population of the native S° oxidizers. Augmenting the native flora of the sodic soils with effective S° oxidizers can enhance the success of the sodic soil reclamation. Present study reports for the first time the S° oxidation potential of the Sphingomonas olei strain 20UP7 isolated from sodic soils with pH s 9.8 and EC e 3.6 dS m–1. Inoculation with S. olei strain 20UP7 caused 13.0–24.2 % increase in S° oxidation in different sodic soils (pH s 9.1–10.5). It improved the concentration of the Ca2+, Mg2+, PO 4 3– and declined the HCO 3 – and total alkalinity of the soil solution. This isolate also showed appreciable P and Zn solubilization, indole acetic acid, ammonia, and titratable acidity production in the growth media. It tended to the formation of biofilm around sulphur particles. The PCR amplification with gene–specific primers showed the occurrence of soxA , soxB , and soxY genes with a single band corresponding to length of 850, 460, and 360 base pairs, respectively. The integration of the S. olei strain 20UP7 with S° caused 21.7–25.4 % increase in the rice and wheat yield compared to the soil treated with S° alone. This study concludes that the S. olei, native to high saline–sodic soils can be utilized for improving the sodicity reclamation and plant growth promotion using elemental S based formulations. [Display omitted] • Haloalkaliphilic Sphingomonas olei strain20UP7 posses Sox S–oxidation enzyme system • S. Olei inoculation increased S–oxidation by 13–24 % in soils of pH s 9.8–10.5 • Inoculation of SOB increased productivity of rice–wheat by 21.7–25.4 % • SOC, Cl–, and Ca2+ content in soil solution controlled the response of inoculation [ABSTRACT FROM AUTHOR]

This study investigated the impact of a mixture of six endophytic bacterial strains isolated from cucumber plants on the growth and microbiome diversity of six cucumber traditional varieties and hybrids. Six bacterial species were isolated and identified by 16 s rRNA sequencing. All the bacteria showed plant growth promoting traits. Bacillus tequilensis showed 80 % inhibition of the mycelia growth of Fusarium oxysporum f.sp. cucumarinum (Foc). Mixed culture of all the bacteria was prepared and applied back to the varieties and hybrids of cucumber plants through seed soaking. Plant growth characteristics indicated that the treated plants showed increased plant growth in terms of plant height, number of leaves, vine length, male:female flower ratio, number of fruits and fruit length. Bacteria treated plants of hybrid HiVeg Chitra recorded 19 cm increase in vine length compared to control plants. The matataxonomic analysis of leaf samples by Illumina sequencing highlighted a diverse bacterial community shift in treated plants, with significant increases in genera like Bacillus and Staphylococcus. The core microbiome analysis identified key genera such as Bacillus, Staphylococcus, Sphingomonas, Methylobacterium , etc that could be pivotal in plant growth promotion. Bacillus and Staphylococcus showed increased abundance in treated varieties, correlating with the observed in plant growth parameters thus indicating their role in growth promotion of cucumber plants. Endophytic bacterial species identified from cucumber plants when re-applied by seed soaking, they promote the plant growth by modulating the microbiome. The bacterial species identified in the study could be potential candidates as microbial bioinputs for cucumber cultivation. [ABSTRACT FROM AUTHOR]

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Trichoderma fungi are considered as suitable biofertilizers, since they could increase the efficiency of the use of nutrients in plants and are used as biocontrol agents against plant pathogen. The aim of this study was to characterize a set of Trichoderma strains isolated from horticultural and near-pristine soils from the Argentine Pampas, and to evaluate their potentiality as a growth promoter and as a biocontroller of Fusarium wilt disease on tomato. Nineteen collected strains, identified as T. brevicompactum, T. gamsii and T. harzianum , were tested for their ability to produce the auxin indole 3-acetic acid (IAA), solubilize phosphate and biocontrol F. oxysporum. Twelve strains reduced growth of pathogenic fungus over 50% and four of them (named FCCT 16, FCCT 58, FCCT 199-2 and FCCT 363-2) exhibited IAA highest production (ranging 13.38–21.14 µg/ml) and were able to solubilize phosphate (ranging 215.80–288.18 µg/ml of calcium phosphate). Tomato plants inoculated with those four strains increased chlorophyll content, shoot length, fresh and dry weight of shoot and roots, and reduced F. oxysporum wilt disease between 10 and 30%. On the basis of our results, we conclude that soils of the Argentine Pampas harbor Trichoderma strains with beneficial dual effects which could be of interest for the development of commercial products. [ABSTRACT FROM AUTHOR]

In the present study, a potent Aluminum (Al) resistant yeast strain CAM4 was isolated from rhizosphere soil of Rubus geoides, grown in acidic Andisols and identified as Rhodotorula mucilaginosa by 18S rRNA gene sequence analysis. The strain CAM4 was selected in terms of abiotic stress tolerance to Al, salinity and drought with multiple plant growth promoting (PGP) traits. Besides, strain CAM4 also exhibited Al removal efficiency (80–88%) from the culture medium even under combined stresses of salinity and drought. The sawdust-based formulation of strain CAM4 (sawdust-molasses 5%-PEG 1%-strain CAM4) showed higher cell viability of up to 24 weeks (8.54 log CFU g−1). Inoculation of formulated strain CAM4 significantly enhanced the various morphological and biochemical characters of Lactuca sativa grown under abiotic stress conditions. The formulated strain CAM4 also reduced the accumulation of Al in L. sativa as well that conferring Al tolerance to the plants. The study concludes that strain CAM4 could be used as a biofertilizer for healthy and safe crop production in soils, with Al toxicity as well as combined salt and drought stresses. • R. mucilaginosa strain CAM4 showed tolerance to Al, salinity and drought stresses. • It possessed important PGP traits even under abiotic stress conditions. • Bioaccumulation of Al by a R. mucilaginosa strain CAM4 was confirmed. • Strain CAM4 improved the growth of L. sativa under abiotic stress conditions. • It also reduced oxidative stress and Al uptake in L. sativa plants. [ABSTRACT FROM AUTHOR]

Globally more than 5.2 billion hectares of farming fields are damaged through erosion, salinity and soil deterioration. Many salt stress tolerant bacteria have plant growth promoting (PGP) characteristics that can be used to overcome environmental stresses. Isolation and screening of salt-tolerant endophytes from Salicornia brachiata were achieved through surface sterilization of leaves followed by cultivation on 4% NaCl amended media. Performance of isolates towards indole-3-acetic acid (IAA) production, phosphate solubilization, ACC deaminase activity, ammonia production, siderophore production and stress tolerance were determined. On the basis of the highest plant growth promoting activity, SbCT4 and SbCT7 isolates were tested for plant growth promotion with wheat and maize crops. In the present study, a total of 12 morphologically distinct salt-tolerant endophytic bacteria was cultured. Out of 12 isolates, 42% of salt-tolerant endophytes showed phosphate solubilization, 67% IAA production, 33% ACC-deaminase activity, 92% siderophore production, 41.6% ammonia production and 66% HCN production. A dendrogram, generated on the basis of stress tolerance, showed two clusters, each including five isolates. The bacterial isolates SbCT4 and SbCT7 showed the highest stress tolerance, and stood separately as an independent branch. Bacterial isolates increased wheat shoot and root dry weights by 60-82% and 50-100%, respectively. Similarly, improved results were obtained with maize shoot (27-150%) and root (80-126%) dry weights. For the first time from this plant the bacterial isolates were identified as Paenibacillus polymyxa SbCT4 and Bacillus subtilis SbCT7 based on phenotypic features and 16S rRNA gene sequencing. Paenibacillus polymyxa SbCT4 and B. subtilis SbCT7 significantly improved plant growth compared to non-inoculated trials. [ABSTRACT FROM AUTHOR]

