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1.
Application of plant growth-promoting rhizobacteria (PGPR) has been shown to increase legume growth and development under field and controlled environmental conditions. The present study was conducted to isolate plant growth-promoting rhizobacteria (PGPR) from the root nodules of lentil (Lens culinaris Medik.) grown in arid/semi-arid region of Punjab, Pakistan and examined their plant growth-promoting abilities. Five bacterial isolates were isolated, screened in vitro for plant growth-promoting (PGP) characteristics and their effects on the growth of lentil were assessed under in vitro, hydroponic and greenhouse (pot experiment) conditions. All the isolates were Gram negative, rod-shaped and circular in form and exhibited the plant growth-promoting attributes of phosphate solubilization and auxin (indole acetic acid, IAA) production. The IAA production capacity ranged in 0.5-11.0 μg mL-1 and P solubilization ranged in 3-16 mg L-1 . When tested for their effects on plant growth, the isolated strains had a stimulatory effect on growth, nodulation and nitrogen (N) and phosphorus (P) uptake in plants on nutrient-deficient soil. In the greenhouse pot experiment, application of PGPR significantly increased shoot length, fresh weight and dry weight by 65%, 43% and 63% and the increases in root length, fresh weight and dry weight were 74%, 54% and 92%, respectively, as compared with the uninoculated control. The relative increases in growth characteristics under in vitro and hydroponic conditions were even higher. PGPR also increased the number of pods per plant, 1 000-grain weight, dry matter yield and grain yield by 50%, 13%, 28% and 29%, respectively, over the control. The number of nodules and nodule dry mass increased by 170% and 136%, respectively. After inoculation with effective bacterial strains, the shoot, root and seed N and P contents increased, thereby increasing both N and P uptake in plants. The root elongation showed a positive correlation (R2 = 0.67) with the IAA production and seed yield exhibited a positive correlation (R2 = 0.82) with root nodulation. These indicated that the isolated PGPR rhizobial strains can be best utilized as potential agents or biofertilizers for stimulating the growth and nutrient accumulation of lentil.  相似文献   

2.
The ability of phosphate-solubilizing rhizobacteria to enhance the growth and phosphorus uptake of canola (Brassica napus L., cv. Legend) was studied in potted soil experiments in the growth chamber. One hundred and eleven bacteria isolated from the rhizosphere of field-grown plants, and a collection of nine bacteria known to be effective plant growth-promoting rhizobacteria (PGPR), were screened for P-solubilization in vitro. All rhizobacteria were identified using whole-cell fatty acids methyl ester (FAME) profiles. The best P-solubilizing isolates were two Bacillus brevis strains, B. megaterium, B. polymyxa, B. sphaericus, B. thuringiensis, and Xanthomonas maltophilia (PGPR strain R85). The P-solubilizers were tested for their effects on growth and P-uptake of canola plants in a P-deficient soil amended with rock phosphate. Although some of the P-solubilizing rhizobacteria significantly increased plant height or pod yield, none increased P-uptake. The most effective inoculant was a B. thuringiensis isolate which significantly increased the number and weight of pods and seed yield without rock phosphate. Xanthomonas maltophilia increased plant height, whereas the other bacilli increased the number on weight of pods. These results demonstrate the potential use of these P-solubilizing rhizobacteria as inoculants for canola, but indicate that P-solubilization was not the main mechanism responsible for positive growth response. Received: 8 February 1996  相似文献   

