Plant Growth-promoting Endophytic Bacteria Research Articles

The functional identification and evaluation of endophytic bacteria sourced from the roots of tolerant Achyranthes bidentata to overcome monoculture problems of Rehmannia glutinosa

The isolation and identification of plant growth-promoting endophytic bacteria (PGPEB) from Achyranthes bidentata roots have profound theoretical and practical implications in ecological agriculture, particularly as bio-inoculants to address challenges associated with continuous monoculture. Our research revealed a significant increase in the abundance of these beneficial bacteria in A. bidentata rhizosphere soil under prolonged monoculture conditions, as shown by bioinformatics analysis. Subsequently, we isolated 563 strains of endophytic bacteria from A. bidentata roots. Functional characterization highlighted diverse plant growth-promoting traits among these bacteria, including the secretion of indole-3-acetic acid (IAA) ranging from 68.01 to 73.25 mg/L, phosphorus and potassium solubilization capacities, and antagonistic activity against pathogenic fungi (21.54%−50.81%). Through 16S rDNA sequencing, we identified nine strains exhibiting biocontrol and growth-promoting potential. Introduction of a synthetic microbial consortium (SMC) in pot experiments significantly increased root biomass by 48.19% in A. bidentata and 27.01% in replanted Rehmannia glutinosa. These findings provide innovative insights and strategies for addressing continuous cropping challenges, highlighting the practical promise of PGPEB from A. bidentata in ecological agriculture to overcome replanting obstacles for non-host plants like R. glutinosa, thereby promoting robust growth in medicinal plants.

Effect of biopriming and nanopriming on physio-biochemical characteristics of Cicer arietinum L. under drought stress

Drought, a detrimental abiotic stress, disturbs many vital processes critical to plant growth and development resulting in subpar crop yield. Unconventional measures such as biofertilizers and nanofertilizers have been reported as reliable solutions to this, however, outcomes vary greatly depending upon the type of organism/particle and its mode of delivery. Seed priming involves treating seeds with organic/inorganic chemicals to ameliorate drought stress by boosting pre-germinative metabolism, maintaining water potential, scavenging free radicals, etc. Therefore, this study determined the effect of biopriming and nanopriming on germination percentage (GP), leaf water status (LWS), proline, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and survial percentage (SP) of BG-4958 (Drought tolerant) and ICC-1882 (Drought sensitive) chickpea varieties exposed to polyethylene glycol (PEG) induced moderate (5 %) and severe drought (10 %) at flowering with no drought acting as a control. Experimental setup had three groups, control (untreated), bioprimed with plant growth promoting endophytic bacteria (PGPEB), and nanoprimed with CuNPs synthesised from PGPEB and their chemical counterparts). Crop analysis after 15 DDS (Days to drought stress) revealed that priming significantly altered the physio-biochemical parameters. Consortium and N2X led highest increment in GP and SP for DT and DS varieties, respectively, whereas N1X showed highest increase in LWS of both. Highest accumulation of proline was observed with consortium and N1 (X & Y) in DS variety while only biological CuNPs accumulated proline for DT variety. MDA and H₂O₂ decreased significantly in treated groups thereby reducing oxidative damage with non-significant variations in DT. Lower concentrations of biological CuNPs were found to be more effective in modulating the physio-biochemical machinery of chickpea under drought than their higher concentration as well as chemical counterparts. This study deepens our understanding of the beneficial role of PGPEB and biosynthesized CuNPs in alleviating the adverse effects of drought in chickpea.

Bacillus subtilis 26D Triggers Induced Systemic Resistance against Rhopalosiphum padi L. by Regulating the Expression of Genes AGO, DCL and microRNA in Bread Spring Wheat.

