Phenogenetic profile and agronomic contribution of Azospirillum argentinense Az39T, a reference strain for the South American inoculant industry.

Azospirillum sp. is a plant growth-promoting rhizobacteria largely recognized for its potential to increase the yield of different important crops. In this work, we present a thorough genomic and phenotypic analysis of A. argentinense Az39T to provide new insights into the beneficial mechanisms of this microorganism. Phenotypic analyses revealed the following in vitro abilities: growth at 20-38 °C (optimum, 28 °C), pH 6.0-8.0 (optimum, pH 6.8), and in the presence of 1% (w/v) NaCl; production of variable amounts of PHB as intracellular granules; nitrogen fixation under microaerophilic conditions; IAA synthesis in the presence of L-tryptophan. Through biochemical (API 20NE) and carbon utilization profiling (Biolog) assays, we proved that A. argentinense Az39T is able to use 15 substrates and metabolize 19 different carbon substrates. Lipid composition indicated a predominance of medium and long-chain saturated fatty acids. A total of 6 replicons classified as one main chromosome, three chromids, and two plasmids, according to their tRNA and core essential genes contents, were identified. Az39T genome includes genes associated with multiple plant growth-promoting (PGP) traits such as nitrogen fixation and production of auxins, cytokinin, abscisic acid, ethylene, and polyamines. In addition, Az39T genome harbor genetic elements associated with physiological features that facilitate its survival in the soil and competence for rhizospheric colonization; this includes motility, secretion system, and quorum sensing genetic determinants. A metadata analysis of Az39T agronomic performance in the pampas region, Argentina, demonstrated significant grain yield increases in wheat and maize, proving its potential to provide better growth conditions for dryland cereals. In conclusion, our data provide a detailed insight into the metabolic profile of A. argentinense Az39T, the strain most widely used to formulate non-legume inoculants in Argentina, and allow a better understanding of the mechanisms behind its field performance.

The drop plate method as an alternative for Azospirillum spp. viable cell enumeration within the consensus protocol of the REDCAI network.

Quality evaluation of commercial inoculants is essential to warrant an adequate crop response to inoculation within a biosecurity framework. In this sense, this work is aimed at standardizing and validating the drop plate method for the enumeration of Azospirillum viable cells as an alternative to the spread plate technique, which is currently proposed in the consensus protocol of the REDCAI network. Between 14 and 25 private and public laboratories participated in three independent trials. We obtained consistent and robust results that allowed to confirm that both techniques are equivalent, concluding that the drop plate method is an alternative enumeration technique that is adequate to be included in the abovementioned consensus protocol.

Towards sustainable yield improvement: field inoculation of soybean with Bradyrhizobium and co-inoculation with Azospirillum in Mozambique.

The effects of sole inoculation of soybean (Glycine max L. Merrill) with Bradyrhizobium and co-inoculation with Bradyrhizobium and Azospirillum on nodulation, plant growth and yields were investigated in the 2013/2014 and 2014/2015 cropping seasons under field conditions in Mozambique. The treatments included (1) Control (non-inoculated control, with symbiosis depending on indigenous rhizobia), (2) Urea (non-inoculated, receiving 200 kg ha-1 of N), (3) Sole inoculation with B. diazoefficiens strain USDA 110, and (4) Co-inoculation with B. diazoefficiens strain USDA 110 and A. brasilense strains Ab-V5 and Ab-V6, evaluated in a randomized complete block design with five replications. Nodule number and dry weight, shoot dry weight, biological and grain yields, grain dry weight, and harvest index were evaluated. In general, both sole inoculation and co-inoculation enhanced nodulation in relation to control. Sole inoculation increased grain yield by 22% (356 kg ha-1), the same enhancement magnitude attained under mineral N treatment, suggesting that Bradyrhizobium inoculation provides ecological and economic sustainability to the soybean crop in Mozambique or other countries with similar agro-climatic conditions. Co-inoculation did not increase grain yields in relation to neither the control nor sole inoculation, indicating that further research with adapted and high yielding soybean varieties along with effective rhizobial strains is required in Mozambique to attune the beneficial Azospirillum-plant cultivar-rhizobia interactions that have been reported in other countries for several legumes, including soybean.

Potentially Mobile Denitrification Genes Identified in Azospirillum sp. Strain TSH58.