Abstract Considerable evidence exists that microorganisms play a significant role in the remediation of soil contaminated with heavy metals. Aspergillus aculeatus (A. aculeatus) isolated from Cd-polluted soil has been shown to increase the tolerance of turfgrasses to Cd stress. In this study, we assessed the tolerance, biosorption capacity for Cd and surface characteristics of this fungus and investigated the effect of plant inoculation with A. aculeatus on the lipid peroxidation, antioxidant activities and photosynthetic rates in rice cultivated in Cd-contaminated soil. The results indicated that the removal efficiency of A. aculeatus was 46.8% at a Cd concentration of 10 mg L−1. The A. aculeatus strains had the capacity to produce indole acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase and to solubilize phosphate. The O 2 - accumulation and the amount of MDA in rice roots inoculated with A. aculeatus were significantly lower than those in uninoculated plants. Nevertheless, no decrease in leaf ROS accumulation and photosynthetic activity was observed between the inoculated and uninoculated plants. Inoculation with A. aculeatus contained more of the ROS-scavenging metabolite GSH, a higher GSH/GSSG ratio, and higher antioxidative enzyme (SOD, POD, and CAT) activities, possibly explaining the lower ROS concentrations observed in inoculated roots in the presence of Cd. These results suggest that application of A. aculeatus has the potential to protect crops against Cd stress. Graphical abstract fx1 Highlights • aculeatus has extremely high tolerance and removal efficiency for Cd. • The fungus protected rice against the inhibitory effects of Cd. • It facilitated rice growth by synthesis of bioactivator growth regulator. • It provided a physical barrier against Cd uptake into plant root. [ABSTRACT FROM AUTHOR]

Abstract Wheat straw is a major lignocellulosic waste produced in agricultural processes and has been traditionally used as soil conditioners in the form of compost, a precursor for humus. Microorganisms play an important role in the conversion of organic waste into plant available nutrients. Thus, it is essential to isolate the potential microorganisms from rotten/decomposed agricultural waste like wheat straws and endowed the plant growth promotion (PGP) as well as antagonism behavior against phyto-pathogens. The current study was conducted to investigate the actinobacteria isolated from rotten wheat straw for PGP and antagonistic traits. Among the all isolates, three strains (UU07, UU11 and UU15) were screened and were found potential to plant growth promoting (PGP) traits (IAA, siderophore, phosphate solubilization, HCN, ammonia and AAC deaminase). Based on 16S rRNA gene sequencing, isolates were identified as Streptomyces rochei UU07, Streptomyces vinaceusdrappus UU11 and Streptomyces sp. UU15. Strain UU07 showed 6.0% tolerance to salt and grew well at pH 4.5–9.4, while UU11 and UU15 were moderately tolerant to salt and pH. They grew well at 28 °C but were unable to grown on temperature above 45 °C. Seedling assay and antagonism test of S. rochei UU07 revealed it as one of the best PGP strain and potential antagonist for Rhizoctonia solani. These results confirmed that rotten wheat straw can serve as a potential source for isolation of actinobacteria with PGP traits which could further be used as consortia for composting of different agriculture-waste and increase crop production. Highlights • Streptomyces were isolated from rotten wheat straw. • Screened isolates were potential to tolerate the abiotic stress as salt, pH and temperature. • Tested strains were able to potential plant growth promotion and antagonistic activity. [ABSTRACT FROM AUTHOR]

Abstract The increasing demand of the agricultural produce can be attained by optimizing the productivity potential and by minimizing the losses caused by notorious plant-parasitic nematode of the crops. Chemical based nematode control is an effective strategy to combat this biotic stress, but inappropriate and inadequate application of synthetic pesticides has exerted an adverse effect on bio-flora, fauna and natural enemies. Due to the environmental and regulatory pressure, use of potential biocontrol agents is the most welcomed way for nematode management by the farming community. There is an emerging market for Plant growth promoting rhizobacteria (PGPR) mediated eco-friendly biopesticides for plant-parasitic nematode biocontrol. Moreover, PGPR strains can enhance the plant growth through the production of various plant growth promoting substances. Based on the fact stated above, the present review focused on PGPR based nematodes biocontrol strategies, the direct and indirect mechanism of PGPR for nematode biocontrol and future prospect of PGPR based biocontrol agents against nematodes are discussed. [ABSTRACT FROM AUTHOR]

Endophytic microbes coexist inside the plant without causing any negative impact on host. Endophytic microbes including bacteria and fungi represent huge diversity in the plants of Himalayan region with immense economic importance. Since ages, medicinal plants like Ocimum sanctum , Cinnamomum camphora, Arnebia euchroma, Taxus wallichiana, Picrorhiza kurroa (Kutki) and Pinus roxburghii are used in Ayurveda due to high curative properties. Endophytes present in these plants have been found to be associated with plant growth-promoting activities as well as therapeutic properties such as antimicrobial, anti-fungal, anti-inflammatory, and antiseptic. Some endophytic microbes isolated from plants of Himalayan region are documented to produce different bioactive compounds of therapeutic interest. The species of microbes are; Tolypocladium niveum, Cylindrocarpon lucidum , Enterobacter cloacae , Alternaria alternata, Pseudomonas, Bacillus sp., etc. All have caliber to synthesize various compounds of medicinal interest against various diseases like respiratory, gastrointestinal, and skin diseases as well as repair of oncogenic cells. Therefore, it is of key significance to focus on researches pertaining to enhancement of bioactive potential in view of human health. Through a web search using the keywords "endophytes harboring in medicinal plants of Himalyan region" or "Himalayan region endophytes with their medicinal properties," we have succinctly summarised the various medicinal plants and their endophytes residing the plants of Himalayan region with their medicinal significance in the present review. Here, we have comprehensively discussed the diversity of endophytic microbes including bacteria and fungi present in the plants and their medicinal properties to cure severe human diseases. • The biodiversity of Himalayas • Medicinal plants. • Endangered medicinally important plants of Himlayan region • Plant growth promoting microbes. • Endophytes • Human health [ABSTRACT FROM AUTHOR]

Plant growth and yield characteristics of black pepper ( Piper nigrum L.) on inoculation with the root endophytic fungus Piriformospora indica are reported. Experiments were carried out using plants raised from the lateral branches of black pepper which develop into miniature plants known as “bush pepper” that bear fruits in the same year of planting. P. indica ( Pi ) inoculated plants put forth more number of leaves and leaf area per plant compared to the control plants throughout the period of the experiment. There was significant difference between the inoculated and uninoculated plants with respect to the chlorophyll a and total chlorophyll content of leaf tissues. Early flowering and spike setting was observed in plants inoculated with Pi . The total fresh and dry weights of berries harvested from the Pi inoculated plants were significantly higher than that from the control plants. Inoculation with the fungus also increased the total oleoresin and piperine content in the berries. [ABSTRACT FROM AUTHOR]