Bacillus subtilis 26D is a plant growth-promoting endophytic bacteria capable of inducing systemic resistance through the priming mechanism, which includes plant genome reprogramming and the phenomenon of RNA interference (RNAi) and microRNA (miRNAs). The phloem-feeding insect bird cherry-oat aphid Rhopalosiphum padi L. is a serious pest that causes significant damage to crops throughout the world. However, the function of plant miRNAs in the response to aphid infestation remains unclear. The results of this work showed that B. subtilis 26D stimulated aphid resistance in wheat plants, inducing the expression of genes of hormonal signaling pathways ICS, WRKY13, PR1, ACS, EIN3, PR3, and ABI5. In addition, B. subtilis 26D activated the RNAi mechanism and regulated the expression of nine conserved miRNAs through activation of the ethylene, salicylic acid (SA), and abscisic acid (ABA) signaling pathways, which was demonstrated by using treatments with phytohormones. Treatment of plants with SA, ethylene, and ABA acted in a similar manner to B. subtilis 26D on induction of the expression of the AGO4, AGO5 and DCL2, DCL4 genes, as well as the expression of nine conserved miRNAs. Different patterns of miRNA expression were found in aphid-infested plants and in plants treated with B. subtilis 26D or SA, ethylene, and ABA and infested by aphids, suggesting that miRNAs play multiple roles in the plant response to phloem-feeding insects, associated with effects on hormonal signaling pathways, redox metabolism, and the synthesis of secondary metabolites. Our study provides new data to further elucidate the fine mechanisms of bacterial-induced priming. However, further extensive work is needed to fully unravel these mechanisms.

Isolation, screening, and characterization of plant growth enhancing endophytic bacteria from halophytic Heliotropium curassavicum L. collected from salt stress areas of Srikakulam, Andhra Pradesh

Farmers use excessive chemical fertilizers to boost crop productivity to meet growing agricultural demands. However, this practice is costly and environmentally hazardous. Sustainable increase in crop yield can be achieved through alternatives like microbial-based fertilizers. In the quest to identify plant growth-promoting endophytic bacteria, the present study was carried out and selected unexplored halophytic plant Heliotropium curassavicum L. Thirteen endophytic bacterial strains were isolated from both aerial and root portions of H.curassavicum. These isolates were tested for salt tolerance, enzyme production, and synthesis of growth-promoting secondary metabolites, like Indole-3-acetic acid (IAA) and phosphate solubilization . Most of the isolates belonged to the Bacillus family, exhibiting varying Gram staining and biochemical reactions. The majority are Gram-positive bacteria, non-motile, spore formers, and exist in two cells or chains. All isolates could tolerate up to 10% NaCl concentration and a temperature of 42°C. Based on phenotypic, bio-chemical characteristics, isolate HCR3 showed promising properties in synthesizing IAA and phosphate solubilization abilities. The isolate HCR3 grew well upto 10% NaCl concentration and also 42°C temperature. Based on molecular characterization by using 16S rRNA gene-based analysis HCR3 isolate was identified and belonged to the Genus Pseudomonas with the highest similarity index with Pseudomonas khazarica sp. HCR3 showed IAA production of 37µg ml-1, had a phosphate solubilization ability of 3.5 ppm, and recorded protease activity on gelatin medium. The findings highlight the potential of HCR3 and other strains from halophytic H. curassavicum L. to enhance plant growth through secondary bioactive metabolites, offering eco-friendly solutions for sustainable agriculture.

ENDOPHYTIC BACTERIA FROM BANANA PLANT IMPROVES THE GROWTH AND YIELD OF BLACK RICE PLANT

Three bacterial isolates selected as plant growth-promoting endophytic bacteria (PGPEB) from “Klutuk” banana (Musa balbisiana L.) gained scrutiny for first-time testing on black rice. The presented study pursued an investigation on the impact of endophytic bacteria inoculation obtained from “Klutuk” banana plants on the growth and production traits of black rice. For this research, the three bacterial isolates (K10, K324, and K111) served as inoculums for black rice seeds, testing for synergism. The three isolates inoculation into black rice plants used both single and consortium inoculation methods. With agar media, black rice growth observation began 14 days after plantation (DAP) while on soil, at 30 and 140 DAP with inoculation. Three isolates did not show any antagonistic reactions. Overall, isolate K10 showed less significant improvement in growth and yield traits of black rice compared with two other isolates, i.e., K324 and K111. With agar media, the endophytic bacteria inoculations did not show a significant effect on the growth of black rice, and even isolate K324 was inhibiting in action. However, on soil media, isolate K324 significantly enhanced the number of roots and shoot length in black rice compared with the control at 30 DAP. The single inoculation with isolate K111 has caused increased productivity based on the weight of the root, dry grain weight per clum, plant height, root length, leaf length, and panicle length in black rice. Isolate K324 promotes the growth of black rice on the soil media at 30 DAP, while isolate K111 improves the production traits on the soil media at 140 DAP. The study findings provide a significant basis for the positive impact of endophytic bacterial inoculation on black rice growth and yield traits.