Denitrification ability is sporadically distributed among diverse bacteria, archaea, and fungi. In addition, disagreement has been found between denitrification gene phylogenies and the 16S rRNA gene phylogeny. These facts have suggested potential occurrences of horizontal gene transfer (HGT) for the denitrification genes. However, evidence of HGT has not been clearly presented thus far. In this study, we identified the sequences and the localization of the nitrite reductase genes in the genomes of 41 denitrifying Azospirillum sp. strains and searched for mobile genetic elements that contain denitrification genes. All Azospirillum sp. strains examined in this study possessed multiple replicons (4 to 11 replicons), with their sizes ranging from 7 to 1,031 kbp. Among those, the nitrite reductase gene nirK was located on large replicons (549 to 941 kbp). Genome sequencing showed that Azospirillum strains that had similar nirK sequences also shared similar nir-nor gene arrangements, especially between the TSH58, Sp7T, and Sp245 strains. In addition to the high similarity between nir-nor gene clusters among the three Azospirillum strains, a composite transposon structure was identified in the genome of strain TSH58, which contains the nir-nor gene cluster and the novel IS6 family insertion sequences (ISAz581 and ISAz582). The nirK gene within the composite transposon system was actively transcribed under denitrification-inducing conditions. Although not experimentally verified in this study, the composite transposon system containing the nir-nor gene cluster could be transferred to other cells if it is moved to a prophage region and the phage becomes activated and released outside the cells. Taken together, strain TSH58 most likely acquired its denitrification ability by HGT from closely related Azospirillum sp. denitrifiers.IMPORTANCE The evolutionary history of denitrification is complex. While the occurrence of horizontal gene transfer has been suggested for denitrification genes, most studies report circumstantial evidences, such as disagreement between denitrification gene phylogenies and the 16S rRNA gene phylogeny. Based on the comparative genome analyses of Azospirillum sp. denitrifiers, we identified denitrification genes, including nirK and norCBQD, located on a mobile genetic element in the genome of Azospirillum sp. strain TSH58. The nirK was actively transcribed under denitrification-inducing conditions. Since this gene was the sole nitrite reductase gene in strain TSH58, this strain most likely benefitted by acquiring denitrification genes via horizontal gene transfer. This finding will significantly advance our scientific knowledge regarding the ecology and evolution of denitrification.

Effects of Different Sources of Nitrogen on Endophytic Colonization of Rice Plants by Azospirillum sp. B510.

Azospirillum sp. B510, a free-living nitrogen-fixing bacterium isolated from the stems of rice (Oryza sativa cv. Nipponbare), was investigated to establish effective conditions for the colonization of rice plants. We analyzed the effects of the nitrogen sources KNO3, NH4Cl, urea (CO[NH2]2), and NH4NO3 at different concentrations (0.01-10 mM) on this colonization. Nitrogen promoted plant growth in a concentration-dependent manner, with minor differences being observed among the different nitrogen sources. Bacterial colonization was markedly suppressed on media containing NH4+ concentrations higher than 1 mM. Since concentrations of up to and including 10 mM NH4+ did not exhibit any antibacterial activity, we analyzed several factors affecting the NH4+-dependent inhibition of endophytic colonization, including the accumulation of the reactive oxygen species H2O2 and the secretion of the chemotactic substrate malic acid. The accumulation of H2O2 was increased in rice roots grown on 1 mM NH4Cl. The amounts of malic acid secreted from NH4-grown rice plants were lower than those secreted from plants grown without nitrogen or with KNO3. Although the bacterium exhibited chemotactic activity, moving towards root exudates from plants grown without nitrogen and KNO3-grown plants, this activity was not observed with root exudates from NH4+-grown plants. NH4+, but not NO3-, caused the acidification of growth media, which inhibited plant bacterial colonization. These NH4+-dependent phenomena were markedly suppressed by the stabilization of medium pH using a buffer. These results demonstrate that the type and concentration of nitrogen fertilizer affects the colonization of rice plants by Azospirillum sp. B510.

Effects of colonization of a bacterial endophyte, Azospirillum sp. B510, on disease resistance in tomato.

A plant growth-promoting bacteria, Azospirillum sp. B510, isolated from rice, can enhance growth and yield and induce disease resistance against various types of diseases in rice. Because little is known about the interaction between other plant species and this strain, we have investigated the effect of its colonization on disease resistance in tomato plants. Treatment with this strain by soil-drenching method established endophytic colonization in root tissues in tomato plant. The endophytic colonization with this strain-induced disease resistance in tomato plant against bacterial leaf spot caused by Pseudomonas syringae pv. tomato and gray mold caused by Botrytis cinerea. In Azospirillum-treated plants, neither the accumulation of SA nor the expression of defense-related genes was observed. These indicate that endophytic colonization with Azospirillum sp. B510 is able to activate the innate immune system also in tomato, which does not seem to be systemic acquired resistance.

