Plant microbes Interaction

Background The fundamental role and contributions of phyllosphere habitat in shaping plant functional ecology are poorly investigated, and often underestimated. Phyllosphere -the harsh and dynamic foliar-photosynthetic-habitat is continuously exposed to vagaries of changing weather events during the entire plant life. With its adapted microbiota, the phyllosphere-niche brings microbial diversity to the plant-holobiont pool and potentially modulates a multitude of plant and agronomic traits. The phyllomicrobiome structure and the consequent ecological functions are vulnerable to a host of biotic (Genotypes) and abiotic-factors (Environment) which is further compounded by agronomic-transactions on domesticated agricultural crops. However, the ecological forces driving the phyllomicrobiome assemblage and functions are among the most under-studied aspects of plant biology. Despite the reports on the occurrence of diverse prokaryotic phyla such as Proteobacteria, Firmicutes, Bacteroides,...

Objective: Study the diversity of cultivable rhizospheric bacteria associated to Agave americana, and select native strains with potential as plant growth-promoting bacteria (PGPB). Design/methodology/approach: The isolated bacteria were phenotypically characterized. The genetic diversity and identity of the strains were revealed by genomic fingerprints and by sequencing of 16S rRNA gene. Plant growth promoting ability and plant inoculation assays were evaluated to know the potential as PGPB. Results: A total of 235 strains were isolated from A. americana rhizosphere and were classified within of 10 different bacterial genera. Rhizobium, Pseudomonas, Acinetobacter had high potential as PGPB. Study limitations/implications Cultivable approach was used to study rhizobacteria. A metagenomic study could expand the knowledge about the structure and diversity of bacterial community associated to A. americana. Findings/conclusions Rhizosphere bacteria have potential use as biofertilizer fo...

Potassium (K) is the foremost macronutrients for growth of plant, soil health and fertility. The huge application of NPK chemical fertilizers negatively impacts the economy and is a threat to environmental sustainability. The rapid depletion of K mineral in soil is due to the application of agrochemicals agricultural fields for the production of crops in India. In present investigation, K-solubilizing microbes (KSM) were isolated and enumerated from cereal crops growing in Sirmour Himachal Pradesh. A total 125 bacteria were isolated and screened for K-solubilization on Aleksandrov agar plates and found that 31 bacterial strains exhibited K-solubilization. These 31 K-solubilizing strains of bacteria were additionally screened for other plant growth promoting (PGP) potential including solubilization of minerals, production of siderophores, ammonia, hydrogen cyanide and indole acetic acids. The performance of an efficient K-solubilizer was evaluated for plant growth promoting ability in pot assay under in vitro conditions. The strain EU-LWNA-25 positively influenced shoot length, fresh weight, carotenoids and total sugar content than the full dose, half dose and control. The strain enhancing physiological and growth parameters was identified by BLASTn analysis as Pseudomonas gessardii EU-LWNA-25. K-solubilizing plant growth promoting bacteria could be suitable bioinoculants for Rabi seasonal crops and overcomes the challenges of sustainable agriculture in K-deficient soil.

Agriculture faces challenges to fulfil the rising food demand due to shortage of arable land and various environmental stressors. Traditional farming technologies help in fulfilling food demand but they are harmful to humans and environmental sustainability. The food production along with agro-environmental sustainability could be achieved by encouraging farmers to use agro-environmental sustainable products such as biofertilizers and biopesticides consisting of live microbes or plant extract instead of chemical-based inputs. The eco-friendly formulations play a significant role in plant growth promotion, crop yield and repairing degraded soil texture and fertility sustainably. Mineral solubilizing microbes that provide vital nutrients like phosphorus, potassium, zinc and selenium are essential for plant growth and development and could be developed as biofertilizers. These microbes could be plant associated (rhizospheric, endophytic and phyllospheric) or inhabit the bulk soil and d...

Erwinia is a genus of Enterobacteriacea containing mostly pathogens, which cause soft rot disease in many ornamental plants and crops, including Asparagus officinalis. Chemical treatments to control Erwinia have lost their attractiveness because of the development of resistant strains and the negative impacts on the environment and human health. Therefore, the study of biological controls of soft rot disease has gained great importance. There are several types of microorganisms that show activity against Erwinia spp. such as Pseudomonas fluorescence, Bacillus subtilis, and Streptomyces spp. Among them, Streptomyces spp. are found to be the most effective control agents. In this study, 64 isolates of Streptomyces were screened for their antibacterial activity against Erwinia spp. The results indicated that 18 isolates showed an antagonistic reaction against Erwinia spp. Among them, isolate D5.1 showed the highest inhibition activity. In addition, the morphological and antibacterial a...

Phosphate-solubilizing fungus (PSF) makes phosphorus in soils far more available to plants. The goal of this study was to look at a number of soil fungus to see which ones help plants develop better. The focus was on their ability to break down phosphates, make siderophores, and make indole-3-acetic acid (IAA). We used rDNA sequencing of the ITS regions to figure out what kind of fungi they were, and then we tested how well they could make things grow in a lab setting. Aspergillus sydowii, Aspergillus terreus, and Penicillium capsulatum all dissolved phosphates at varying rates. A. terreus dissolved the most tricalcium phosphate (TCP). A. terreus produced the most IAA (17.82 µg/ml), followed by P. capsulatum and A. sydowii. Also, A. terreus produced the most siderophores, which suggests that it may help plants take in more iron. We tested Vigna mungo, Sorghum bicolor, and Glycine max in pots. We employed eleven treatments and three copies of soil that had been sterilized and dirt that had not been sterilized. The plants that got the biofertilizer grew a lot taller, had longer roots, and weighed a lot more when they were wet. It is important to correctly identify species and screen for PSF so that researchers can have a clearer idea of the taxonomic picture when choosing suitable taxa for future plant growth-promoting applications. These results show that these fungal strains, whether employed alone or in combination, have important traits that help plants grow and might be exploited as bioinoculants in sustainable farming.