3.
Plant growth-promoting rhizobacteria (PGPR) strains CHA0 (Pseudomonas fluorescens), IE-6 S+ (Pseudomonas aeruginosa) and 569Smr (Bradyrhizobium japonicum) were tested singly and in combinations for biological control against multiple tomato pathogens (root-infecting fungi and root-knot nematodes). Strains CHA0 and IE-6S+ inhibited in vitro growth of 569Smr while IE-6S+ suppressed CHA0. The bacterial species not only inhibited the radial growth of three root-infecting fungi, Macrophomina phaseolina, Fusarium solani and Rhizoctonia solani (AG 8), but also caused substantial mortality of Meloidogyne javanica juveniles. Used as a soil drench the three bacteria not only suppressed root-infecting fungi and root-knot nematodes but also enhanced growth of tomato plants both under glasshouse and field conditions. The suppressive effect was generally more pronounced when the bacteria were employed together. Strain IE-6S+ exhibited better rhizosphere colonization than CHA0 and 569Smr. Populations of CHA0 in the rhizosphere declined when the bacterium was used with either IE-6S+ and/or 569Smr, while populations of IE-6S+ in the rhizosphere were enhanced when used in combination with CHA0 and/or 569Smr. IE-6S+ was the only bacterium that colonized inner root tissues of tomato plants. When using an iron chelator to create iron deficiency in the soil, the biocontrol efficacy of the bacteria against F. solani and R. solani was enhanced while against M. phaseolina and M. javanica this activity remained unchanged. Only strain 569Smr gave significant suppression of M. phaseolina in both iron-deficient and iron-sufficient soils.  相似文献   

4.
云南湿热地区优良牧草距瓣豆的磷钾营养   总被引：2，自引：0，他引：2  
采用单因子随机区组设计,在湿热地区赤红壤上开展优良热带豆科牧草—距瓣豆的磷、钾营养需求的试验。结果表明,施用磷、钾肥单位面积距瓣豆的干物质产量、氮磷钾总吸收量和粗蛋白产量明显提高;施磷可使距瓣豆的磷含量增加,氮含量相对稳定,钾含量逐渐下降;而且年均干物质产量和粗蛋白产量分别与施磷量存在的一元二次曲线方程的拟合程度较好（Yp＝1289+50.5X-0.55X2, r=0.9519**;Ycp＝254+12.2X1-0.14X12,r＝0.9398**）。施钾使距瓣豆的氮、磷含量趋于相对稳定,钾含量有所提高;年均干物质产量和粗蛋白产量分别与施钾量亦存在的一元二次曲线方程的拟合程度较好（Yk＝1259+19.2X-0.087X2,r=0.8546**;Ycp＝248+4.3X1-0.0204X12,r=0.8055**）。结果还表明,距瓣豆定植的第三年,必须按照磷钾比例1∶0.5～1.2施入磷、钾肥,以满足距瓣豆生长的营养需求和维持距瓣豆的高产稳产。  相似文献   

5.
Understanding the interaction mechanisms between plant growth-promoting rhizobacteria (PGPR), leguminous crops, and rhizobia is necessary to effectively use PGPR in increasing the biological nitrogen fixation of legumes. We determined the coinoculation effects of Bradyrhizobium japonicum A1017 and a gusA-marked strain of Pseudomonas fluorescens 2137, P. fluorescens WCS365, Azomonas agilis 125, and Azospirillum lipoferum 137 on soybean [Glycine max (L.) Merr] cv. Enrei grown under axenic conditions. The gusA-marked rhizobacteria effectively colonized the root tips and surfaces near the roots tips with a colonization rate ranging from 7.50 to 8.62 log colony forming units (cfu) gfw-1. P. fluorescens 2137 had the highest colonization activity on soybean roots whether inoculated alone or coinoculated with B. japonicum A1017. Coinoculation of P. fluorescens 2137 and B. japonicum A1017 increased the colonization of B. japonicum A1017 on soybean roots, nodule number, and acetylene reduction activity (ARA) at 10 and 20 days after inoculation. Moreover, the addition of sterile spent medium of P. fluorescens 2137 increased the growth of B. japonicum A1017 in yeast mannitol broth (YMB), indicating that P. fluorescens 2137 may have released substances that increased the rhizobial population. The results of this study suggest that the enhanced nodulation and ARA of soybean due to the high colonization of P. fluorescens on soybean roots could depend on the production of growth-promoting substances that stimulate the growth of B. japonicum. However, coinoculation with P. fluorescens WCS365 decreased the nodule number and ARA, despite its slight stimulation of the growth of B. japonicum on the roots, indicating that coinoculation effects are strain dependent.  相似文献   