In vitro PGPR properties and osmotic tolerance of different Azospirillum native strains and their effects on growth of maize under drought stress.

Osmotic variations in the soil can affect bacterial growth diminishing the number of inoculated bacteria. In a scenario of water deficit having tolerant bacteria would be beneficial to achieve a better response of the plant to stress. Thus, selection of more resistant bacteria could be useful to design new inoculants to be used in arid zones. In this sense, a group of Azospirillum isolates deposited in INTA collection was characterized in order to select strains tolerant to osmotic stress. The results obtained demonstrated that Az19 strain has similar in vitro PGPR characteristics to Az39, the most used strain in Argentina for inoculants industries, with the advantage of a better tolerance to osmotic and salt stress. Inoculation of maize plants with this strain resulted in a better response against water deficit compared to Az39 strain, encouraging us to further study the behavior of this strain in greenhouse and field trials in view of developing new inoculants suitable for areas with water deficit.

Activation of a calcium-dependent protein kinase involved in the Azospirillum growth promotion in rice.

Rice seedlings (Oryza sativa) inoculated with the plant growth-promoting rhizobacteria Azospirillum brasilense FT326 showed an enhanced development of the root system 3 days after inoculation. Later on, a remarkable enlargement of shoots was also evident. An increase in the Ca2+-dependent histone kinase activity was also detected as a result of inoculation. The biochemical characterization and Western-blot analysis of the kinase strongly supports the hypothesis that it belongs to a member of the rice CDPK family. The fact that the amount of the protein did not change upon inoculation seems to indicate that a posttranslational activation is responsible for the change in the enzymatic activity. An in-gel kinase experiment identified a 46 kDa CDPK like protein kinase as a putative component of the signal transduction pathway triggered by Azospirillum inoculation. To our knowledge, this is the first report on the possible involvement of a Ca2+-dependent protein kinase in promotion of rice plants growth by A. brasilense.

Isolation and identification by 16S rRNA sequence analysis of plant growth-promoting azospirilla from the rhizosphere of wheat

ABSTRACT The main objective of the present study was to isolate phytohormone-producing, phosphate-solubilizing strains of Azospirillum from wheat to be used as inoculants for plant growth promotion. Five Azospirillum strains were isolated from the rhizosphere of field-grown wheat (Triticum aestivum L.), and it was confirmed by BOX-polymerase chain reaction (PCR) that the isolates were different and not re-isolates of the same strain. Sequence analysis of the PCR-amplified 16S rRNA gene indicated that four isolates showed maximum similarity to Azospirillum brasilense and one isolate showed maximum similarity to Azospirillum zeae. This is the first report indicating the presence of an A. zeae like isolate in the wheat rhizosphere in Pakistan. The bacterial isolates were characterized for their plant growth-promoting traits, phosphate solubilization, and indole-3-acetic acid (IAA) production. None of the isolates showed phosphate solubilization activity in the commonly used Pikovskaya medium. However, all strains (except AzoK4) exhibited ability to solubilize tricalcium phosphate (TCP) in modified Pikovskaya medium in which sucrose was replaced by Na-malate, as well as in TCP-supplemented Luria-Bertani (LB) medium. Organic acids, such as acetic, citric, lactic, malic, and succinic acids, were detected in culture supernatants of the tested Azospirillum strains. All strains exhibited ability to produce IAA in the growth medium, except Azospirillum sp. AzoK1. Among the strains tested, the maximum IAA production (30.49 ± 1.04 mg L-1) and phosphate solubilization (105.50 ± 4.93 mg L-1) were shown by a pure culture of Azospirillum sp. AzoK2. In pot experiments, single-strain inocula of Azospirillum sp. AzoK1 and AzoK2 improved wheat plant growth.

Isolation and identification by 16S rRNA sequence analysis of plant growth-promoting azospirilla from the rhizosphere of wheat.