Solid waste management has become a global issue owing to various environmental, social and health problems associated with its disposal. The two capital cities of the state, Srinagar and Jammu, generate 770 tonnes of solid waste daily and in absence of proper scientific disposal methods, this waste is emerging as major source of air, water and soil pollution. Stringent efforts are required to find methods and means for disposal of these wastes. Although there are a vast array of methods for disposal but, the microorganisms that require low temperatures for conversion of solid wastes into manure particularly in the temperate regions shall go a long way to find round the year solution for this problem. Since Kashmir valley has cold temperatures during most parts of the year, for that purpose we tried to combine cold tolerant microorganisms and earthworms for solid waste decomposition with a view to enhance nutrient status of the manure. During our research program, a total of twenty ...

Sheep grazing induces the reduction of perennial grass cover and the increase of shrub cover with high concentration of chemical defences. We analysed the effects of secondary metabolites released from green and senesced leaves of the shrub Larrea divaricata on soil microbial activity and the establishment of perennial grasses in arid ecosystems of the Patagonian Monte. We carried out microcosm experiments with soil from plant patches without and with L. divaricata and inert substrate seeded with the perennial grasses Poa ligularis and Nassella tenuis, which are characteristic of the Patagonian Monte. Microcosms were subjected to three watering treatments: distilled water and aqueous extracts of green and senesced leaves of L. divaricata with high concentration of soluble phenolics. We assessed the microbial N-flush and net-N mineralization in soil, and seed germination, survival, and biomass of both perennial grass species. Aqueous leaf extracts led to a 29% increase in microbial N-flush and a 20% reduction in the net-N mineralization. Seed germination was less negatively affected by aqueous leaf extracts in P. ligularis ( \ 18% reduction) than in N. tenuis (2-69% reduction). Survival of P. ligularis was not affected by aqueous leaf extracts while that of N. tenuis was 21-45% reduced only in the soil from plant patches without L. divaricata. Biomass accumulation of both perennial grass species was negatively affected by aqueous extracts of senesced leaves. We concluded that soluble metabolites extracted from L. divaricata may have positive or negative effects on microbial activity and potential allelopathic effects on perennial grass regeneration depending on species.

The aim of this study was to test the hypothesis that composts and fungicide application on suckers could control root rot disease of cocoyam, a major disease constraint of the production of this crop in Cameroon. Experiment was conducted in a screen house through a complete randomized design with five replicates. Eight compost types made from four different abundant and locally available weed species (Gramineae family) mixed either with poultry or pig manure were prepared. Mature compost was inoculated 48 hours before planting to enable compost-pathogen interaction. Plant growth parameters were highest in compost made from Tithonia diversifolia compare to others compost types. Disease incidence and severity was significantly (P≤0.05) reduced in all compost amended pots than in control at 12 weeks after inoculation. The most suppressive compost was compost made from T. diversifolia followed by Chromolaena odorata both associated with poultry manure. These compost types registered th...

Since food is a man’s foremost biological need, feeding the ever-growing world’s populations organically without recourse to agrochemicals becomes a major challenge facing scientists globally. Decades ago, conventional agriculture substantially contributed to the decrease in plant and biodiversity in Agro-ecosystems. Conversely, organic farming is wholesome, environmentally friendly, permitting interactions of soil minerals, organic matter, microorganisms, insects, plants, animals, and humans to create coherent and stable Agro-ecosystems with many benefits and a pollution-free environment. Several different methods of organic farming systems are discussed here for their contributions to the preservation, promotion of biodiversity and plant fitness within agricultural fields. The present review appraises the contributions of some of these approaches, their impacts on soil structure, fertility, plant health and productivity.

The aim of the present study was to isolate phosphate solubilizing bacteria from wheat rhizosphere and investigate their potential for plant growth promotion. Three phosphate solubilizing bacterial strains were isolated by serial dilution method from the rhizosphere of wheat grown under wheat-cotton and wheat-rice crop rotation. 16S rRNA gene sequence of the isolates WS-1, T-34 and T-41 showed 98% similarity to those of Azospirillum, Bacillus and Enterobacter sequences in NCBI data base, respectively. The bacterial strain WS-1 clustered with Azospirillum brasilense strains in the phylogenetic tree constructed using NCBI data base sequences of the genus Azospirillum. The bacterial isolate T-34 formed cluster with Bacillus licheniformis strains in the phylogenetic tree constructed using 16S rRNA sequences of the genera Bacillus and Paenibacillus. In the phylogenetic tree constructed using 16S rRNA gene sequences of genus Enterobacter, the isolate T-41 clustered with Enterobacter amnigenus strains. Phosphate solubilizing activity of the bacterial strains in Pikovskaya medium was investigated by molybdate blue color method using spectrophotometer while organic acids produced in the medium were detected on HPLC. In a growth medium containing insoluble tri-calcium phosphate and supplemented with sucrose, maltose, glucose or galactose as single C-source, all the three isolates produced organic acids like acetic acid, citric acid and gluconic acid for phosphate solubilization. Among the organic acids detected, acetic acid was produced in highest amounts by all strains tested in the media containing different sugars. Maximum acetic acid (56.7 µg/ml) was produced by Bacillus strain T-34 in medium supplemented with sucrose and citric acid (36.2 µg/ml) by the same strain on glucose supplemented medium. Oxalic acid was produced by Bacillus strain T-34 (2.89 µg/ml) and Enterobacter strain T-41 (5.93 µg/ml) only in the medium containing galactose as C-source. Maximum amount of gluconic acid (25.4 µg/ml) was produced by Azospirillum strain WS-1 in the medium containing glucose as C-source. Highest P solubilization activity (298.3 µg/ml) was observed in Bacillus strain T-34 grown on sucrose supplemented medium. Maximum P solubilization was detected in Enterobacter strain T-41 (292.2 µg/ml) in medium containing maltose. Azospirillum strain WS-1 showed maximum P solubilization (218.1 µg/ml) in medium containing glucose as single C-source. All the three bacterial strains produced growth hormone IAA in the growth medium supplemented with tryptophan. Quantification on HPLC indicated maximum IAA production (31.15 µg/ml) by Bacillus strain T-34. A pot experiment conducted to study the effect of bacterial isolates on growth of wheat showed that inoculation with Azospirillum, Bacillus and Enterobacter strains increased the grain yield of wheat by 9.3%, 14.8%, 13.1%, respectively over non-inoculated control. Under field conditions, increase in grain yield of plants inoculated with Azospirillum, Bacillus and Enterobacter was 11.2%, 15.7% and 5.6%, respectively compared with non-inoculated plants.These results indicated that bacterial isolates having plantbeneficial traits like phosphate solubilization and IAA production and capable of improving growth of wheat when used as inoculants qualify for production of biofertilizer for wheat crop.