6.
Improvement in sustainable production of switchgrass (SG, Panicum virgatum L), as a purpose-grown biomass feedstock crop, could be realized through investigation of plant–microbe interactions associated with plant growth promoting rhizobacteria (PGPR), capable of biological nitrogen fixation (BNF). The objective of this study is to increase establishment year production of SG biofuels by inoculation with a mixed PGPR inoculum. We isolated pure strains of N2-fixing, and other PGPR, from SG rhizomes. The bacteria were identified as Paenibacillus polymyxa, an N2-fixing bacterium, and other PGPR capable of solubilizing phosphate and/or producing auxins. Field trials utilizing these strains in a mixed PGPR inoculum showed that inoculated plants contained more N in tillers during anthesis but not at senescence, suggesting that more N could be cycled to belowground roots and rhizomes for winter storage. The amount of N removal in biomass and recovery of fertilizer N were also greater for inoculated than uninoculated plants. PGPR inoculation also resulted in positive N balances, suggesting improved access to N from non-fertilizer N sources, possibly through BNF and improved soil N uptake. Overall, inoculation of SG with PGPR enhanced N acquisition and could be an effective strategy to increase the establishment year production of this crop.  相似文献   

7.
Enhancement of plant growth by Bacillus is well documented and several mechanisms have been suggested for the phytostimulatory activity of this group of plant growth-promoting rhizobacteria (PGPR). In the present work, the PGP potential of plant associated Bacillus spp. and their growth-promoting effect on wheat were studied. Six out of 35 strains were chosen based on seed germination assay, plant growth-promoting abilities, enzymatic function, and auxin production. All tested strains were subjected to pot experiments and their phenotypic and molecular assays were also done. Two Bacillus strains including WhIr-15 and WhIr-12 produce maximum amount of auxin (16.2 and 14 µg ml?1, respectively). Strain WhIr-15 had just the ability to produce indo-3-acetic acid (IAA), lipase, and protease enzymes. Strain WhIr-12 was also recorded positive for siderophore, auxin production, and phosphorus (P) solubilization. Bacterial IAA production positively correlated with root length (r = 0.875; p ≤ 0.05). Significant enhancement in root weight (71% and 53%) and in panicle weight (91% and 77%) was recorded in WhIr-15 and WhIr-12, respectively, over untreated controls. Based on phenotypic and 16S rDNA sequencing, these two strains belong to Bacillus sp. Based on our results, phytohormone-producing Bacillus sp. can be applied at field level to improve wheat productivity.  相似文献   

8.
The present study was conducted to work out the conjoint application of indigenous PGPR (plant growth promoting rhizobacteria) and chemical fertilizers levels on the productivity of maize (Zea mays L.). Three best PGPR isolates (B1N1, MAT1 and DHK) having maximum PGP (plant growth promoting) traits were screened at different recommended doses (80%, 60% and 40%) of NP (Nitrogen and Phosphorous) under net house conditions, and finally two isolates (B1N1 and MAT1) along with optimum dose i.e. 80% of NP were selected for field experimentation, which was performed for two years consecutively i.e. 2013–2015 under random block design (RBD). Conjoint application of 80% recommended doses of NP with PGPR (B1N1) significantly increased maize yield (11.7%), plant height (12.9%) and biomass (17.9%), over control (100% recommend dose of fertilizer (RDF) of chemical fertilizer). Therefore, the results revealed the potential of indigenous PGPR isolates to supplement about 20% NP fertilizers without hampering the productivity of maize.  相似文献   

9.
Strains isolated from chickpea (Cicer arietinum L.) rhizospheric soil from selected sites in Algeria were screened for their plant-growth-promoting potential, for indole acetic acid production and P solubilization ability. Then, we selected native rhizobial strains with high nitrogen-fixing potential. On the basis of their efficiency under controlled conditions, two plant-growth-promoting rhizobacteria (PGPR) isolates and three nodulating bacteria were selected. Then, the effect of single PGPR isolates inoculation was compared to their combination with rhizobial inoculants on plant growth, on native cereal-growing soils under greenhouse conditions. No effects were observed on chickpea yield by using rhizobial inoculation alone, nor by PGPR-rhizobial co-inoculation on two soils presenting weak and no nodulation pattern in natural conditions. Only PGPR inoculation improved growth of plants on soil with no nodulation pattern. These findings emphasized inoculation on native soils at a little scale before large assays on field because no one could predict inocula behavior with native soil microflora.  相似文献   