Biological control of plant diseases is strongly emerging as an effective alternative to the use of chemical pesticides and fungicides. Stress tolerance is an important attribute in the selection of bacteria for the development of microbial inoculants. Fourteen salt-tolerant bacteria showing different morphological features isolated from the rhizosphere of maize were evaluated for different plant growth-promoting activities. All isolates showed auxin production ranging from 5 to 24 µg · ml-1 after 48 h incubation in tryptophan supplemented media. Phosphate solubilization ranged from 15 to 419 µg · ml-1. 1-aminocycloproprane-1-carboxylate (ACC) deaminase activity was shown by 6 isolates, ammonia production by 9 isolates, siderophore production by 8 isolates while HCN production by 4 isolates. Four bacterial isolates with all plant growth-promoting properties also showed strong antagonistic activities against Fusarium oxysporum, F. verticillioides, Curvularia lunata and Alternaria alternata and abiotic stress tolerance against salinity, temperature, pH and calcium salts. Two selected bacterial isolates significantly enhanced the growth of pea and maize test plants under greenhouse conditions. The bacterial isolate M1B2, which showed the highest growth promotion of test plants, was identified as Bacillus sp. based on phenotypic and 16S rDNA gene sequencing. The results indicated that Bacillus sp. M1B2 is a potential candidate for the development of microbial inoculants in stressful environments. [ABSTRACT FROM AUTHOR]

The endophytic bacteria isolated from the leaves, stems, tubers and roots of Helianthus tuberosus L. (Jerusalem artichoke) were studied and characterized. The isolated endophytes were clustered by amplified ribosomal DNA restriction analysis (ARDRA) technique and identified by 16 S rRNA sequencing to demonstrate bacteria diversity, mainly in Bacillus , Pseudomonas , Stenotrophomonas , Microbacterium , Curtobacterium . The proportions of endophytes exhibited colonization (from most to least) in stems, leaves, roots and tubers. The more isolates had ACC (1 aminocyclopropane-1-carboxylate) deaminase and nitrogen fixation, the less they showed phosphate and potassium solubilization. Antifungal activity was exhibited only in Bacillus , while many isolates had stress tolerance in polyethylene glycol. Six endophytic bacteria were recolonized into 2 varieties of Jerusalem artichoke (HEL65 and JA102xJA89) and showed increases in height, root and stem weight, and tuber number. The potential local endophyte, Pantoea ananatis 4.14 responded to the tuber by increasing inulin content, which is a valued product of Jerusalem artichoke. [ABSTRACT FROM AUTHOR]

Fungal endophytes can be considered as a new source of biological control and plant growth promoting agents. Moreover, the huge repertoire of extracellular enzymes produced by them has great biotechnological importance in medicine, agriculture and industry. The current study aimed at the assessment of plant growth promotion and biocontrol potential of endophytic fungal isolates associated with Dioscorea bulbifera L. for efficiently improved plant growth and protection of hosts from various infections. Overall, the experimental work revealed significant results where, 81% of the endophytic fungal isolates exhibited biocontrol potential against atleast one or more bacterial pathogens. The endophytic fungal isolate ARW2 (Clonostachys pseudochroleucha) was found to be highly effective against Gram positive bacteria whereas N4 (Parathyridaria percutanea) and H1B (Curvularia lunata) were effective against Gram negative bacteria. 52% of the endophytic fungal isolates were found to possess strong inhibition potential against fungal pathogens. H22 (F. proliferatum) and G8 (F. equiseti) demonstrated strong inhibition potential with percent inhibition ranging from 50 to 70%. The plant growth promoting activity of endophytic fungal isolates depicted that 52%, 27% and 2% isolates were capable of siderophore production, phosphate solubilisation and HCN production respectively. A quantitative estimation of IAA production revealed that almost all the isolates were producing IAA ranging from 1.2 to 200 μg/mL. Further assessment of extracellular enzymatic potential revealed that 37.5%, 31%, 18%, 12.5% and 4% of the endophytic fungal isolates exhibited activity positive results for amylase, lipolytic, protease, cellulolytic and chitinase activity, respectively. Our results indicate that these endophytic fungal isolated can be a promising source for future applications in medicine, agriculture and industry. • First report on exploration of biocontrol, plant growth promotion and extracellular enzymatic potential of fungal endophytes of D. bulbifera L. • Fungal endophytes were highly effective against bacterial and fungal pathogens. • Aspergillus fumigatus was reported to be more sensitive to the antagonists. • Profound results for plant growth promotion and extracellular enzymatic potential were observed. • These endophytes can be an alternative source in industry and agriculture. [ABSTRACT FROM AUTHOR]

The occurrence and role of endophytic bacterial communities in banana under different field-grown conditions have not yet been explored. Hence, a survey was conducted in five different banana cultivars – Rasthali, Hill banana, Co1, Nattu Poovan and Red banana – for the assessment of bacterial endophytes grown in Tamil Nadu, Southern India. From 352 endophytes isolated, 17 were selected based on distinct morpho-physiological characters. The 17 selected isolates were grouped into eight different genera, which belong to the phyla Actinobacteria, Firmicutes and Proteobacteria, with remarkable differences in the bacterial compositions among the banana cultivars. Higher bacterial diversity was observed in Rasthali and Red banana when compared to Co1 and Nattu Poovan. Isolates exhibited at least one functional plant growth-promoting trait when tested for siderophore production and indole-3-acetic acid (IAA) synthesis. Representative isolates from eight different genera were further analyzed for plant–microbe interactions. A seedling inoculation experiment on tomato showed a significant effect on seed germination, seedling growth, vigor index, and biomass production compared to the uninoculated control. However, a comprehensive approach is needed to evaluate the full potential of bacterial endophytes to improve quality and yield in banana under field conditions. [ABSTRACT FROM PUBLISHER]

The present study highlights the importance of cyanobacteria in plant growth promotion and screened the effect of biomass wet extract (BWE 1% and BWE 10%) of twenty cyanobacterial strains on the morphometric parameters of Pisum sativum L. seedlings after germination. Cyanobacterial BWE treatment significantly increased the radicle, plumule and total seedling length along with percentage of response than the control treatment with water. At BWE 1% treatment, Scytonema bohneri MBDU 104 showed 73.3% of the total seedling response, whereas Dolichospermum spiroides MBDU 903 showed increased total seedling length of 5.69 cm among other strains tested. All the tested strains varied among themselves at different parameters. To identify the most potent isolate, all the tested morphometric parameters were evaluated using a multi – criteria decision analysis (MCDA) of PROMETHEE-GAIA software. The isolate Scytonema bohneri MBDU 104 was selected as the potent plant growth promoting cyanobacteria and its BWE was purified using preparative – HPLC and analysed by LC-MS/MS for identifying possible plant growth elicitors. Phytohormones like indole-3 acetic acid (IAA), indole-3 butyric acid (IBA) and cinnamic acid along with free volatile fatty acids were identified and implicated for plant growth promotion by cucumber seed germination bioassay. [ABSTRACT FROM AUTHOR]