The identification and classification of microbial flora in bodies of fresh water has the potential of enhancing our understanding of this ecosystem and improving water management and bioremediation. This effort may be facilitated by the use of remote sensing technologies. For the last 3 years our undergraduate students have collected water samples in the Lake Ontario Rochester Embayment and Irondequoit Bay with the goal of constructing a database of bacterial species and water parameters (e.g. organic matter and chlorophyl content). Such a database is necessary to establish potential correlations between the presence of certain bacterial species and water parameters that can be measured using satellite imagery collected by the Landsat 8 OLI and TIRS sensors. In the past we reported initial efforts at mapping the distribution of bacterial species using 16S rRNA. Here we present our results for the summer of 2015 and present a compounded analysis of 3 consecutive summers. Of approxim...

Soil bacteria have important roles in biogeochemical cycle for soil fertility and have been manipulated for ecologically-friendly crop production.  The search for beneficial association between microbes and plants for promoting growth and health should be studied for tomato growth improvement. The study aimed to  evaluate 19 microbial isolates which produced indole acetic acid (IAA) affecting growth and development of tomato (Palupi variety), and  molecularly identify the most effective isolates in improving tomato growth based on 16s rDNA sequences. The experiment was conducted in pots using a complete randomized design with three replications. The parameters observed included plant height, plant dry weight, root length, root dry weight, and fruit fresh weight.  The isolates that significantly improved tomato growth were molecularly identified using 16s rRNA sequence. The phenotypic properties such as IAA content and phosphate solubilizing index (PI) of the superior isolates were d...

Multifunctional microorganisms can contribute significantly to improve plant performance and are innovative technology for sustainable development. Thus, objective of this study was to determine the effect of bioagents applied alone or in mix on the performance of upland rice. The experiment was conducted in a greenhouse in a completely randomized design with four replications. The 26 treatments consisted of the rhizobacteria Bacillus sp. (BRM 32109, BRM 32110 and 1301), Azospirillum sp. ( ), Azospirillum brasilense (Ab-V5), Pseudomonas sp. (BRM 32112), Pseudomonas fluorescens (BRM 32111), Burkholderia pyrrocinia (BRM 32113), Serratia sp. (BRM 32114), and a fungal genus formed by a pool of Trichoderma asperellum (T-06, T-09, T-12, and T-52), applied alone or in mix, plus a control treatment without microorganism application. The most effective treatments were the mixes of microorganisms 1301 + Ab-V5 and BRM 32114 + pool of Trichoderma asperellum, as they provided an average increase of 123 and 88% in the number of panicles and 206 and 167% in the grain yield of upland rice plants, respectively. Mixes of 1301

Research objective: The main objective of this article is to report the results obtained from the use of new microbial strains on vegetable plants. In particular, the article will deal with two important topics: i) the study of the effect of microorganisms on the biomass of vegetable plants; ii) the possible control of mortality due to diseases such as powdery mildew and Cladosporiosis. The information reported in this research work can support the design of cropping systems in which agricultural sustainability is fundamental due to the presence of microorganisms with biostimulating activity and as a possible alternative to synthetic plant protection products.

Plant-plant chemical interactions in forests can have a strong impact on the biodiversity and dynamics of these ecosystems, particularly in Mediterranean forests where plants exhibit a high secondary metabolite diversity. Allelopathic interactions in Mediterranean ecosystems have been mostly studied in the first stages of ecosystem dynamics, shrublands and pine forests, but little is known about these interactions in mature oak forests. In this study, the allelopathic effect of three main woody species of downy oak forests (Quercus pubescens, Acer monspessulanum and Cotinus coggygria) on germination and growth of two herbaceous species (Festuca ovina and Linum perenne) was tested through aqueous extracts obtained from different leaf phenological stages (green, senescent and litter). The germination velocity of the two target species was inhibited by the aqueous extracts of senescent leaves from all the woody species. The growth of F. ovina seedlings was affected by aqueous extracts of green leaves of all the woody species, while the growth of L. perenne was only affected by aqueous extracts of green leaves of A. monspessulanum. This shows that (i) allelochemicals released by leaf leachates of the dominant woody species could control the dynamic of the herbaceous species, and then their potential competition with trees and (ii) allelopathic effects of woody species are related to their phenological stage and seem consistent with the development stage of target species.

aerogenes), STMPSB 4 (Enterobacter aerogenes) and STMPSB 8 (Klebsiella pneumonia) were regarded as good gluconic acid producing bacteria. A strong correlation of 0.795, significant at the level of 0.01 was observed between gluconic acid concentration and calcium phosphate solubilisation. The detection of pyrroloquinoline quinone (pqq C) gene in eight of the bacterial isolates indicates that direct oxidation pathway was used during the biosynthesis of gluconic acid with the aid of pyrroloquinoline quinone cofactor.

The symbiotic properties of rhizobial bacteria are driven by the horizontal gene transfer of symbiotic genes, which are located in symbiosis islands or on plasmids. The symbiotic megaplasmid pDOA9 of Bradyrhizobium sp. DOA9, carrying the nod, nif, fix, and type three secretion system (T3SS) genes, has been conjugatively transferred to different Bradyrhizobium strains. In the present study, non-nodulating B. cosmicum S23321, which shows a close phylogenetic relationship with Bradyrhizobium sp. DOA9, but lacks symbiotic properties, was used to carry pDOA9 (annotated as chimeric S2:pDOA9). The results obtained showed that pDOA9 conferred symbiotic properties on S23321; however, nodulation phenotypes varied among the DOA9, chimeric ORS278:pDOA9, and S2:pDOA9 strains even though they all carried symbiotic pDOA9 plasmid. S23321 appeared to gain symbiotic nodulation from pDOA9 by processing nodulation genes and broadening the host range. The present results also showed the successful formation of active nodules in Arachis hypogaea (Dalbergoid) and Vigna radiata (Millitoid) by chimeric S2:pDOA9, while Crotalaria juncea (Genistoid) and Macroptilium atropurpureum (Millitoid) formed nodule-like structures. The formation of nodules and nodule-like structures occurred in a nod factor-dependent manner because the nod factor-lacking strain (S2:pDOA9ΩnodB) completely abolished nodulation in all legumes tested. Moreover, T3SS carried by S2:pDOA9 exerted negative effects on symbiosis with Crotalaria juncea, which was consistent with the results obtained on DOA9. T3SS exhibited symbiotic compatibility with V. radiata when nodulated by S23321. These outcomes implied that pDOA9 underwent changes during legume evolution that broadened host specificity and the compatibility of nodulation in a manner that was dependent on the chromosomal background of the recipient as well as legume host restrictions.