10.
Inorganic fertilizers alone cannot sustain high levels of productivity. This study was conducted to determine whether higher productivity of capsicum could be achieved by conjoint application of chemical fertilizers and plant growth promoting rhizobacteria (PGPR). Four PGPR isolates (RS2, RS3, RS4, and RS7) from capsicum roots and rhizosphere were evaluated at Solan, Himachal Pradesh (India), during 2009–2012. Two best performers: RS2 and RS7 were tried singly or in consortium with different levels of chemical fertilizers under field conditions, Randomized Block Design, replicated thrice. The conjoint use of 100% recommended nitrogen, phosphorus, and potassium (NPK) doses through chemical fertilizers (RDF) plus PGPR significantly increased fruit yield, plant height, and biomass by 37%, 20%, and 30%, respectively, over sole application of 100% RDF (control). Further, response of capsicum to 80% RDF plus PGPR was statistically comparable with control. The results, therefore, indicate the potential of isolated PGPR strains to substitute about 20% NP fertilizers besides enhanced productivity of capsicum.  相似文献   

11.
长期施肥黑土微生物区系及功能多样性的变化   总被引：9，自引：0，他引：9  
Black soil （Mollisol） is one of the main soil types in northeastern China. Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis （PCR-DGGE） methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin, Heilongjiang Province. Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer＋manure treatments. The metabolic ability of the bacterial community in the manure treatment was similar to the control. DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments, suggesting that microorganisms with those bands were stable and not influenced by fertilization. However, chemical fertilizer increased the diversity of soil bacterial community. Principal com- ponent analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments, suggesting that the application of manure increased the soil microbial population, but had no effect on the bacterial community structure. Catabolic function was similar in the chemical fertilizer and chemical fertilizer＋manure treatments, but the composition structure of the soil microbes differed between them. The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.  相似文献   

12.
Soil microorganisms with phytase- and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activities are widely studied as plant growth-promoting rhizobacteria (PGPR). Here, we explored the bacterial community structure and occurrence of putative PGPR in plants grown in agro-ecosystems and undisturbed ecosystems from northern, central, and southern Chile. Total rhizobacterial community structure was evaluated by denaturing gradient gel electrophoresis, and dominant bands present in diverse ecosystems were sequenced. Significant differences in total bacterial communities were shown with some bacterial orders (Enterobacteriales, Actinomycetales, and Rhizobiales) being highly similar to both ecosystems. Twenty-nine putative PGPR, showing phytate- and ACC-degrading activities and production of auxin, were selected from across the sites. Based on 16S rRNA gene sequencing, the putative PGPR were characterized as Enterobacteriales (Enterobacter, Serratia, Pantoea, Rahnella, Leclercia), Pseudomonas, and Bacillus, consistent with previously reported PGPR and endophytic bacteria. Beta-propeller phytase genes with similarity to Bacillus were also identified. PGPR from agro-ecosystems appeared to show higher auxin production compared to those from undisturbed ecosystems. This study demonstrates that putative PGPR are widely distributed across Chilean soils. Further understanding of their contribution to the growth and adaptation of plant hosts to local soil conditions may provide opportunity for development of new PGPR in Chilean agriculture.  相似文献   

13.
Experiments were conducted in 2009–2010 at the Agricultural and Natural Resources Research Center of Yazd, Iran, to study the effect of nitrogen levels and plant growth-promoting rhizobacteria (PGPR) containing Azotobacter sp. and Azospirillum sp. on seed yield, its components and quality traits of sesame cultivars. Treatments were arranged in a factorial experiment based on randomized complete block design with nitrogen rates (0 (control), 25 and 50 kg N ha?1), cultivars (Darab-14, GL-13 and local) and N-fixing bacteria levels (non-inoculation and inoculation) were applied with three replications. Nitrogen fertilizer significantly increased yield and yield components, but reduced oil content in 2010. Inoculating seeds with PGPR increased yield and yield components of sesame cultivars compared to the control treatment. Seed yield in PGPR inoculation with half a rate of N fertilizer treatment was more than seed yield in the full rate of N fertilizer without a PGPR inoculation treatment. N fertilizer and PGPR application significantly decreased saturated fatty acids (palmitic and stearic acid) while it significantly increased unsaturated fatty acids (oleic and linoleic acid). Oleic acid had a significant negative correlation with linoleic acid (r = ?0.79). The result showed that an application of PGPR could be usefully applied to reduce use of chemical fertilizer.  相似文献   