Plant associated bacteria are promising alternatives to chemical fertilizers for plant growth and yield improvement in an eco-friendly manner. In this study, rice associated bacteria were isolated and assessed for mineral phosphate solubilization and indole-3-acetic acid (IAA) production activity in vitro . Six promising strains, which were tentatively identified as phylotaxon Pseudochrobactrum sp. (BRRh-1), Burkholderia sp. (BRRh-2), Burkholderia sp. (BRRh-3), Burkholderia sp. (BRRh-4), Pseudomonas aeruginosa (BRRh-5 and BRRh-6) based on their 16S rRNA gene phylogeny, exhibited significant phosphate solubilizing activity in National Botanical Research Institute phosphate growth medium, and BRRh-4 displayed the highest phosphate solubilizing activity, followed by BRRh-5. The pH of the culture broth declined, resulting in increase of growth rate of bacteria at pH 7, which might be due to organic acid secretion by the strains. In presence of L -tryptophan, five isolates synthesized IAA and the maximum IAA was produced by BRRh-2, followed by BRRh-1. Application of two most efficient phosphate solubilizing isolates BRRh-4 and BRRh-5 by root dipping (colonization) of seedling and spraying at the flowering stage significantly enhanced the growth and grain yield of rice variety BRRI dhan-29. Interestingly, application of both strains with 50% of recommended nitrogen, phosphorus and potassium fertilizers produced equivalent or higher grain yield of rice compared to the control grown with full recommended fertilizer doses, which suggests that these strains may have the potential to be used as bioinoculants for sustainable rice production. [ABSTRACT FROM AUTHOR]

Agricultural sites irrigated for long term with water polluted by industrial effluents containing heavy metals might adversely affect the soil microbial communities and crop yield. Hence it is important to study rhizobacterial communities and their metal tolerance in such affected agricultural fields to restore soil fertility and ecosystem. Present work deals with the study of rhizobacterial communities from plants grown in copper (Cu) contaminated agricultural fields along the industrial zone of Gujarat, India and are compared with communities from a Cu mine site. Microbial communities from rhizosphere soil samples varied in the magnitude of their Cu tolerance index indicating differences in long term pollution effects. Culture dependent denaturing gradient gel electrophoresis (CD-DGGE) of bacterial communities revealed the diverse composition at the sampling sites and a reduced total diversity due to Cu toxicity. Analysis of 16S rRNA gene diversity of Cu tolerant rhizobacteria revealed the predominance of Enterobacter spp. and Pseudomonas spp. under Cu stress conditions. Cu tolerant bacterial isolates that were able to promote growth of mung bean plants in vitro under Cu stress were obtained from these samples. Cu tolerant rhizobacterium P36 identified as Enterobacter sp. exhibited multiple plant growth promoting traits and significantly alleviated Cu toxicity to mung bean plants by reducing the accumulation of Cu in plant roots and promoted the plant growth in CuSO 4 amended soils. [ABSTRACT FROM AUTHOR]

Trichoderma is one of the most studied and applied fungal biocontrol agents. The benefits of these microorganisms to the plant include: suppression of pathogens, growth promotion, enhanced nutrient availability and induction of resistance. The biological activity is related to the variety of metabolites that they produce. These metabolites have been found to directly inhibit the pathogens, increase disease resistance and enhance plant growth. In this study, we have examined the effect of two Trichoderma strains and their secondary metabolites on Vitis vinifera in terms of induction of disease resistance, plant growth promotion and increase of polyphenols or antioxidant activity in the grapes. Applications of T. harzianum M10 or T. atroviride P1, as well as their respective major secondary metabolites, harzianic acid (HA) and 6-pentyl-α-pyrone (6PP), have been conducted in greenhouse by foliar spray or drenching. The treatments suppressed the development of powdery mildew caused by Uncinula necator . In a field experiment, a spore suspension of T. harzianum strain T22 or a 6PP solution was applied until fruit harvest. The results indicated that both T. harzianum T22 and 6PP are able to improve crop yield and increase the total amount of polyphenols and antioxidant activity in the grapes. The effects of the isolated natural compounds were comparable with those obtained by using the living fungus. [ABSTRACT FROM AUTHOR]

In the present study, two plant growth promoting rhizobacteria (PGPR) strains of Streptomyces griseus (KAI-26 and MMA-32) and one PGPR strain of S. albus (KAI-27) were screened for their ability to bio-synthesize silver nanoparticles (AgNPs) and evaluated for their growth promotion in chickpea. The formation of Streptomyces- mediated biogenic AgNPs was confirmed through UV–visible spectrophotometer, Dynamic Light Scattering (DLS), Zetapotential, Fourier Transforms Infrared (FTIR) spectroscopy and Transmission Electron Microscope (TEM) analysis. In greenhouse, the biogenic AgNPs followed by Streptomyces strains significantly increased plant growth promoting traits and nitrogen fixation over the untreated plants. Defense enzymes, namely ascorbate peroxidase, catalase, phenylalanine ammonia lyase, polyphenol oxidase and superoxide dismutase were also found higher in the selected Streptomyces and biogenic AgNPs treated chickpea plants. The bio-fortification studies carried out by inductively coupled plasma-optical emission spectroscopy (ICP-OES) revealed a significant enhancement of Fe, Zn, Mn and K contents in the harvested chickpea grains that were treated with the Streptomyces strains and biogenic AgNPs over the untreated plants. The results of the present study, further aids in the efficient utilization of the selected PGPR and their biogenic AgNPs as better delivery agents in agriculture. [Display omitted] • Biosynthesis of AgNPs from Streptomyces griseus and S. albus. • Synthesized biogenic AgNPswere characterized by DLS, FTIR, and TEM analysis. • Streptomyces strains showed significant anti-fungal activity. • Greenhouse experiments conducted using Streptomyces strains and biogenic AgNPs. • Streptomyces , AgNPs enhanced chickpea PGP traits, antioxidants, and grain nutrients. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a toxic metalloid which pollutes soil and water, and negatively affects the growth and development of plants at different levels. This study investigated the effects of As-resistant and plant growth promoting (PGP) bacterial consortia on the germination and growth attributes of two cultivars (Swarna and MTU 1010) of rice (Oryza sativa L.) under As-flooded environment. The consortium consisted of five bacterial strains; Bacillus nealsonii strain ARP2, Pseudomonas nitritireducens strain ARP3, Exiguobacterium aestuarii strain ARRP3, Bacillus tequilensis strain ART2 and Microbacterium paraoxydans strain ADT5, which were isolated from different regions of Chhattisgarh, India. Soils inoculated with the bacterial consortia and supplemented with As(V)/As(III) were used to grow rice seeds under in vitro conditions. The results ascertained that the seedlings inoculated with the bacterial consortia grew well even in the presence of As, which was marked by increased shoot and root length, biomass, and total chlorophyll content. Further, inoculation of bacterial consortia reduced the oxidative stress to a significant level by up-regulating the expressions of protective genes encoding antioxidant enzymes. This consortium could decrease the As accumulation in plants upon successful colonization in the rhizosphere, suggesting possible exploitation of it for enhanced growth of plants and in the remediation of As-contaminated soils. [Display omitted] • Inoculation with five bacterial consortium alleviated the toxic effects of As in Oryza sativa L. • Presence of bacterial strains in the soil limit the uptake of As in seedlings. • Bacterial strains successfully colonized the root surface of plants. • Up-regulation of the expressions of protective genes encoding antioxidant enzymes was observed. • Application of As-resistant PGP bacterial consortium can improve productivity and nutritional values. [ABSTRACT FROM AUTHOR]