the genus Streptomyces recovered from rhizospheric soil of Triticum vulgaris, Zea mays and Vicia faba cultivated in Assuit and New Valley Governorates of Egypt, ten isolates were capable of producing high amounts of L-glutaminase enzyme. The most potent L-glutaminase producer isolate was Streptomyces sp. ASU319 recovered from rhizosphere of Triticum vulgaris. The higher producer actinomycete isolate was identified by sequencing of 16S rRNA as Streptomyces variabilis ASU319 and was deposited in the GenBank nucleotide sequence database under accession number KC145278. Factors affecting L-glutaminase production by the Streptomyces variabilis ASU319(KC145278) were examined and the results revealed that the maximum L-glutaminase value was obtained when the isolate cultivated in the production broth medium supplemented by glutamine 8 mg/ml, adjusted at pH 4 and incubated at 35 °C. These results suggest that L-glutaminase-producing Streptomyces variabilis ASU319 could be used as a plant gr...

Control c.f Neoleucinodes ele'ai,ialis (Guenée) (Lepidoptera: Pyralidae) with Physiological Insccticidcs in Staked l'oniato Plants AESTRACT-Two le1cl trials were conducted from 1989 lo 1990, lo evaluate ihc efficiencv of physio!ogical insecticides ou lhe toniato fruii horcr. Neoleueinodes elegantulis (Guenée). Products and rates/1 00 1 of water were: chloriluazuron 50 CE (50: 75 and 100 ml): trifluniuron 250 PM (100 and 200 g); abamectin 18 CE (100 and 200 ml); abarnectin 1$ CE + Bacilius t/ur,ingiensis (100 ml + 200 g and 200 ml + 200 g) and permethrin 500 CE (20 ml). The efficacy of the reatments was evaluatcd aI harvest by counting damaged fruits, and horer presence in 10maIo fruits. The decreasing order of cfliciency was: abamectin > permethrin > tuilumuron > chioriluazuron. The former three showed more ilian 80% of efficiency.

Control c.f Neoleucinodes ele'ai,ialis (Guenée) (Lepidoptera: Pyralidae) with Physiological Insccticidcs in Staked l'oniato Plants AESTRACT-Two le1cl trials were conducted from 1989 lo 1990, lo evaluate ihc efficiencv of physio!ogical insecticides ou lhe toniato fruii horcr. Neoleueinodes elegantulis (Guenée). Products and rates/1 00 1 of water were: chloriluazuron 50 CE (50: 75 and 100 ml): trifluniuron 250 PM (100 and 200 g); abamectin 18 CE (100 and 200 ml); abarnectin 1$ CE + Bacilius t/ur,ingiensis (100 ml + 200 g and 200 ml + 200 g) and permethrin 500 CE (20 ml). The efficacy of the reatments was evaluatcd aI harvest by counting damaged fruits, and horer presence in 10maIo fruits. The decreasing order of cfliciency was: abamectin > permethrin > tuilumuron > chioriluazuron. The former three showed more ilian 80% of efficiency.

Natural sources, particularly microbes yield active molecules that have wide application in food and pharmaceutical industries, degradation of hazardous bacterial biofilms, etc. Safety and acceptability of such drugs attract researchers’ attention for new drug discovery. Here, we explored biologically active microbial strains having therapeutic applications isolated from five different geographical areas of India. On screening, we found 10 strains capable of producing chitinase (Chi), seven cholesterol oxidase (COD), five glutaminase (Gln) and two heparinase (Hep) producing strains. Most of the isolated strains were found to be actinomycetes. Morphological and biochemical characterization of the strains suggest that the selected 13 isolates belong to the genus Streptomyces. Out of which, four were characterized through 16S ribosomal RNA gene analysis as Streptomyces xanthochromogenes MTCC 11937 (S1), Streptomyces violascens (N1), Streptomyces xanthopheus MTCC 11938 (H1) and Streptom...

Modern agriculture practices heavily depend on the application of chemical fertilizers and continuous application disturbs the soil quality and health. Fluorescent Pseudomonas are the well characterized group of bacteria proficient in plant growth promotion and have excellent phosphate solubilizing abilities and solubilize insoluble phosphate to plants available form via secretion of organic acids. This study focused on the phosphate solubilization ability of Pseudomonas, arouse of Aloin-A molecule, gluconic acid production, as well as biometric parameters of key medicinal plant, the Aloe vera (Aloe barbadensis). Two strains (P. putida and Pseudomonas sp.) were found very effective PSBs and solubilized 236.73 and 153.73 mg L −1 phosphate, respectively. High-performance liquid chromatography analysis (HPLC) showed the production of gluconic acid (GA). P. putida and P. sp. produced 23970 ± 231 and 21538 ± 129 mg L −1 GA, respectively. Inoculation of the plants with consortium of P. putida and Pseudomonas sp. enhanced the plant growth, soil available P and phosphate uptake in plants than individual inoculation. An increase in aloin-A content (18.15 and 28.71 fold) was recorded in A. barbadensis treated with a PSB consortium in a soil amended without and with TCP (tricalcium phosphate), respectively. P-uptake ultimately enhances the aloin-A synthesis and biomass of plant. Therefore, agronomic attributes of Aloe vera plants can be improved for used as a medicinal plant through application of potent Fluorescent Pseudomonas.