Plant growth-promoting endophytic bacteria isolated from Launaea arborescens (characterization and molecular identification)

The present investigation aimed to assess endophytic bacteria's capacity to stimulate plant development. Eight endophytic bacterial strains were isolated from the root of Launaea arborescens (Batt.), native medicinal plant growing spontaneously in the region of Bechar (south-west Algeria). The eight strains were tested for their effects on seed germination and plant growth of Triticum aestivum L. The results showed that all strains had positive effects on wheat seeds germination. The seeds inoculation of wheat by endophytic bacteria improves morphological parameters of the seedling (fresh and dry weight of plant, root and stem elongation). 16S rRNA gene sequencing was used to identify the powerful strain, it was found as Brevibacillus brevis. This one was found positive for many of the plant growth promoting attributes like ammonia production and azote fixing. In addition, it was identified as resistant to azithromycine during antibiotic sensitivity test and It could tolerate up to 0.9 M of NaCl. Additionally, Brevibacillus brevis was identified as resistant in the herbicide and the insecticide susceptibility test. Results suggest that this endophyte is a strong candidate for use as plant growth-promoting inoculants, to assist in lowering the amount of chemicals used in agricultural practices and enhance nutrient absorption and stress resistance in plant species.

Seeds of Stevia rebaudiana Bertoni as a Source of Plant Growth-Promoting Endophytic Bacteria with the Potential to Synthesize Rebaudioside A.

In this study, a new strain of Pantoea vagans, SRS89, was isolated from surface-sterilized stevia seeds. The isolate was evaluated using morphological, molecular, and biochemical methods. The bacterium was 1.5 μm long, yellowish in color, and classified as Gram-negative. Whole genome sequencing of our strain revealed the presence of a 4,610,019 bp chromosome, and genome annotation resulted in the detection of 4283 genes encoding 4204 putative coding sequences. Phylogenic analysis classified the genome of our strain close to the MP7 and LMG 24199 strains of P. vagans. Functional analysis showed that the highest number of genes within the analyzed bacterium genome were involved in transcription, amino acid transport and metabolism, and carbohydrate transport and metabolism. We also identified genes for enzymes involved in the biosynthesis of carotenoids and terpenoids. Furthermore, we showed the presence of growth regulators, with the highest amount noted for gibberellic acid A3, indole-3-acetic acid, and benzoic acid. However, the most promising property of this strain is its ability to synthesize rebaudioside A; the estimated amount quantified using reversed-phase (RP)-HPLC was 4.39 mg/g of the dry weight of the bacteria culture. The isolated endophytic bacterium may be an interesting new approach to the production of this valuable metabolite.

Halophytic Plant Halostachys belangeriana (Moq.) Botsch as a Source of Plant Growth-Promoting Endophytic Bacteria