The current study focuses on plant promoting and metal detoxifying properties of a heavy metal resistant bacterium with phosphate (P) solubilizing and Indole-3-acetic acid (IAA) producing capabilities. The bacterium was a strain of Pseudomonas putida Ws3 selected from an agricultural land irrigated with sewage water. It could solubilize P up to 300 mg/l and produce IAA up to 200 µg/l in seven days at optimal culture condition, i.e. NaCl (0.5%), KCl (0.01–0.04%), Mg/Cl 2 (0.3%) and NH 4 Cl (0.5%) and 30 °C. Regarding soluble P and IAA concentrations in Pikovskaya (PVK) liquid media, the activity of the bacterium declined in media containing CuCl 2 (500 mg/l), PbCl 2 (300 mg/l) or CdCl 2 (300 mg/l). The metals at elevated levels limited the bacterial population growth in a soil-like substrate supporting roots of a model plant (maize or Zea mays ). Weekly bacterial inoculation to the substrate for 40 days alleviated the condition for plant growth, led to increased plant dry weight and decreased the metals accumulated in plant with large effect sizes in the shoot (g=1.49) and root (g=1.36). [ABSTRACT FROM AUTHOR]

Pantoea agglomerans, a gammaproteobacterium of plant origin, possesses many beneficial traits that could be used for the prevention and/or treatment of human and animal diseases, combating plant pathogens, promotion of plant growth and bioremediation of the environment. It produces a number of antibiotics (herbicolin, pantocins, microcin, agglomerins, andrimid, phenazine, among others) which could be used for combating plant, animal and human pathogens or for food preservation. Japanese researchers have demonstrated that the low-molecular-mass lipopolysaccharide of P. agglomerans isolated by them and described as 'Immunopotentiator from Pantoea agglomerans 1 (IP-PA1)' reveals the extremely wide spectrum of healing properties, mainly due to its ability for the maintenance of homeostasis by macrophage activation. IP-PA1 was proved to be effective in the prevention and treatment of a broad range of human and animal disorders, such as tumours, hyperlipidaemia, diabetes, ulcer, various infectious diseases, atopic allergy and stress-induced immunosuppression; it also showed a strong analgesic effect. It is important that most of these effects could be achieved by the safe oral administration of IP-PA1. Taking into account that P. agglomerans occurs commonly as a symbiont of many species of insects, including mosquitoes transmitting the Plasmodium parasites causing malaria, successful attempts were made to apply the strategy of paratransgenesis, in which bacterial symbionts are genetically engineered to express and secrete anti-Plasmodium effector proteins. This strategy shows prospects for a successful eradication of malaria, a deadly disease killing annually over one million people, as well as of other vector-borne diseases of humans, animals and plants. Pantoea agglomerans has been identified as an antagonist of many plant pathogens belonging to bacteria and fungi, as a result of antibiotic production, competition mechanisms or induction of plant resistance. Its use as a biocontrol agent permits the decrease of pesticide doses, being a healthy and environmental-friendly procedure. The application of the preparations of this bacterium efficiently protects the stored pome, stone and citrus fruits against invasion of moulds. P. agglomerans strains associated with both rhizosphere and plant tissues (as endophytes) efficiently promote the growth of many plants, including rice and wheat, which are the staple food for the majority of mankind. The promotion mechanisms are diverse and include fixation of atmospheric nitrogen, production of phytohormones, as well as degradation of phytate and phosphate solubilizing which makes the soil phosphorus available for plants. Accordingly, P. agglomerans is regarded as an ideal candidate for an environmental-friendly bioinoculant replacing chemical fertilizers. It has been documented that the Pantoea strains show biodegradation activity on various chemical pollutants of soil and water, including petroleum hydrocarbons and toxic metals. P. agglomerans prevents the penetration of harmful industrial contaminants into deeper parts of soil by biofilm formation, and has an ability to produce hydrogen from waste. Thus, this bacterium appears as a valuable bioremediator which, in some cases, may be acquired as a cheap form of energy. In conclusion, in spite of the proven pathologic role of P. agglomerans in causing occupational diseases of allergic and/or immunotoxic background and accidental infections, the beneficial traits of this species, and of related species of Pantoea genus, are of great value for potential use in many areas of biotechnology. Hence, any restrictions on the use of these organisms and their products should be declined, providing safety precautions at work with the Pantoea biopreparations are maintained. [ABSTRACT FROM AUTHOR]

The composition of root exudates is modulated by several environmental factors, and it remains unclear how that affects beneficial rhizosphere or inoculated microorganisms under heavy metal (HM) contamination. Therefore, we evaluated the transcriptional response of Pseudomonas putida E36 (a Miscanthus x giganteus isolate with plant growth promotion-related properties) to Cd, Pb and Zn in an in vitro study implementing root exudates from M. x giganteus. To collect root exudates and analyse their composition plants were grown in a pot experiment under HM and control conditions. Our results indicated higher exudation rate for plants challenged with HM. Further, out of 29 organic acids identified and quantified in the root exudates, 8 of them were significantly influenced by HM (e.g., salicylic and terephthalic acid). The transcriptional response of P. putida E36 was significantly affected by the HM addition to the growth medium, increasing the expression of several efflux pumps and stress response-related functional units. The additional supplementation of the growth medium with root exudates from HM-challenged plants resulted in a downregulation of 29% of the functional units upregulated in P. putida E36 as a result of HM addition to the growth medium. Surprisingly, root exudates + HM downregulated the expression of P. putida E36 functional units related to plant colonization (e.g., chemotaxis, motility, biofilm formation) but upregulated its antibiotic and biocide resistance compared to the control treatment without HM. Our findings suggest that HM-induced changes in root exudation pattern may attract beneficial bacteria that are in turn awarded with organic nutrients, helping them cope with HM stress. However, it might affect the ability of these bacteria to colonize plants growing in HM polluted areas. Those findings may offer an insight for future in vivo studies contributing to improvements in phytoremediation measures. [Display omitted] • Heavy metal (HM) treatment of Miscanthus x giganteus increased root exudation. • Salicylic and terephthalic acid concentrations increased in metal-treated plants. • putida E36 responded differently to HM stress in presence or absence of root exudates. • Presence of heavy metals affected P. putida expression of plant colonization traits. [ABSTRACT FROM AUTHOR]

Microbial biofilms are an aggregation of single or multi-species bacteria that acquires the capacity to adhere to any surface where they can act like a wholesome system chemically "speaking with" each other through quorum sensing. This synergism is very prominently noticed in the rhizospheric regions of plant roots subsequently forming a dome which can protect the root-rhizospheric niche from various biotic and abiotic stress. The bacterial EPS have a number of roles like adhesion, cohesion and aggregation of soil particles, retaining water molecules, acts as a potential barrier on the rhizospheric regions, facilitating ionic and genetic information exchange within the matrix component, enhanced production of plant readily available nutrients etc. Keeping this scenario in mind, this study was formulated on to isolate and explore novel rhizobacteria with colossal biofilm forming ability showing great potential as a source of lignocellulolytic plant growth promoting agent. The crop chosen for this study was tea or Camellia sinensis, a quintessential beverage that is consumed across the globe. The rhizospheric region of a woody plant like tea, acts as a hub for lignocellulosic enzyme producing bacteria. The novel rhizobacteria isolated from cultivated tea soil, Bacillus vallismortis TR01K [NCBI Genbank Accession Number MT672714], was found to have an immense biofilm forming potential that ranged approximately 40x times higher than normal standard bacterial biofilm forming potentials when tested under laboratory conditions. Further in vitro characterizations of the novel strain showed it's immense potential to make plant nutrient available, to produce plant growth hormones (IAA, GA3, Cytokinin) and produce plant stress mitigating hormone (ACC deaminase). Lignocellulolytic enzymes are a vital part of lignocellulosic biomass degradation-a sustainable biotechnological approach for enzymes, organic acids, feed and biofuel production. The selected bacteria was tested elaborately for the family of lignocellulolytic enzymes (cellulase, laccase, lignin peroxidase, pectinase, amylase, chitinase, beta glucanase etc.) which showed promising results. Thus, proving the entire set of experiments in compliance with the aforementioned hypothesis that the novel bacterial isolate from tea rhizosphere has a significant biofilm forming potential with a colossal potency for being lignocellulolytic plant growth promoting agent. [ABSTRACT FROM AUTHOR]