In this study, 18 plant growth-promoting bacterial (PGPB) strains were isolated from the rhizosphere of both Red silk-cotton tree (Bombax malabaricum) and Chinese banyan (Ficus retusa). Culture morphology was observed and genotypic characterization was accomplished by sequencing partial 16S rRNA gene. Plant growth promotion traits and antagonistic activities of the strains against phytopathogenic fungi were evaluated. Among all strains, Bacillus thuringiensis (MN419208) exert the highest indole acetic acid (38 µg/ml), produced exopolysaccharides (587.2 µg/ml), and fixed nitrogen which in turn increased both fresh and dry weights of bean plants by 41.5% and 18.8%, respectively. In another greenhouse experiment studying the antifungal activities of seven strains and their co-culture against Rhizoctonia solani (LN735538), B. sonorensis MN419205, B. wiedmannii MN419207, B. subtilis MN419218, and the mixture of (MN419207) and (MN419208) reduced total damping off from 81.7% in control to 30%, 35%, 35%, and 38.3%, respectively, and reduced disease severity index from 33.3% to 20.5%, 22.5%, 14.2%, and 19.3% as well. Our data indicate that these strains are effective in promoting plant growth and in inhibiting R. solani infection nonetheless field experiments are needed to examine their effectiveness as a viable alternative to chemical fertilizers and conventional pesticides.

The occurrence of phosphate-solubilizing fungi in coconut plantation soil types was investigated. The laterite, alluvial and clayey soils harboured more of the P-solubilizing fungi than the sandy soils. The isolated P-solubilizing fungi solubilized 26 to 74 per cent of the tricalcium phosphate in 5 to 15 days. The competitive saprophytic ability of the active P-solubilizing fungi in soil varied between the isolates. Eight fungi with high P-solubilizing capacity and high competitive saprophytic ability were recognised. They have better capacity to survive in soil and express their role in P-solubilization.

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International audienceThe interest for plant interactions, especially between crop and weed species, in agricultural situations has increased with the pressure to reduce the use of chemical inputs. Thus, a better knowledge is required in plant traits mediating the issue of plant competition and how this competition is impacted by the environment. Nitrophily is a plant trait referring to plant habitat, ranging from oligotrophic species mostly found in soils with low N content to nitrophilic species better adapted to soils with high N content. We hypothesize that nitrophily impacts (i) the issue of plant-plant interactions, through competition for N and light and (ii) plant associations-rhizospheric microbial community interactions. We can expect that microbial community from nitrophilic/oligotrophic roots association is (i) different from community associated to the same plants cultivated alone, and (ii) differently impacted according to the association type. To test these hypotheses...

The use of leaf roll discs for in vitro propagation and genetic transformation of sugarcane was investigated. For in vitro propagation, three varieties namely, M 3035/66, S 17 and R 570 were used, and the number of shoots produced from leaf roll discs was compared to that of apical buds. No shoots were regenerated from apical buds of variety S 17 following a culture period of 24 weeks, as they were all either contaminated or oxidized. With M 3035/66 and R 570, only few shoots were obtained. On the other hand, using leaf roll discs, contamination and oxidation were minimal resulting in more than 70% of the cultured explants forming shoots. Prolific shoot regeneration occurred in all three varieties with a total of 400 and 280 shoot clumps produced in varieties M 3035/66 and S 17 respectively, and 250 clumps in R 570. For genetic transformation, leaf roll discs of varieties M 292/70 and M 3035/66, pre-cultured for 10 days on callus induction medium, were bombarded with plasmid pAHC25 containing the gus and bar genes using the Bio-Rad PDS-1000/He Particle Delivery System. After selection on bialaphos, 66 and 24 plants of M 3035/66 and M 292/70 were respectively regenerated and transferred to the glasshouse. Fifty-eight well-established plants of M 3035/66 and 17 of M 292/70 were sprayed with 0.1% herbicide Basta ® four weeks later. Two plants of the latter variety were highly resistant to the herbicide whilst one displayed moderate tolerance. Upon analysis by PCR, all three plants were found to contain the bar gene. For M 3035/66, seven plants with a functional bar gene were obtained. Gene integration was confirmed by Southern blot analysis.

Based on soil depth and nutritional requirements, fungi are the basic components of soil microbes that usually make up more of the soil biomass than bacteria. Phosphate solubilizing fungi were isolated from the soil of the Marathwada district of Maharashtra in the current study and all fungal isolates were tested for their capacity to solubilize phosphate. Total 40 isolate were isolated and only 11 fungal isolates were showed P-solubilizing ability. Among these Aspergillus niger (PQ9), Trichoderma spp (PQ36), Penicillium spp (PQ19) fungal isolates showed significant zone of solubilization with 34, 31 to 30 mm selective agar medium after 48 hours of incubation. The potent phosphate solubilizing fungi were identified 18S rRNA analysis. The study therefore proposed that these fungal species have strong phosphate solubilizing properties and can be used for excellent crop productivity as a biofertilizer.

Endophytic actinobacteria aid in plant development and disease resistance by boosting nutrient uptake or producing secondary metabolites. For the first time, we investigated the culturable endophytic actinobacteria associated with ten epiphytic orchid species of Assam, India. 51 morphologically distinct actinobacteria were recovered from surface sterilized roots and leaves of orchids and characterized based on different PGP and antifungal traits. According to the 16S rRNA gene sequence, these isolates were divided into six families and eight genera, where Streptomyces was most abundant (n=29, 56.86%), followed by Actinomadura, Nocardia, Nocardiopsis, Nocardioides, Pseudonocardia, Microbacterium, and Mycolicibacterium. Regarding PGP characteristics, 25 (49.01%) isolates demonstrated phosphate solubilization in the range of 61.1±4.4 - 289.7±11.9 µg/ml, whereas 27 (52.94%) isolates biosynthesized IAA in the range of 4.0 ± 0.08 - 43.8 ± 0.2 µg/ml, and 35 (68.62%) isolates generated ammo...

This study aimed to isolate and identify phosphate solubilizing microorganisms from rhizosphere soils and evaluate their plant growth-promoting traits in vitro. Fifty-six potential phosphate-solubilizing bacteria were isolated, and ten isolates were selected for further characterization based on their performance. Burkholderia species were found to be the predominant solubilizers of insoluble phosphorus sources. Two strains, B. vietnamiensis-OP984178 and B. ambifaria-OP984173, showed the ability to release soluble phosphorus from different sources, including tricalcium phosphate, ferric phosphate, and hard Minjingu rock phosphate powder. Both isolates also demonstrated production of indole acetic acid, with B. vietnamiensis-OP984178 and B. ambifaria-OP984173 producing up to 23.45 µg/ml and 24.24 µg/ ml, respectively. Furthermore, the strains showed antifungal efficiencies of 31.48% and 24.81%, respectively, when co-inoculated with Fusarium proliferatum-MZ497514 on potato dextrose agar. The study also identified the nitrogen fixation potential of the two strains. Overall, the findings highlight the potential of the selected Burkholderia strains as biofertilizers and biocontrol agents, making them valuable candidates for sustainable agriculture practices. Further research is recommended to explore the potential of these strains using test crops.