Halostachys belangeriana (Moq.) Botsch also known as Halostachys caspica C. A. Mey belongs to the Chenopodiaceae family and is distributed in deserts of Asian countries. The plant grows in severe salinity and drought conditions and its survival and growth can be associated with the activity of endophytic bacteria. The objective of our research was to isolate and screen endophytic bacteria from Halostachys belangeriana for plant growth promotion and reveal their plant-beneficial traits. Methods. Halostachys belangeriana (Moq.) Botsch plants were collected from the saline soil of the Kyzylkum desert in Uzbekistan in spring. The endophytic bacteria were isolated from the tissues of plants by cutting the outer sterilized shoots and roots and putting them into the water to let bacteria come from the tissues into the water. The suspension was transferred onto Tryptic Soy Agar to let bacteria grow and form separate colonies. The colonies different in shape and color were used to get pure cultures of bacteria. The bacteria were screened using plant growth-promoting activity in Petri plates by inoculating wheat seeds with the suspension of isolated bacteria. The best plant growth promoters were identified by analyzing their 16S rRNA gene and comparing it with sequences registered in GenBank of NCBI. The strains were tested for wheat growth promotion in a pot experiment and then examined for their plant-benefi cial traits: N2-fixation, phosphates solubilization, production of indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate deaminase (ACC-deaminase), and siderophores. Results. A total of 25 isolates of endophytic bacteria were obtained from the tissues of Halostachys belangeriana (Moq.) Botsch. Due to the high efficiency of isolates SSU-4, SSU-7, SSU-16, SSU-18, and SSU-21 in the stimulation of wheat shoot and root growth, they were chosen for identification and (OK559720), Bacillus endophyticus SSU-7 (OK559721), Bacillus subtilis SSU-16 (OK559722), Isoptericola halotolerans SSU-18 (OK559723) and Pseudomonas kilonensis SSU-21 (OK559724), respectively. The single inoculation of seeds with tested strains increased the root and shoot length and plant fresh weight. The coinoculation of seeds with a mixture of five strains resulted in an even more increase in plant growth parameters. It was revealed that the tested strains had at least two plant-beneficial properties. The strains B. pumilus SSU-4 and P. kilonensis SSU-21 had the ability for nitrogen fixation. All strains produced IAA; however, the most active IAA producer was P. kilonensis SSU-21. Three of five strains had phosphates solubilization ability and produced ACC-deaminase and siderophores. The strains B. pumilus SSU-4 and P. kilonensis SSU-21 possessed four of five tested plant-beneficial properties. The strains B. endophyticus SSU-7 and I. halotolerans SSU-18 had three of five tested plant-beneficial traits, and B. subtilis SSU-16 could just produce IAA and ACC-deaminase. Conclusions. This is the first report about the isolation of plant growth-promoting endophytic bacteria from the desert halophytic plant Halostachys belangeriana (Moq.) Botsch. The most efficient plant growth-promoting strains were: B. pumilus SSU-4, B. endophyticus SSU-7, B. subtilis SSU-16, I. halotolerans SSU-18, and P. kilonensis SSU-21. After field experiments, these strains can be suggested for use as bioinoculants improving plants growth.

Screening of plant growth-promoting endophytic bacteria from the maize roots for biocontrol of stewart wilt disease

Bacterial endophytes colonize and are widely related to plant interior tissues. They provide maize with various advantages by functioning as growth stimulants and disease protectors. This research is intended to verify the hypothesis that the maize root bacteria are potential plant growth-promoting and Stewart wilt disease-suppressor. Fifty-three endophytic root bacteria from various maize varieties cultivated in South Sumatra and West Java production centres were isolated and evaluated. Initial screening for biosafety assays has selected 24 isolates for further analysis. The antagonistic activity of a bacterial endophyte against Pantoea stewartii subsp. stewartii was evaluated. Endophytic bacteria were selected for indole-3-acetic acid (IAA) synthesizing, nitrogen fixation, solubilizer-phosphate capacity, lytic-enzymes production, and pathogens inhibition. Antibiotics were produced by approximately 50% of isolates, volatile organic compounds by more than 80% of isolates, IAA by up to 91.7% of isolates, N fixation by 79.2% of isolates, phosphate solubilization by more than 50% of isolates, and protease by only 20.8% of isolates. Six isolates have been successfully selected using the analytical hierarchy process (AHP), which have a maximum score of AHP, including BU-5, JCJ-7, MS-X, JCB-1, JCJ-3, and JCJ-2. The highest inhibition of pathogen growth through antimicrobial activity occurs in isolates BU-5 and JCJ-7 (100%), while JCJ-2 has maximum VOC activity (80.56%) and IAA production (32.78 ppm). Meanwhile, solubilizing phosphate index and protease production are the highest in the JCJ-3 isolate. This paper offers scientific information for upcoming studies on endophytic bacteria to increase maize productivity and disease control.