Globally, the chemical fertilizers use increases day by day for higher crop yield, which negatively affects the soil ecosystem. Over the past few decades, microbial bio-inoculants (single or multiple strains as consortium) have been recognized as potential plant growth promoters. Multiple microbial strains in a single formulation are a new growing trend for agricultural sustainability. In the present investigation, potential microbial consortium containing mineral solubilizing microbes (MSMs) and nitrogen fixing microbes were sorted out from the rhizospheric region of different crops growing in hilly regions of Himachal Pradesh and efficient bacterial strain were evaluated for growth and physiological parameters of Amaranthus crop. All 180 isolated bacterial strains were screened for phosphorus solubilization using insoluble source of phosphorus (rock phosphate, tricalcium phosphate, and apatite) and nitrogen fixation. The selected phosphorus solubilizers and nitrogen fixers were further screened for other plant growth-promoting attributes like solubilization of K and Zn; siderophores, ammonia, indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid and hydrogen cyanide production. The efficient P-solubilizer and N-fixer bacterial strains were identified on the basis of 16S rRNA gene sequencing as Pseudomanas gessardi EU-LWNA-25 and Erwinia rhapontici EU-B1SP1. These bacterial strains were evaluated for plant growth promotion on Amaranthus crops under natural and controlled conditions. The selected stains increased the growth parameters (shoot/root length and biomass) and physiological (chlorophyll content, total sugar content, phenolics and flavonoids content) parameters of the treated plants compared to untreated control. These efficient MSMs and nitrogen fixing microbes as biofertilizer could be utilized for crops growing in hilly region for agricultural sustainability. • Nitrogen fixing bacteria play a significant role in plant growth promotion and developments. • Microbial consortium of Bacillus sp., Erwinia rhapontici and Pseudomanas gessardi were evaluated for growth of Amaranthus. • Mineral solubilizing bacteria could be used as biofertilizers to establish a sustainable agriculture system. [ABSTRACT FROM AUTHOR]

Jatropha curcas seed cake containing high protein has served as a source of protein hydrolysate applied for plant growth stimulation. Effects of enzymatic and acid protein hydrolysates on the growth of Hua Reau chili were investigated. Toxic compounds, phorbol esters in the seed cake, were removed first. The protein isolate prepared from the phorbol ester-free seed cake was digested by Neutrase, papain, trypsin, pepsin and HCl using various hydrolysis times. Degree of hydrolysis of the protein varied, ranging from 3.8% to 97.3% depending on hydrolysis methods and times. The growth of Hua Reau chili was considerably stimulated by the protein hydrolysate obtained from Neutrase digestion at 2 h and was significantly higher than that of all controls. In addition, the protein hydrolysate of 10 μg/ml obtained from Neutrase digestion at 2 h gave the maximum stem height and diameter of Chinese kale plants. Therefore, the protein hydrolysate of the phorbol ester-free seed cake of J. curcas would be an alternative and novel source of natural plant growth stimulant. [ABSTRACT FROM AUTHOR]

IAA production is among the most important mechanisms used by PGPB to improve plant growth, health, and productivity. Out of twenty-eight telluric bacterial isolates, the four producing high IAA amounts were identified by 16S rDNA gene sequencing as Bacillus subtilis (A7), Bacillus pumilus (E11), and Pseudomonas fluorescens (A5 and E9). IAA production conditions viz. incubation time, pH, temperature, tryptophan concentration, and carbon and nitrogen sources at different concentrations were optimized. These strains showed variations in the optimum of each parameter except incubation time which was 4 days for all strains. Fructose at 0.5% was the optimum carbon source for three of the tested strains. The four strains showed different preferences for the nitrogen source concerning IAA production. • Screening and optimization of IAA production. • Telluric bacteria isolated from northern Algeria. • Utilization of indol acetic acid as phytohormone from Bacillus and Pseudomonas strains. • Main parameters affecting the IAA production from bacteria. [ABSTRACT FROM AUTHOR]

Abstract: Sclerotinia sclerotiorum causes serious yield losses in oilseed rape and other crops worldwide. Field trials were conducted at two locations to evaluate two formulations of oilseed rape seed containing the plant-growth promoting bacterium Bacillus megaterium A6 for suppression of this pathogen. Treatments containing strain A6 in pellet and in wrap formulations resulted in oilseed rape seed yields that were similar to the chemical control and significantly greater than the untreated seed control at both locations. Treatments containing A6 in pellet and wrap formulations also resulted in an incidence of disease caused by S. sclerotiorum that was similar to the chemical control. Both of these treatments significantly decreased disease incidence relative to the untreated seed control and to the respective formulated seed controls (that did not contain strain A6) at both locations. Strain A6 applied to oilseed rape seed in these two formulations promoted growth in greenhouse pot studies conducted with autoclaved soil. In two experiments, these treatments resulted in significant increases in mean shoot dry weight per pot and mean % total N per plant relative to their respective controls containing formulated oilseed rape seed without strain A6 and to the untreated seed control. Both formulations provided stable B. megaterium A6 (≥106 CFU) and seed germination (>85%) over a six month period at room temperature. Experiments reported here indicate the commercial potential of these formulations of B. megaterium A6 for suppression of S. sclerotiorum on oilseed rape. [Copyright &y& Elsevier]

Abstract: In ecosystems, plant and bacterial volatile organic compounds (VOCs) are known to influence plant growth but less is known about the physiological effects of fungal VOCs. We have used Arabidopsis thaliana as a model to test the effects of VOCs from the soil fungus Trichoderma viride. Mature colonies of T. viride cultured on Petri plates were placed in a growth chamber in a shared atmosphere with A. thaliana without direct physical contact. Compared to controls, plants grown in the presence of T. viride volatiles were taller, bigger, flowered earlier, and had more lateral roots. They also had increased total biomass (45 %) and chlorophyll concentration (58 %). GC–MS analysis of T. viride VOCs revealed 51 compounds of which isobutyl alcohol, isopentyl alcohol, and 3-methylbutanal were most abundant. We conclude that VOCs emitted by T. viride have growth promoting effects on A. thaliana in the absence of direct physical contact. [Copyright &y& Elsevier]

Abstract: In the present investigation, we studied resistance imparted by seed treatment with an endophytic strain of Achromobacter xylosoxidans, AUM54, against rice blast caused by Magnaporthe oryzae. In vitro studies showed that A. xylosoxidans AUM54 was able to inhibit mycelial growth of M. oryzae by 11% and was able to increase rice germination and seedling vigor index of rice by 31 and 114%, respectively. AUM54 also showed better survivability in the spermosphere and spermoplane and was able to move systemically through the roots and stem. Among the evaluated carriers, liquid formulation amended with 2% glycerol sustained the maximum bacterial population (7.4 log cfu ml−1) after six-months-storage at room temperature. Plants treated with A. xylosoxidans AUM54 followed by inoculation with M. oryzae showed a significant increase in the activities of defense related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL) and chitinase. A. xylosoxidans AUM54 treatment was able to reduce blast disease incidence by 39% in treated rice plants. Additionally, inoculation with A. xylosoxidans AUM54 significantly enhanced the growth (3–13% plant height), and yield (11–31%) of inoculated rice plants under no-disease and disease conditions in the greenhouse experiments. [Copyright &y& Elsevier]