The main objective of the present study was to isolate phytohormone-producing, phosphate-solubilizing strains of Azospirillum from wheat to be used as inoculants for plant growth promotion. Five Azospirillum strains were isolated from the rhizosphere of field-grown wheat (Triticum aestivum L.), and it was confirmed by BOX-polymerase chain reaction (PCR) that the isolates were different and not re-isolates of the same strain. Sequence analysis of the PCR-amplified 16S rRNA gene indicated that four isolates showed maximum similarity to Azospirillum brasilense and one isolate showed maximum similarity to Azospirillum zeae. This is the first report indicating the presence of an A. zeae like isolate in the wheat rhizosphere in Pakistan. The bacterial isolates were characterized for their plant growth-promoting traits, phosphate solubilization, and indole-3-acetic acid (IAA) production. None of the isolates showed phosphate solubilization activity in the commonly used Pikovskaya medium. However, all strains (except AzoK4) exhibited ability to solubilize tricalcium phosphate (TCP) in modified Pikovskaya medium in which sucrose was replaced by Na-malate, as well as in TCP-supplemented Luria-Bertani (LB) medium. Organic acids, such as acetic, citric, lactic, malic, and succinic acids, were detected in culture supernatants of the tested Azospirillum strains. All strains exhibited ability to produce IAA in the growth medium, except Azospirillum sp. AzoK1. Among the strains tested, the maximum IAA production (30.49±1.04mgL(-1)) and phosphate solubilization (105.50±4.93mgL(-1)) were shown by a pure culture of Azospirillum sp. AzoK2. In pot experiments, single-strain inocula of Azospirillum sp. AzoK1 and AzoK2 improved wheat plant growth.

Cultivation-Based and Molecular Assessment of Bacterial Diversity in the Rhizosheath of Wheat under Different Crop Rotations.

A field study was conducted to compare the formationand bacterial communities of rhizosheaths of wheat grown under wheat-cotton and wheat-rice rotation and to study the effects of bacterial inoculation on plant growth. Inoculation of Azospirillum sp. WS-1 and Bacillus sp. T-34 to wheat plants increased root length, root and shoot dry weight and dry weight of rhizosheathsoil when compared to non-inoculated control plants, and under both crop rotations. Comparing both crop rotations, root length, root and shoot dry weight and dry weight of soil attached with roots were higher under wheat-cotton rotation. Organic acids (citric acid, malic acid, acetic acid and oxalic acid) were detected in rhizosheaths from both rotations, with malic acid being most abundant with 24.8±2 and 21.3±1.5 µg g(-1) dry soil in wheat-cotton and wheat-rice rotation, respectively. Two sugars (sucrose, glucose) were detected in wheat rhizosheath under both rotations, with highest concentrations of sucrose (4.08±0.5 µg g(-1) and 7.36±1.0 µg g(-1)) and glucose (3.12±0.5 µg g(-1) and 3.01± µg g(-1)) being detected in rhizosheaths of non-inoculated control plants under both rotations. Diversity of rhizosheath-associated bacteria was evaluated by cultivation, as well as by 454-pyrosequencing of PCR-tagged 16S rRNA gene amplicons. A total of 14 and 12 bacterial isolates predominantly belonging to the genera Arthrobacter, Azospirillum, Bacillus, Enterobacter and Pseudomonaswere obtained from the rhizosheath of wheat grown under wheat-cotton and wheat-rice rotation, respectively. Analysis of pyrosequencing data revealed Proteobacteria, Bacteriodetes and Verrucomicrobia as the most abundant phyla in wheat-rice rotation, whereas Actinobacteria, Firmicutes, Chloroflexi, Acidobacteria, Planctomycetes and Cyanobacteria were predominant in wheat-cotton rotation. From a total of 46,971 sequences, 10.9% showed ≥97% similarity with 16S rRNA genes of 32 genera previously shown to include isolates with plant growth promoting activity (nitrogen fixation, phosphate-solubilization, IAA production). Among these, the most predominant genera were Arthrobacter, Azoarcus, Azospirillum, Bacillus, Cyanobacterium, Paenibacillus, Pseudomonas and Rhizobium.

Evaluation of the possibility to use the plant-microbe interaction to stimulate radioactive 137Cs accumulation by plants in a contaminated farm field in Fukushima, Japan.