The influence of Bacillus subtilis 10-4 on the hormonal system and water regime balance of wheat plants under dehydration

The work was devoted to the study of the influence of endophytic plant growth-promoting bacteria (PGPB) Bacillus subtilis strain 10-4 on wheat plants Triticum aestivum L. subjected to dehydration, induced by 12% PEG. Presowing seed treatment with endophytes at the concentration of 105 CFU mL−1 had stimulating and protective effects on the wheat plants growth under normal and stress conditions, respectively, which was judged on biomass accumulation, linear dimensions and visual appearance of the seedlings. The positive action of PGPB may be determined by the effects on the wheat hormonal system, as indicated by the data on increasing in the seedlings of the auxins content under normal conditions and prevention of its reduction under stress. PGPB-pretreatment decreased the stress-induced levels of abscisic acid (ABA) accumulation and cytokinin (CK) content diminution in the seedlings. Moreover the protective effect of B. subtilis 10-4 can be determined by their stabilizing effects on the membrane cell structures and water regime balance of wheat plants under dehydration.

Whole genome analysis for plant growth promotion profiling of Pantoea agglomerans CPHN2, a non-rhizobial nodule endophyte.

Reduced agricultural production as well as issues like nutrient-depleted soils, eutrophication, and groundwater contamination have drawn attention to the use of endophyte-based bioformulations to restore soil fertility. Pantoea agglomerans CPHN2, a non-rhizobial nodule endophyte isolated from Cicer arietinum, exhibited a variety of plant growth-promoting traits. In this study, we used NextSeq500 technology to analyze whole-genome sequence information of this plant growth-promoting endophytic bacteria. The genome of P. agglomerans CPHN2 has a length of 4,839,532 bp and a G + C content of 55.2%. The whole genome comprises three different genomic fractions, comprising one circular chromosome and two circular plasmids. A comparative analysis between P. agglomerans CPHN2 and 10 genetically similar strains was performed using a bacterial pan-genome pipeline. All the predicted and annotated gene sequences for plant growth promotions (PGPs), such as phosphate solubilization, siderophore synthesis, nitrogen metabolism, and indole-3-acetic acid (IAA) of P. agglomerans CPHN2, were identified. The whole-genome analysis of P. agglomerans CPHN2 provides an insight into the mechanisms underlying PGP by endophytes and its potential applications as a biofertilizer.

Endophytic bacteria performs better than endophytic fungi in improving plant growth under drought stress: A meta-comparison spanning 12 years (2010-2021).

Drought stress is a serious issue that affects agricultural productivity all around the world. Several researchers have reported using plant growth-promoting endophytic bacteria to enhance the drought resistance of crops. However, how endophytic bacteria and endophytic fungi are effectively stimulating plant growth under drought stress is still largely unknown. In this paper, a global meta-analysis was undertaken to compare the plant growth-promoting effects of bacterial and fungal endophytes and to identify the processes by which both types of endophytes stimulate plant growth under drought stress. Moreover, this meta-analysis enlightens how plant growth promotion varies across crop types (C3 vs. C4 and monocot vs. dicot), experiment types (in vitro vs. pots vs. field), and the inoculation methods (seed vs. seedling). Specifically, this research included 75 peer-reviewed publications, 170 experiments, 20 distinct bacterial genera, and eight fungal classes. On average, both endophytic bacterial and fungal inoculation increased plant dry and fresh biomass under drought stress. The effect of endophytic bacterial inoculation on plant dry biomass, shoot dry biomass, root length, photosynthetic rate, leaf area, and gibberellins productions were at least two times greater than that of fungal inoculation. In addition, under drought stress, bacterial inoculation increased the proline content of C4 plants. Overall, the findings of this meta-analysis indicate that both endophytic bacterial and fungal inoculation of plants is beneficial under drought conditions, but the extent of benefit is higher with endophytic bacteria inoculation but it varies across crop type, experiment type, and inoculation method. This article is protected by copyright. All rights reserved.

Abundant and diverse endophytic bacteria associated with medicinal plant Arctium lappa L. and their potential for host plant growth promoting.