Abstract: The fungitoxic effects of 66 medicinal plants belonging to different families were evaluated in vitro on Pythium aphanidermatum, the causal agent of chilli damping-off. Of these, Zimmu leaf extract (Allium sativum L. × Allium cepa L.) showed the highest inhibition of mycelial growth of P. aphanidermatum (13.7 mm). The antimicrobial compounds were isolated from Zimmu leaf extract and 22 compounds were identified through gas chromatography mass spectroscopy (GC–MS). Biocontrol agents Trichoderma viride and Pseudomonas fluorescens and Zimmu extract were also tested alone and together in vitro and in vivo experiments for control of P. aphanidermatum. The in vitro studies revealed that combination of T. viride + P. fluorescens + Zimmu leaf extract showed the highest mycelial growth inhibition over the control. Both antagonists were compatible with each other and with Zimmu leaf extract. The pot culture studies revealed that seed treatment with combined application of T. viride + P. fluorescens + Zimmu leaf extract was superior in reducing the pre and post-emergence damping-off incidence (8.3 and 17.0%, respectively), and increased the plant growth and yield (shoot length and root length of 13.7 and 6.3 cm, 146 g/plant, respectively) of chilli when compared to control. [ABSTRACT FROM AUTHOR]

Abstract: Ten strains of Pseudomonas aeruginosa (PN1 ˜ PN10) isolated from rhizosphere of chir-pine were tested for their plant growth promontory properties and antagonistic activities against Macrophomina phaseolina in vitro and in vivo. P. aeruginosa PN1 produced siderophore, IAA, cyanogen and solubilized phosphorus, besides producing chitinase and β-1,3-glucanase. In dual culture, P. aeruginosa PN1 caused 69% colony growth inhibition. However, cell free culture filtrate also posed inhibitory effect but to a lesser extent. After 90 days, P. aeruginosa PN1 increased plant growth and biomass in pots trial containing M. phaseolina-infested soil. PN1 showed the strong chemotaxis toward root exudates resulting in effective root colonization. Moreover, increased population in rhizosphere of these bacteria was also recorded after 90 days of treatment. Thus, chemotactic fluorescent P. aeruginosa PN1 exhibited strong antagonistic property against M. phaseolina, suppressed the disease and improved plant growth of the seedlings of chir-pine proving potential biocontrol agent. [Copyright &y& Elsevier]

The use of bio-fertilizers in agricultural fields in the form of microorganisms is an eco-friendly way of improving crop yield. The applied microbes, however, face challenges while successfully establishing themselves in the rhizosphere or endosphere of plants due to the competing native soil and plant microflora. To this problem, microbial biofilms are a potential solution as they prolong plant-microbe contacts at various plant surfaces often leading to beneficial outcomes. Microbial biofilms are widely studied due to their adverse impacts in the healthcare sector, water distribution system, food industry, and plant diseases. Recent reports suggest that microbial biofilms may have a positive impact on crop productivity. In this article, we have tried to review the various interactions found between plant and their associated microbes leading to co-metabolic associations and discussed the different ways by which microbes communicate in the microenvironments of the biofilm. Metabolically dependent syntrophic biofilms have been discussed as an area to study in the connection with the agricultural system. Syntrophic biofilms, although less known related to plants may influence the plant growth and yield for a better farming system. • In agricultural fields, microbial inoculants often fail to successfully establish themselves. • Multispecies biofilms in plant roots form stable plant associations. • Biofilms are niche for metabolic dependence and syntrophic communication. • Biofilms may play a crucial role in adopting synthetic farming approaches. • Such a microbe-assisted approach may enhance crop productivity and stress tolerance. [ABSTRACT FROM AUTHOR]

Abstract: Two lead (Pb)-resistant endophytic bacteria were isolated from rape roots grown in heavy metal-contaminated soils and characterized. A pot experiment was conducted for investigating the capability of the two isolates to promote the growth and Pb uptake of rape from Pb-amended soil. The two isolates were identified as Pseudomonas fluorescens G10 and Microbacterium sp. G16 based on the 16S rDNA gene sequence analysis. Strains G10 and G16 exhibited different multiple heavy metal and antibiotic resistance characteristics and increased water-soluble Pb in solution and in Pb-added soil. Root elongation assays demonstrated increases in root elongation of inoculated rape seedlings compared to the control plants. Strain G16 produced indole acetic acid, siderophores and 1-aminocyclopropane-1-carboxylate deaminase. Increases in biomass production and total Pb uptake in the bacteria-inoculated plants were obtained compared to the control. The two strains could colonize the root interior and rhizosphere soil of rape after root inoculation. [Copyright &y& Elsevier]

The aim of the study was to characterize halotolerant bacteria and to evaluate their plant growth promotion potential on chia and quinoa seedlings under saline stress. Isolated microorganisms were evaluated for nitrogen fixation, phosphate solubilization, and production of siderophores and indole acetic acid. Three strains and two consortia were selected: Halomonas sp. (SFS), Micrococcus luteus (SA211), Bacillus sp. (HX11), C1 (SA211 + SFS), and C2 (SA211 + HX11). In vitro assays using water agar and half-strength Murashige-Skoog plates showed that an increase in salinity led to an increased seedlings mortality and a decrease in germination (lower than 40%), in total length (varying between 16% and 87% decreases), root length (from 60% to 92% lesser length) and dry weight (from 7% to 86% lower weight). Also, the relative growth index (RGI) decreased for both crops in most treatments, except those with HX11 and C2. These treatments had the highest growth parameters and RGI values in presence of high salinity in chia (50 and 100 mmol/L NaCl) and quinoa (200 and 400 mmol/L NaCl). SA211, the highest producer of indole acetic acid, showed a detrimental effect and anomalous phenotype on plants. Our results suggest that Bacillus sp. HX11, with multiple plant growth promotion traits and tolerance to saline stress, has a great potential as a bioinoculant in saline conditions and could be used as a biofertilizer for crop production. [Display omitted] • Halotolerant bacteria from hypersaline environments had PGP activities. • Bacteria reduced salt toxicity in chia (sensitive) and quinoa (tolerant) seeds. • We propose an index that integrates plant growth parameters. • Bacillus sp. HX11 showed a beneficial growth effect in both crops. • Micrococcus luteus SA211 produced high IAA and showed a detrimental growth effect. [ABSTRACT FROM AUTHOR]

Plants benefit from associations with a diverse community of root-colonizing microbes. Deciphering the mechanisms underpinning these beneficial services are of interest for improving plant productivity. We report a plant-beneficial interaction between Arabidopsis thaliana and the root microbiota under iron deprivation that is dependent on the secretion of plant-derived coumarins. Disrupting this pathway alters the microbiota and impairs plant growth in iron-limiting soil. Furthermore, the microbiota improves iron-limiting plant performance via a mechanism dependent on plant iron import and secretion of the coumarin fraxetin. This beneficial trait is strain specific yet functionally redundant across phylogenetic lineages of the microbiota. Transcriptomic and elemental analyses revealed that this interaction between commensals and coumarins promotes growth by relieving iron starvation. These results show that coumarins improve plant performance by eliciting microbe-assisted iron nutrition. We propose that the bacterial root microbiota, stimulated by secreted coumarins, is an integral mediator of plant adaptation to iron-limiting soils. • Coumarins alter the root microbiota and improve plant growth in iron-limiting soil • The microbiota improves plant iron nutrition via a coumarin-dependent mechanism • The iron-beneficial commensal trait is taxonomically widespread but strain specific • Coumarin-microbiota interaction resolves iron starvation and regulates immune response Iron-limiting soils are widespread, causing significant losses in plant growth and productivity. Harbort et al. show that under iron limitation, plant-secreted coumarin compounds are mediators of a beneficial plant-microbiota interaction. These specialized metabolites alter root microbiota composition and are required for microbiota-mediated plant iron uptake and immune regulation. [ABSTRACT FROM AUTHOR]