Field experiments in a contaminated farmland in Nihonmatsu city, Fukushima were conducted to assess the effectiveness of the plant-microbe interaction on removal of radiocesium. Before plowing, 93.3% of radiocesium was found in the top 5 cm layer (5,718 Bq kg DW(-1)). After plowing, Cs radioactivity in the 0-15 cm layer ranged from 2,037 to 3,277 Bq kg DW(-1). Based on sequential extraction, the percentage of available radiocesium (water soluble + exchangeable) was fewer than 10% of the total radioactive Cs. The transfer of (137)Cs was investigated in three agricultural crops; komatsuna (four cultivars), Indian mustard and buckwheat, inoculated with a Bacillus or an Azospirillum strains. Except for komatsuna Nikko and Indian mustard, inoculation with both strains resulted in an increase of biomass production by the tested plants. The highest (137)Cs radioactivity concentration in above-ground parts was found in Bacillus-inoculated komatsuna Nikko (121 Bq kg DW(-1)), accompanied with the highest (137)Cs TF (0.092). Furthermore, komatsuna Nikko-Bacillus and Indian mustard-Azospirillum associations gave the highest (137)Cs removal, 131.5 and 113.8 Bq m(-2), respectively. Despite the beneficial effect of inoculation, concentrations of (137)Cs and its transfer to the tested plants were not very high; consequently, removal of (137)Cs from soil would be very slow.

Stable cesium uptake and accumulation capacities of five plant species as influenced by bacterial inoculation and cesium distribution in the soil.

The effects of inoculation with Bacillus and Azospirillum strains on growth and cesium accumulation of five plant species, Komatsuna, Amaranth, sorghum, common millet and buckwheat, grown on cesium-spiked soil were assessed for potential use in cesium remediation. Pot experiments were performed using "artificially" Cs-contaminated soil. Three treatments were applied based on Cs location in the soil. For a soil height of 15 cm in the pots, Cs was added as follows: in the top five cm to imitate no ploughing condition; in the bottom five cm simulating inverted ploughing; and uniformly distributed Cs reproducing normal plowing. Generally, inoculation of Cs-exposed plants significantly enhanced growth and tolerance to this element. Transfer factor (ratio of Cs concentration in the plant tissues to that in surrounding soil) was strongly influenced by Cs distribution, with higher values in the top-Cs treatment. Within this treatment, inoculation of Komatsuna with Bacillus and Azospirillum strains resulted in the greatest transfer factors of 6.55 and 6.68, respectively. Cesium content in the shoots was high in the Azospirillum-inoculated Komatsuna, Amaranth, and buckwheat, i.e., 1,830, 1,220, and 1,030 µg per pot, respectively (five plants were grown in each pot). Therefore, inoculation of Komatsuna and Amaranth with the strains tested here could be effective in enhancing Cs accumulation. The decrease of Cs transfer under uniform- and bottom-Cs treatments would suggest that countermeasures aiming at decreasing the transfer of Cs could rely on ploughing practices.

Phenotypic and molecular characterization of native Azospirillum strains from rice fields to improve crop productivity.

Beneficial microorganisms have been considered as an important tool for crop improvement. Native isolates of Azospirillum spp. were obtained from the rhizospheres of different rice fields. Phenotypic, biochemical and molecular characterizations of these isolates led to the identification of six efficient strain of Azospirillum. PCR amplification of the nif genes (nifH, nifD and nifK) and protein profile of Azospirillum strains revealed inter-generic and inter-specific diversity among the strains. In vitro nitrogen fixation performance and the plant growth promotion activities, viz. siderophore, HCN, salicylic acid, IAA, GA, zeatin, ABA, NH3, phosphorus metabolism, ACC deaminase and iron tolerance were found to vary among the Azospirillum strains. The effect of Azospirillum formulations on growth of rice var. Khandagiri under field condition was evaluated, which revealed that the native formulation of Azospirillum of CRRI field (As6) was most effective to elevate endogenous nutrient content, and improved growth and better yield are the result. The 16S rRNA sequence revealed novelty of native Azospirillum lipoferum (As6) (JQ796078) in the NCBI database.

Impact of Azospirillum sp. B510 inoculation on rice-associated bacterial communities in a paddy field.

Rice seedlings were inoculated with Azospirillum sp. B510 and transplanted into a paddy field. Growth in terms of tiller numbers and shoot length was significantly increased by inoculation. Principal-coordinates analysis of rice bacterial communities using the 16S rRNA gene showed no overall change from B510 inoculation. However, the abundance of Veillonellaceae and Aurantimonas significantly increased in the base and shoots, respectively, of B510-inoculated plants. The abundance of Azospirillum did not differ between B510-inoculated and uninoculated plants (0.02-0.50%). These results indicate that the application of Azospirillum sp. B510 not only enhanced rice growth, but also affected minor rice-associated bacteria.

Granulomatous infection of the hand and wrist due to Azospirillum spp.