The isolation and identification of beneficial bacteria from the active phase of composting is considered to be a key bio-quality parameter for the assessment of the process. The aim of this work was the selection and identification of beneficial bacteria from a co-composting experiment of vegetable waste (VW), olive oil mill waste (O 2 MW), and phosphate sludge (PS). Phosphate-solubilizing strains were isolated from the thermophilic phase using Pikovskaya (PVK) solid medium supplemented with tricalcium phosphate Ca3 (PO4) (TCP) as the sole source of phosphorus (P). Therefore, the selected isolate Alcaligenes aquatilis GTE53 was tested to tolerate abiotic stresses (different levels of temperature, variable pH, high salinity and water stress). The isolate was also assessed for indole acetic acid (IAA) and siderophores synthesis, nitrogen fixation, phenol degradation and pathogens inactivation. The quality of the co-composting process was also investigated by monitoring the physico-chemical parameters. The obtained results showed that A. aquatilis GTE53 displayed a higher solubilization index of 2.4 and was efficiently dissolved, up to 162.8 and 247.4 mgÁmL À1 of inorganic phosphate from PS and phosphate rock (PR), respectively. A. aquatilis GTE53 exhibited siderophores and IAA release, along with atmospheric nitrogen fixation. In addition to that, A. aquatilis GTE53 showed a high resistance to heat and tolerance to acidic and alkaline pH, high salinity and water stress. Moreover, A. aquatilis GTE53 could degrade 99.2% of phenol from a highconcentrated medium (1100 mgÁL À1 of phenol) and can inactivate the most abundant pathogens in industrial wastes: Escherichia coli, Streptococcus sp., Salmonella sp., and Fusarium oxysporum albedinis. Analysis of temperature, pH, electrical conductivity, carbon/nitrogen (C/N) ratio, indicated successful cocomposting. An efficient transformation of P to the available form and a great abatement of polyphenols, were also recorded during the process. The findings of this study will help to advance the understanding of A. aquatilis GTE53 functions and will facilitate its application to promote beneficial microbial organisms during composting, thus obtaining a high-quality product.

Root exudates are thought to play an important role in plant-microbial interactions. In return for nutrition, soil bacteria can increase the bioavailability of soil nutrients. However, root exudates typically decrease in situations such as drought, calling into question the efficacy of solvation and bacteria-dependent mineral uptake in such stress. Here, we tested the hypothesis of exudate-driven microbial priming on Cupressus saplings grown in forest soil in custom-made rhizotron boxes. A 1-month imposed drought and concomitant inoculations with a mix of Bacillus subtilis and Pseudomonas stutzeri, bacteria species isolated from the forest soil, were applied using factorial design. Direct bacteria counts and visualization by confocal microscopy showed that both bacteria associated with Cupressus roots. Interestingly, root exudation rates increased 2.3-fold with bacteria under drought, as well as irrigation. Forty-four metabolites in exudates were significantly different in concentration between irrigated and drought trees, including phenolic acid compounds and quinate. When adding these metabolites as carbon and nitrogen sources to bacterial cultures of both bacterial species, eight of nine metabolites stimulated bacterial growth. Importantly, soil phosphorous bioavailability was maintained only in inoculated trees, mitigating drought-induced decrease in leaf phosphorus and iron. Our observations of increased root exudation rate when drought and inoculation regimes were combined support the idea of root recruitment of beneficial bacteria, especially under water stress. Editor's evaluation This paper will be of interest to those interested in plant-microbe interactions under drought. Trees can exchange root exudates for minerals with soil bacteria. In a pot experiment under realistic conditions, the authors indicate that this exchange persists, and may be protective, when plants experience drought stress. The combination of methods used is an important strength: visualizing bacterial colonization of roots, measuring root exudation and mineral uptake, in conjunction with separate assays of bacterial growth responses to chemicals released by trees.

Certain rhizobacteria can be applied to remove arsenic in the environment through bioremediation or phytoremediation. This study determines the minimum inhibitory concentration (MIC) of arsenic on identified rhizobacteria that were isolated from the roots of Ludwigia octovalvis (Jacq.) Raven. The arsenic biosorption capability of the was also analyzed. Among the 10 isolated rhizobacteria, five were Gram-positive (Arthrobacter globiformis, Bacillus megaterium, Bacillus cereus, Bacillus pumilus, and Staphylococcus lentus), and five were Gram-negative (Enterobacter asburiae, Sphingomonas paucimobilis, Pantoea spp., Rhizobium rhizogenes, and Rhizobium radiobacter). R. radiobacter showed the highest MIC of >1,500 mg/L of arsenic. All the rhizobacteria were capable of absorbing arsenic, and S. paucimobilis showed the highest arsenic biosorption capability (146.4 ± 23.4 mg/g dry cell weight). Kinetic rate analysis showed that B. cereus followed the pore diffusion model (R2 = 0.86), E. a...

Fungal endophytes are microfungi that live in plants without causing apparent symptoms of infection. The purpose of this work was to identify the endophytic fungi isolated from the medicinal plant Carpobrotus edulis collected in the Atlantic coast region of Rabat city in Morocco. The isolates were obtained from different parts of the plant (flowers, stems and leaves). A total 12 isolates were characterized and identified using molecular biology analysis based on the internal transcribed spacer (ITS) region sequencing. 5 fungal species of endophytic fungi were successfully isolated from Carpobrotus edulis including Trichoderma asperellum, Fusarium culmorum, Penicillium radicum, Aspergillus flavus and 8 isolates represented the same fungal species Aspergillus fumigatus. The 5 fungal species isolated in the current study are reported for the first time as Carpobrotus edulis endophytes.