Arctium lappa L. is one of the medicinal and food homologous plants in China, which is rich in nutrients and medicinal ingredients. The use of plant growth-promoting (PGP) endophytic bacteria is an alternative to reducing chemical fertilizers in agricultural production. The aim of this study was to analyze the diversity of endophytic bacteria in different cultivars of A. lappa L. collected from two geographical locations in China and evaluate PGP traits of the isolates and their potential PGP ability in greenhouse condition. Endophytic bacterial community was investigated by culture-dependent and culture-independent methods. Isolates were screened and investigated for multiple PGP traits, and representative strains were inoculated host seedlings to evaluate the growth promoting effect. A total of 348 endophytic bacteria were obtained and they were distributed into 4 phyla and 30 genera. In addition, highthroughputsequencing revealed more abundant bacterial community, including 17 bacterial phyla and 207 genera. A high proportion of PGP traits were detected, including production of indole acetic acid, siderophore, ammonia and phosphate solubilization. Four representative strains with multiple PGP traits of the most dominant genera (Bacillus, Pantoea, Microbacterium and Pseudomonas) were further selected for host inoculation and growth promoting evaluation, and they significantly increase seedlings length, root length and fresh weight. This study demonstrated that A. lappa L. harbors abundant endophytic bacteria, and some endophytic bacteria showed good potential for the development of microbial fertilizer in the future.

Бактеріальні ендофіти пшениці та їхня роль у покращенні мікроелементного складу зерна

In sustainable agriculture, there is a tendency for an increased use of microbiological preparations, especially plant growth promoting bacteria (PGPB), that can supplement the phenotypic plasticity and adaptability of plants, stimulate their growth and development, increase resistance to stress. The endophytic PGPB could be a promising element of technologies for the improvement of mineral nutrition and promotion of growth and yield of wheat (Triticum spp.). They are transferred to the plant by a horizontal, from the environment (rhizosphere, phyllosphere), or a vertical, from the seeds (from generation to generation), way. The growth-promoting effect of endophytes is mediated by the synthesis and secretion of phytohormones and secondary metabolites as well as their ability to absorb N2, suppress the development of bacterial and/or fungal phytopathogens; improve mineral nutrition. The review elucidates current data on the presence of bacterial endophytes in various organs of wheat plants and their characterization as potential PGPB. Data on the most common genera of bacterial endophytes of wheat (Bacillus, Micrococcus, Staphylococcus, Pseudomonas, Pantoea, Kosakonia, etc.) are presented, and their influence on plants is described, in particular, the effect on the absorption of micronutrients important for plants and humans such as iron (Fe) and zinc (Zn), resistance to stress factors and growth. The varietal differences in the wheat endophytic microbiome are noted. An increased micronutrient absorption and assimilation assisted by the bacterial endophytes are associated with the changes in endogenous auxins and ethylene, the release of organic acids, siderophores, indirect activation of metal transporters, etc. The mechanisms underlying plant growth stimulation are complex due to interactions between a microorganism and the whole plant microbiome and their changes during the plant ontogenesis. The analysis of the published data confirms the need for further studies of the species composition and mechanisms of interaction of endophytic PGPB to develop new strategies for improving mineral nutrition of wheat and trace element biofortification of grain. It is a feasible and promising technology of the future to overcome the problems of hidden hunger and provide quality food products to the world population with available resources and a reduced negative impact on the environment.

Chickpea (Cicer arietinum L.) Seeds as a Reservoir of Endophytic Plant Growth-Promoting Bacteria.

The seed microbiome, the primary source of inoculum for plants, may play an important role in plant growth, health and productivity. However, the structure and function of chickpea seed endophytes are poorly characterized. Bacteria with beneficial characteristics can be selected by the plant and transmitted vertically via the seed to benefit the next generation. Studying the diversity and multifunctionality of seed microbial communities can provide innovative opportunities in the field of plant-microbe interaction. This study aimed to isolate, identify and characterize culturable endophytic bacteria from chickpea (Cicer arietinum L.) seeds. Phylogenetic analysis based on 16S rDNA showed that the endophytic bacteria belong to the genera Mesorhizobium, Burkholderia, Bacillus, Priestia, Paenibacillus, Alcaligenes, Acinetobacter, Rahnella, Enterobacter, Tsukamurella, and Microbacterium. The most frequently observed genus was Bacillus; however, rhizobia typically associated with chickpea roots were also found, which is a novel finding of this study. Siderophore production and phosphorus solubilization were the most widespread plant growth-promoting features, while hydrogen cyanide production was relatively rare among the isolates. Most of the isolates possess two or more plant growth-promoting features; however, only Bacillus thuringiensis Y2B, a well-known entomopathogenic bacteria, exhibited the presence of all plant growth-promoting traits evaluated. Results suggest that endophytic bacteria such as Bacillus, Mesorhizobium, and Burkholderia may be vertically transferred from inoculated plants to seeds to benefit the next generation.