We report a case of Azospirillum infection manifestating as granulomatous tenosynovitis of the right hand, in an immunocompetent middle-aged female. We highlight the unusual source of the infection, the diagnostic workup, as well as the treatment approach.

Comparison of prominent Azospirillum strains in Azospirillum-Pseudomonas-Glomus consortia for promotion of maize growth.

Azospirillum are prominent plant growth-promoting rhizobacteria (PGPR) extensively used as phytostimulatory crop inoculants, but only few studies are dealing with Azospirillum-containing mixed inocula involving more than two microorganisms. We compared here three prominent Azospirillum strains as part of three-component consortia including also the PGPR Pseudomonas fluorescens F113 and a mycorrhizal inoculant mix composed of three Glomus strains. Inoculant colonization of maize was assessed by quantitative PCR, transcription of auxin synthesis gene ipdC (involved in phytostimulation) in Azospirillum by RT-PCR, and effects on maize by secondary metabolic profiling and shoot biomass measurements. Results showed that phytostimulation by all the three-component consortia was comparable, despite contrasted survival of the Azospirillum strains and different secondary metabolic responses of maize to inoculation. Unexpectedly, the presence of Azospirillum in the inoculum resulted in lower phytostimulation in comparison with the Pseudomonas-Glomus two-component consortium, but this effect was transient. Azospirillum's ipdC gene was transcribed in all treatments, especially with three-component consortia, but not with all plants and samplings. Inoculation had no negative impact on the prevalence of mycorrhizal taxa in roots. In conclusion, this study brought new insights in the functioning of microbial consortia and showed that Azospirillum-Pseudomonas-Glomus three-component inoculants may be useful in environmental biotechnology for maize growth promotion.

Assessment of compost as a bio-fertilizer for the growth of paddy.

The vegetable wastes were converted into compost by a stepwise degradation and its characteristics were studied and analysed at each stage. The temperature increased from 290C to 60 degrees C on 60th day and reached 33 degrees C on 90th day. Shift of pH from 7.6 to 7.3 on 60th day caused a shift of microflora from 12.01 x 10(7) to 11.13 x 10(8) CFU ml(-1) on 30th day and 63.2 x 10(6) on 60th day and 36.75 x 10(6) on 90th day. Shift of microflora caused high decomposition of the waste into compost which were used for enriching the soil as manures. The other characteristics such as moisture, ash content and C:N ratio established the short period required for preparing a complete compost of good quality. The study showed the efficiency of these organisms as plant growth promoting rhizobacteria. Combinations of microorganisms with compost act as a good biofertilizer which improves the fertility of soil and increases plant growth. Better results were produced by organisms in combinations like Azospirillum, Rhizobium and Azotobacter. The least growth in shoot length (64 cm) total fresh weight (151g) and total dry weight (3.994 g) were observed in paddy grown in soil and Bacillus combination, but microbial mixture of compost and soil gave high paddy growth efficiency. The present study concludes that the rhizospheric organisms play well as plant growth promoting agents and gave a better yield and growth of plants in combination with the compost.

In vitro propagation of fraser photinia using Azospirillum-mediated root development.

Fraser photinia (Photinia × fraseri Dress.) is a woody plant of high ornamental value. The traditional propagation system for photinia is by rooting apical cuttings using highly concentrated auxin treatments. However, photinia micropropagation is an effective alternative to traditional in vivo propagation which is affected by the seasonal supply of cuttings, the long time required to obtain new plants, and the difficulties in rooting some clones.A protocol for in vitro propagation of fraser photinia using the plant growth-promoting ability of some rhizobacteria is described here. Bacterial inoculation is a new tool in micropropagation protocols that improves plant development in in vitro culture. Shoots culture on a medium containing MS macro- and microelements, Gamborg's vitamins (BM), N (6)-benzyladenine (BA, 11.1 µM), and gibberellic acid (1.3 µM) produce well-established explants. Proliferation on BM medium supplemented with 4.4 µM BA results in four times the number of shoots per initial shoot that develops monthly. Consequently, there is a continuous supply of plant material since shoot production is independent of season. Azospirillum brasilense inoculation, after 49.2 µM indole-3-butyric acid pulse treatment, stimulates early rooting of photinia shoots and produces significant increase in root fresh and dry weights, root surface area, and shoot fresh and dry weights in comparison with controls. Furthermore, inoculated in vitro photinia plants show anatomical and morphological changes that might lead to better adaptation in ex vitro conditions after transplanting, compared with the control plants.