The plant growth promoting psychrotrophic Bacilli were investigated from different sites in north western Indian Himalayas. A total of 247 morphotypes were obtained from different soil and water samples and were grouped into 43 clusters based on 16S rDNA-RFLP analysis with three restriction endonucleases. Sequencing of representative isolates has revealed that these 43 Bacilli belonged to different species of 11 genera viz., Desemzia, Exiguobacterium, Jeotgalicoccus, Lysinibacillus, Paenibacillus, Planococcus, Pontibacillus, Sinobaca, Sporosarcina, Staphylococcus and Virgibacillus. With an aim to develop microbial inoculants that can perform efficiently at low temperatures, all representative isolates were screened for different plant growth promoting traits at low temperatures (5-15 degrees C). Among the strains, variations were observed for production (%) of indole-3-acetic acid (20), ammonia (19), siderophores (11), gibberellic acid (4) and hydrogen cyanide (2); solubilisation (%...

Background Since the World’s population is increasing, it’s critical to boost agricultural productivity to meet the rising demand for food and reduce poverty. Fertilizers are widely used in traditional agricultural methods to improve crop yield, but they have a number of negative environmental consequences such as nutrient losses, decrease fertility and polluted water and air. Researchers have been focusing on alternative crop fertilizers mechanisms to address these issues in recent years and nanobiofertilizers have frequently been suggested. “Nanophos” is a biofertilizer and contains phosphate-solubilising bacteria that solubilises insoluble phosphate and makes it available to the plants for improved growth and productivity as well as maintain soil health. This study evaluated the impact of nanophos on the growth and development of maize plants and its rhizospheric microbial community such as NPK solubilising microbes, soil enzyme activities and soil protein under field condition a...

Total of 48 endophytic bacterial isolates from soybean (43) and summer mungbean (5) rhizosphere were screened for zinc solubilizing ability in Tris-minimal medium separately amended with inorganic zinc compounds viz. zinc oxide (ZnO) and zinc phosphate Zn3(PO4)2 by plate assay method. Further zinc solubilizing isolates were assessed for morphological, biochemical and plant growth promoting (PGP) traits in vitro. Of 48 endophytic bacterial isolates, 3 and 17 were able to solubilize ZnO whereas 2 and 12 were able to solubilize Zn3(PO4)2 on Tris-minimal medium. Endophytes 1J (Klebsiella spp.) and 19D (Pseudomonas spp.) were found to be promising bacterial isolates as they solubilized both inorganic sources of zinc separately supplemented in Tris-minimal medium along with good PGP traits (P-solubilization & indole acetic acid) and can be exploited as potential biofertilizers.

Khuong, N. Q., Quang, L. T., Thuc, L. V., Huu, T. N., Thu, L. T. M., Van, T. T. B., Xuan, D. T., Hue, N. H., Le, N. T. T., Tien, P. D., Nhan, T. C., Xuan, L. N. T. & Xuan, N. T. T. (2022). Potential of endophytic phosphorus-solubilizing bacteria to improve soil fertility, P uptake, and yield of maize (Zea mays L.) cultivated in alluvial soil in dikes in Vietnam. Bulg. J. Agric. Sci., 28 (2), 217–228 This study aimed to (i) select endophytic bacteria in maize root for its phosphorus solubilization ability and (ii) evaluate the efficacy of selected indigenous bacterial strains on soil fertility, phosphorus (P) uptake, growth, and maize yield. A total of 31 maize root samples were collected from An Phu District, An Giang Province, to isolate the bacteria. In addition, the pot experiment was conducted with nine treatments of (i) 100% P of the recommended fertilizer formula (RFF), (ii) 75% P of the RFF, (iii) 50% P of the RFF, (iv) 25% P of the RFF, (v) 75% P of the RFF plus a mixture of...

Plant-plant chemical interactions in forests can have a strong impact on the biodiversity and dynamics of these ecosystems, particularly in Mediterranean forests where plants exhibit a high secondary metabolite diversity. Allelopathic interactions in Mediterranean ecosystems have been mostly studied in the first stages of ecosystem dynamics, shrublands and pine forests, but little is known about these interactions in mature oak forests. In this study, the allelopathic effect of three main woody species of downy oak forests (Quercus pubescens, Acer monspessulanum and Cotinus coggygria) on germination and growth of two herbaceous species (Festuca ovina and Linum perenne) was tested through aqueous extracts obtained from different leaf phenological stages (green, senescent and litter). The germination velocity of the two target species was inhibited by the aqueous extracts of senescent leaves from all the woody species. The growth of F. ovina seedlings was affected by aqueous extracts of green leaves of all the woody species, while the growth of L. perenne was only affected by aqueous extracts of green leaves of A. monspessulanum. This shows that (i) allelochemicals released by leaf leachates of the dominant woody species could control the dynamic of the herbaceous species, and then their potential competition with trees and (ii) allelopathic effects of woody species are related to their phenological stage and seem consistent with the development stage of target species.

Plants, being sessile organisms are exposed to a variety of biotic and abiotic stresses. Bacteria, living in the rhizosphere of the plants can be beneficial, exhibiting plant growth promotion effect and inducing the stress tolerance of the plant. Therefore, studies regarding the role of plant growth promoting rhizobacteria (PGPR) in the stress management of the plants have received increasing attention. In the present study, we studied the stress tolerance and beneficial trait maintenance of 30 PGPR strains under stress condition. From a total of 17 heavy metal and salt stress tolerant bacterial strains, two Cd and Zn tolerant PGPR strains Viridibacillus sp. (BP13) and Defltia acidovorans (BP12) as well as two salt tolerant strains Pantoea agglomerans (8G/3) and Serratia fonticola (BB17) were selected for plant experiments. When heavy metal and salt stress were applied, the beneficial effect of PGP bacterial inoculation on maize plant growth and development was confirmed only sporadically. Stress mitigation was observed in the case of Viridibacillus sp. (BP13) and Defltia acidovorans (BP12) strains (0.1 mM Cd treatment), Serratia fonticola (BB17) (until 3 g/L NaCl) and Pantoea agglomerans (8G/3) (5 g/L NaCl). Despite the sporadically observed beneficial effect of the PGP bacterial inoculation on plant growth and development; a higher guaiacol peroxidase (GPOX) activity observed under Viridibacillus sp. (BP13) bacterial inoculation in the presence of heavy metal stress, as well as Pantoea agglomerans (8G/3) and Serratia fonticola (BB17) inoculation in the case of salt stress revealed that PGP bacterial strains increased the plant tolerance to abiotic stressors.