Characterization and identification of plant growth promoting endophytic bacterial strain IU10

Growing evidence has suggested that plant growth-promoting endophytic bacteria can regulate, which can be used as biofertilizers, bio-stimulants, and biocontrol agent. In the present study, Bacillus subtills IU10 was isolated from plants and was subjected to advanced chromatography and spectroscopic techniques for the extraction and isolation of indole-3-acetic acid (IAA). Up to 10 ?g/mL of IAA was quantified in the bacterial extract using the [2H2]-IAA internal standards in GC-MS analysis. PVK agar containing Ca3(PO4)2 was used to measure the ability of IU10 to solubilize phosphate. The clear zones formed by phosphate solubilization were measured to assess the phosphate solubilization potential. Azurol-S (CAS) medium was used for measuring siderophore production. The orange halo circles were measured to quantify the siderophore production. Endophytic IU10 inoculated plants showed significantly improvement root to shoot length, biomass and chlorophyll as compared to control. The data indicates that IU10 produce phytohormones, siderophore and immobilize nutrients could be used as biofertilizer. Keywords: phytohormones, nutrient immobilization, growth promotion, endophytes.

Exploration of plant growth-promoting endophytic bacteria from the crops grown in sodic soils

Isolation of the potential endophytic bacteria from plants that are grown in sodic soils, their diversity and screening their plant growth-promoting activities for testing their efficiency as bio inoculants for the problem soils were studied. Twelve different isolates were selected out of 35 endophytic bacterial isolates on the basis of their richness in the endophytic population of different crop plants and the nucleotide sequences of 16S rRNA genes were observed. The endophytic bacteria for their plant growth-promoting traits such as nitrogen fixation, IAA production, ACC deaminase production, phosphate solubilization, siderophore secretion and antifungal activity were assessed. The best performing strains were evaluated using principal component analysis (PCA). The phylogenetic tree from the endophytic bacterial isolates of different crops grown in sodic soil was categorized into three clusters i.e. Firmicutes, β-Proteobacteria and γ- Proteobacteria. The PCA results identified two potential endophytic strains viz., Ma11 (Bacillus mojavensis) and Ri 2 (Pseudomonas fluorescens) from sodic soil-grown crops. The present findings revealed that the isolates, Ma 11 and Ri 2 were capable of improving crop growth under sodicity. These multifaceted endophytic bacterial isolates would be developed as new inoculants which will be highly suitable for sodic soils. Bangladesh J. Bot. 51(2): 271-280, 2022 (June)

Plant organ- and growth stage-diversity of endophytic bacteria with potential as biofertilisers isolated from wheat (Triticum aestivum L.)

BackgroundChemical fertilisers are extensively used for crop production, which may cause soil deterioration and water pollution. Endophytic bacteria with plant-growth-promoting (PGP) activities may provide a solution to sustainably improve crop yields, including in-demand staples such as wheat. However, the diversity of the PGP endophytic bacteria in wheat across plant organs and growth stages has not been thoroughly characterised.ResultsHere, we report the isolation of endophytic bacteria from root, stem, leaf and seed of three winter wheat varieties at tillering, jointing, heading and seed-filling growth stages that were identified via 16S rRNA gene sequence analysis. Strains were screened for indole-3-acetic acid (IAA) production, potassium and phosphate solubilisation and the ability to grow on a nitrogen-free medium. Strain's capacity to stimulate various plant growth parameters, such as dry root weight, dry above-ground parts weight and plant height, was evaluated in pot trials. A total of 127 strains were randomly selected from 610 isolated endophytic bacterial cultures, representing ten genera and 22 taxa. Some taxa were organ-specific; others were growth-stage-specific. Bacillus aryabhattai, B. stratosphericus, Leclercia adecarboxylata and Pseudomonas oryzihabitans were detected as wheat endophytes for the first time. The IAA production, inorganic phosphorous solubilisation, organic phosphorus solubilisation, potassium solubilisation and growth on N-free medium were detected in 45%, 29%, 37%, 2.4% and 37.8% of the 127 strains, respectively. In pot trials, each strain showed variable effects on inoculated wheat plants regarding the evaluated growth parameters.ConclusionsWheat endophytic bacteria showed organ- and growth-stage diversity, which may reflect their adaptations to different plant tissues and seasonal variations, and differed in their PGP abilities. Bacillus was the most predominant bacterial taxa isolated from winter wheat plants. Our study confirmed wheat root as the best reservoir for screening endophytic bacteria with potential as biofertilisers.