Indole-3-acetic acid (IAA) is the most prevalent plant hormone of the auxin family that occurs naturally in the environment and regulates the plant growth and development. The bacteria were isolated from the tomato rhizosphere soils and screened for IAA production. Among the all isolates, the isolate designated as 7MM11 showed maximum amount of IAA (89.22 μg/mL) production in short incubation period (24 h) by HPLC. The isolate was identified as Providencia sp. by its morphological characteristics and 16S rRNA sequence study. Further, optimal conditions such as l -tryptophan concentration, incubation time, agitation, pH, carbon sources, and nitrogen sources, were identified for IAA production. The optimization results suggested that the IAA production increased with medium supplemented with sucrose (0.1%), urea (0.1%), and tryptophan (0.1%) with pH 8.0 at 30 ± 2 °C on a shaker at 150 rpm after 24 h of incubation. The production of IAA by Providencia sp. was further confirmed and characterized with help of thin-layer chromatography and high-performance liquid chromatography. In an in vivo experiment, the tomato seedlings treated with Providencia sp. showed improved germination, seedling vigor index, and enhanced growth promotion compared to un-inoculated control. Thus, the results of this study suggest that Providencia sp. strain 7MM11 is a potent isolate for the maximum production of IAA in short period, which may help in achieving the plant growth promotion. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a serious threat for environment and human health. Rice, the main staple crop is more prone to As uptake. Bioremediation strategies with heavy metal tolerant rhizobacteria are well known. The main objective of the study was to characterize arsenic-resistant yeast strains, capable of mitigating arsenic stress in rice. Three yeast strains identified as Debaryomyces hansenii (NBRI-Sh2.11), Candida tropicalis (NBRI-B3.4) and Candida dubliniensis (NBRI-3.5) were found to have As reductase activity. D. hansenii with higher As tolerance has As expulsion ability as compared to other two strains. Inoculation of D. hansenii showed improved detoxification through scavenging of reactive oxygen species (ROS) by the modulation of SOD and APX activity under As stress condition in rice. Modulation of defense responsive gene (NADPH, GST, GR) along with ars R and metal cation transporter are the probable mechanism of As detoxification as evident with improved membrane (electrolyte leakage) stability. Reduced grain As (~40% reduction) due to interaction with D. hansenii (NBRI-Sh2.11) further validated it's As mitigation property in rice. To the best of our knowledge D. hansenii has been reported for the first time for arsenic stress mitigation in rice with improved growth and nutrient status of the plant. Image 1 • Arsenic tolerant yeast strain (Debaryomyces hansenii) for arsenic stress amelioration in rice plant. • D. hansenii showed arsenate reductase activity. • D. hansenii improved detoxification mechanism in plant. • D. hansenii showed reduced As content in grain. • D. hansenii can be considered as a good potential for lyophilized formulation (like baker's yeast) for As remediation. [ABSTRACT FROM AUTHOR]

Among the extreme habitats, drought is most harsh abiotic stress affecting growth, development and productivity of crops. Plants also face limitations of certain nutrients such as phosphorus required for different physiological and metabolic activities. Stress-adaptive phosphorus-solubilizing microbes in rhizospheric soil can help plants to combat water scarcity and overcome the problem of phosphorus unavailability to plant systems. The present investigation deals with the isolation of drought stress adaptive and P-solubilizing microbes from rhizospheric soil of different cereals and pseudocereals and their role in mitigation of drought stress in great millet. A total of 193 rhizospheric microbes were isolated and screened for their capability to solubilize phosphorus under drought stress. Twenty isolates exhibited P-solubilizing attribute under drought stress, which were further screened for plant growth promoting (PGP) traits such as solubilization of zinc and potassium; production of Fe-chelating compounds, indole acetic acid, hydrogen cyanide and ammonia. On basis of multifunctional PGP traits, two efficient and potential microbes were evaluated for PGP in great millet in vitro under green house with different water regimes. The isolates were found to be efficient in terms of enhancing accumulation of different osmolytes such as glycine betaine, proline, sugars, increased chlorophyll content, and decreasing lipid peroxidation. The isolates were identified by 16S/18S rRNA gene sequencing as Streptomyces laurentii EU-LWT 3 -69 and Penicillium sp. strain EU-DSF-10. To best of our knowledge Streptomyces laurentii has been reported first time as PGP and drought adaptive bacterium. PGP drought-adaptive phosphorus solubilizers could be used as bioinoculants for crops under water scarcity ecosystems. [ABSTRACT FROM AUTHOR]

Biofertilizers consists of the microorganisms bringing about the improvement of the nutrients of the soil enhancing their accessibility to the crops. Plant nutrients form the most vital components of the sustainable agriculture. Producing healthy crops for the fulfillment of the demands of the world's growing population is completely dependent upon kind of the fertilizers being used to provide the plants with all the major nutrients but more dependability on the chemical fertilizers is destroying the environmental ecology and negatively influencing the health of humans. Thus, using microbes as bioinoculants is believed to be the best substitute of chemical fertilizers as eco-friendly manner for plant growth and soil fertility. These microbes are known to be the potent tool to provide substantial benefits to crops for sustainable agriculture. The beneficial microbes colonize the plant (epiphytic, endophytic and rhizospheric) systems of crops and plays significant role in nutrient uptake from surrounding ecosystems of plants. The plant associates microbes have ability to promote growth of plant under the natural as well as extreme conditions. These plant growth promoting microbes enhance the plant growth by various direct and indirect plant growth promoting mechanisms such as biological nitrogen fixation, the production of various plant growth hormones, siderophores, HCN, various hydrolytic enzymes and solubilization of potassium, zinc, and phosphorus. Extensive work on the biofertilizers has been done and even available which clearly reveals that these microbes possess the potential of providing the vital nutrients to the crops in adequate quantities for the enrichment of yield of the crops without disturbing the environment. [ABSTRACT FROM AUTHOR]

The increasing worldwide population is a significant challenge for agricultural food production to feed the alarming rate of the growing world population. The enhancing community directly affected by several factors, including the limitation of agricultural land, environmental damage, and the number of biotic and abiotic stresses, which affect global food production. It is essential to increase agricultural productivity to feed an increasing population. Several approaches are needed, such as greater use of chemicals including fertilizers, pesticides, and herbicides. Several other factors, such as overcome the posture, saline, and drought land, can be improved by using stress-tolerant plant growth-promoting microorganisms. Though, many of the solutions attempted to this problem are not sustainable and are only be valid for the short term. Stresses tolerant plant growth-promoting rhizobacteria (PGPR) can produce bioactive compounds such as gibberellins and indole acetic acid. PGPR also produced several active enzymes under drought, heavy metals, and salts stress. PGPR approach can enhance plant growth and consequently crop yield with maintained eco-friendly environment. The present review focused on the recent advances of PGPR approach in concern to different biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]