Plants, being sessile organisms are exposed to a variety of biotic and abiotic stresses. Bacteria, living in the rhizosphere of the plants can be beneficial, exhibiting plant growth promotion effect and inducing the stress tolerance of the plant. Therefore, studies regarding the role of plant growth promoting rhizobacteria (PGPR) in the stress management of the plants have received increasing attention. In the present study, we studied the stress tolerance and beneficial trait maintenance of 30 PGPR strains under stress condition. From a total of 17 heavy metal and salt stress tolerant bacterial strains, two Cd and Zn tolerant PGPR strains Viridibacillus sp. (BP13) and Defltia acidovorans (BP12) as well as two salt tolerant strains Pantoea agglomerans (8G/3) and Serratia fonticola (BB17) were selected for plant experiments. When heavy metal and salt stress were applied, the beneficial effect of PGP bacterial inoculation on maize plant growth and development was confirmed only sporadically. Stress mitigation was observed in the case of Viridibacillus sp. (BP13) and Defltia acidovorans (BP12) strains (0.1 mM Cd treatment), Serratia fonticola (BB17) (until 3 g/L NaCl) and Pantoea agglomerans (8G/3) (5 g/L NaCl). Despite the sporadically observed beneficial effect of the PGP bacterial inoculation on plant growth and development; a higher guaiacol peroxidase (GPOX) activity observed under Viridibacillus sp. (BP13) bacterial inoculation in the presence of heavy metal stress, as well as Pantoea agglomerans (8G/3) and Serratia fonticola (BB17) inoculation in the case of salt stress revealed that PGP bacterial strains increased the plant tolerance to abiotic stressors.

Certain rhizobacteria can be applied to remove arsenic in the environment through bioremediation or phytoremediation. This study determines the minimum inhibitory concentration (MIC) of arsenic on identified rhizobacteria that were isolated from the roots of Ludwigia octovalvis (Jacq.) Raven. The arsenic biosorption capability of the was also analyzed. Among the 10 isolated rhizobacteria, five were Gram-positive (Arthrobacter globiformis, Bacillus megaterium, Bacillus cereus, Bacillus pumilus, and Staphylococcus lentus), and five were Gram-negative (Enterobacter asburiae, Sphingomonas paucimobilis, Pantoea spp., Rhizobium rhizogenes, and Rhizobium radiobacter). R. radiobacter showed the highest MIC of >1,500 mg/L of arsenic. All the rhizobacteria were capable of absorbing arsenic, and S. paucimobilis showed the highest arsenic biosorption capability (146.4 ± 23.4 mg/g dry cell weight). Kinetic rate analysis showed that B. cereus followed the pore diffusion model (R2 = 0.86), E. a...

The present investigation was carried out during 2021-22 at Acharya Narendra Deva University of Agriculture & Technology, Kumarganj, Ayodhya (Uttar Pradesh). Results revealed that phenotypic characterization of plant growth promoting microbial isolates from rice rhizosphere and phyllosphere have significant effects on physicochemical properties of soil. On the other hand, microbial isolates have a significant effect on microbial biomass carbon (MBC) and total protein content of the soil. Applying microbial isolates has a positive impact on microbial population in terms of total rhizospheric bacterial population (0.77-8.4×10 6 cfu g-1 soil). Whereas, fungal population (1.0-51.0 ×10 3 sfu g-1 and actinomycetes (1.7-97 ×10 3 cfu g-1 of soil). Whereas, total number of phyllospheric bacterial population of rice plant leaves and clumps were 0.53-6.4×10 6 cfu Original Research Article-1. The isolated microorganisms can be used as an effective bio inoculant either individually or in different combinations for the formulation of different multi potent biofertilizers for plant growth promotion substances as well as control of plant diseases in rice crop.

Many rhizosphere microorganisms solubilize the fixed phosphorus present in soil and make it available to the plants and also contribute towards better growth and yield of plants through other direct and indirect plant growth promoting activities. This communication deals with synergistic effect and compatibility of two rhizosphere microorganisms, Pseudomonas fluorescens BAM-4 and Aspergillus awamori S-19 in vitro and in planta in chickpea. BAM-4 and S-19 solubilized 354.41 and 361.12 mg kg−1 of P in vitro, respectively. BAM-4 also showed indole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Under pot culture conditions, the overall plant growth in all treatments assayed increased significantly over the untreated soil. The length and fresh and dry weight of plants were significantly higher in co-inoculation treatment by BAM-4 and S-19 as compared to single inoculation of either microorganism, showing the positive synergistic effect. The n...

Plant Growth Promoting Rhizobacteria (PGPR) represent a heterogeneous group of bacteria, which have been characterized for their ability to influence the growth and the fitness of agricultural plants. In the quest of more sustainable practices, PGPR have been suggested as a valid complement for the agronomical practices, since they can influence several biochemical and molecular mechanisms related to the mineral nutrients uptake, the plant pathogens suppression, and the phytohormones production. Within the present work, three bacterial strains, namely Enterobacter asburiae BFD160, Pseudomonas koreensis TFD26, and Pseudomonas lini BFS112, previously characterized on the basis of distinctive PGPR traits, were tested to evaluate: (i) their persistence in soil microcosms; (ii) their effects on seeds germination; (iii) their possible influence on biochemical and physiological parameters related to plant growth, fruit quality, and plant nutrient acquisition and allocation. To these aims, ...

In search of an effective biological control agent against the tomato pathogen Fusarium oxysporum f. sp. lycopersici, rhizospheric soil samples were collected from eight agro-ecological zones of Bangladesh. Among the bacteria isolated from soil, 24 isolates were randomly selected and evaluated for their antagonistic activity against F. oxysporum f. sp. lycopersici. The two promising antagonistic isolates were identified as Brevundimonas olei and Bacillus methylotrophicus based on morphological, biochemical and molecular characteristics. These two isolates were evaluated for their biocontrol activity and growth promotion of two tomato cultivars (cv. Pusa Rubi and Ratan) for two consecutive years. Treatment of Pusa Rubi and Ratan seeds with B. olei prior to inoculation of pathogen caused 44.99% and 41.91% disease inhibition respectively compared to the untreated but pathogen-inoculated control plants. However, treatment of Pusa Rubi and Ratan seeds with B. methylotrophicus caused 24.99% and 39.20% disease inhibition respectively. Furthermore, both the isolates enhanced the growth of tomato plants. The study revealed that these indigenous bacterial isolates can be used as an effective biocontrol agent against Fusarium wilt of tomato.