Exploration of plant growth-promoting endophytic bacteria from Pisum sativum and Cicer arietinum from South-West Haryana.

In the present study, nonrhizobial endophytes were isolated from Pisum sativum and Cicer arietinum from Haryana, India. A total of 355 bacterial endophytes were screened for plant growth promoting traits. Out of all, 96 bacterial endophytes were selected based on morphological characters and multi-PGP traits, and their diversity analyzed by amplified ribosomal DNA restriction analysis. Based on their ARDRA profile, the 25 representative isolates (12 from P. sativum and 13 from C. arietinum), were selected and identified by 16S ribosomal DNA sequencing. Genetic relatedness based on BLAST analysis revealed the similarity of these isolates with members of three prominent phyla, that is, Proteobacteria, Firmicutes, and Actinobacteria. The dominant cluster, Firmicutes, constituted 60% of the isolates, assigned to four different genera, Bacillus, Staphylococcus, Ornithinibacillus, and Lysinibacillus. Phylum α-proteobacteria included two genera, namely Paenochrobactrum and Ochrobactrum and three genera in phylum γ-proteobacteria, namely Pseudomonas, Pantoea and Proteus. The phylum Actinobacteria was constituted of two genera, Microbacterium and Arthrobacter. Bacillus zhangzhouensis, Bacillus safensis, Arthrobacter enclensis from P. sativum and Bacillus haynesii, Paenochrobactrum sp. from C. arietinum are documented as plant growth promoting endophytic bacteria for the first time in the present study. The in vitro and in vivo assessment based on bonitur score revealed that the endophytic isolates Bacillus mojavensis PRN2, Pseudomonas chlororaphis PHN9, B. safensis PRER2, Pseudomonas sp. RCP1, Pseudomonas lini PRN1 and B. haynensii RCP3 from P. sativum and C. arietinum significantly enhanced the plant growth parameters. Therefore, these potential isolates can be further harnessed for preparation of bioformulations to enhance sustainable agriculture.

Biopriming of Durum Wheat Seeds with Endophytic Diazotrophic Bacteria Enhances Tolerance to Fusarium Head Blight and Salinity.

There is growing interest in the use of bio inoculants based on plant growth-promoting bacteria (PGPB) to promote plant growth under biotic and abiotic stresses. Here, we provided a detailed account of the effectiveness of a number of endophytic PGPB strains, isolated from the roots of the halophyte Salicornia brachiata in promoting durum wheat growth and enhancing its tolerance to salinity and fusarium head blight (FHB) disease. Bacillus spp. strains MA9, MA14, MA17, and MA19 were found to have PGPB characteristics as they produced indole-3-acetic acid, siderophores, and lytic enzymes, fixed free atmospheric nitrogen, and solubilized inorganic phosphate in vitro. Additionally, the in vivo study that involved in planta inoculation assays under control and stress conditions indicated that all PGPB strains significantly (p < 0.05) increased the total plant length, dry weight, root area, seed weight, and nitrogen, protein, and mineral contents. Particularly, the MA17 strain showed a superior performance since it was the most efficient in reducing disease incidence in wheat explants by 64.5%, in addition to having the strongest plant growth promotion activity under salt stress. Both in vitro and in vivo assays showed that MA9, MA14, MA17, and MA19 strains were able to play significant PGPB roles. However, biopriming with Bacillus subtilis MA17 offered the highest plant growth promotion and salinity tolerance, and bioprotection against FHB. Hence, it would be worth testing the MA17 strain under field conditions as a step towards its commercial production. Moreover, the strain could be further assessed for its plausible role in bioprotection and growth promotion in other crop plants. Thus, it was believed that the strain has the potential to significantly contribute to wheat production in arid and semi-arid regions, especially the salt-affected Middle Eastern Region, in addition to its potential role in improving wheat production under biotic and abiotic stresses in other parts of the world.