14.
Plant growth-promoting rhizobacteria (PGPR) are considered to have a beneficial effect on host plants and may facilitate plant growth by different mechanisms. In this work, the influence of different soil types on the bacterial diversity and the stimulatory effects of selected PGPR on two cultivars of maize were investigated. A set of 292 strains was isolated from the roots and rhizosphere soil of maize cultivated in five different areas of the Rio Grande do Sul State in Brazil. 16S rDNA-PCR-RFLP and 16S rDNA partial sequencing were used for identification, and the Shannon–Weaver index was used to evaluate bacterial diversity. We evaluated the ability of each isolate to produce indole acetic acid (IAA), siderophores and solubilize phosphates. On the basis of multiple PGP traits, six isolates were selected to test their potential as plant growth-promoting rhizobacteria on maize plants. In both the roots and the rhizospheric soil of maize, the dominant bacterial genera identified were Klebsiella and Burkholderia. IAA producers were distributed widely among isolates, regardless of the sampling site. Approximately 42% of the isolates exhibited at least two attributes, and 24% showed all three PGP traits. Three strains, identified as Achromobacter, Burkholderia, and Arthrobacter, were effective as PGPR in both of the cultivars evaluated.  相似文献   

15.
Bacteria containing ACC-deaminase in the vicinity of roots may influence plant growth by modifying root architecture through their potential to regulate ethylene synthesis in plant roots. Approximately 138 isolates capable of utilizing ACC as the sole source of N were isolated from the rhizosphere soil of chickpea (Cicer arietinum L.) plants. Under axenic conditions, some rhizobacterial isolates were highly effective in increasing root length (up to 2.08 fold), number (up to 3.7 fold) and length (up to 3.9 fold) of lateral roots, and root biomass (up to 83%) of chickpea as compared to uninoculated control. Serratia proteamaculans strain J119 was found to be the most effective plant growth promoting rhizobacterium (PGPR) in improving root and shoot growth, nodulation and grain yield of chickpea as compared to respective controls in growth pouches, pot and field trials. A highly significant direct correlation (r = 0.99) was observed between number of lateral roots under axenic conditions (jar trial) and number of nodules per plant in pot and field trials. Interestingly, S. proteamaculans J119 also exhibited highest ACC-deaminase activity in addition to root colonization compared to other tested strains. The results of this study demonstrated that changes in root growth and architecture (particularly lateral roots) as a result of inoculation with PGPR containing ACC-deaminase are crucial for improving growth, yield and nodulation of chickpea under field conditions.  相似文献   

16.
Rice, one of the most important staple food crops of the world, suffers a major setback nutritionally, because it is deficient in bioavailable zinc. In an attempt to answer this problem a field study was performed for two years during 2010 and 2011. Rice plants were treated with selected plant growth promoting rhizobacteria (PGPR; P. putida, P. fluorescens, A. lipoferum, B 15, B 17, B 19, BN 17, and BN 30) and plant growth, zinc (Zn) content in different plant parts and grains was analyzed. The data obtained showed enhancement in rice growth and hence, increased rice yield in response to PGPR application. All isolates resulted in almost 1.5- to 2-fold increase in Zn content in roots, shoots as well as grains in comparison to the control. The bacterial isolates B 17, B 19, and BN 17 were of particular interest as they induced the movement of Zn from roots to shoots as well as from husk to the grains, thus making grains enriched in Zn (around 25% higher Zn content). Therefore, it can be concluded that application of PGPR strains is an important strategy to combat the problem of zinc deficiency in rice and consecutively in human masses.  相似文献   

17.
盐条件下产胞外多糖植物促生细菌研究   总被引：3，自引：0，他引：3  
Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can play an important role in alleviating soil salinity stress during plant growth and bacterial exopolysaccharide (EPS) can also help to mitigate salinity stress by reducing the content of Na + available for plant uptake.In this study,native bacterial strains of wheat rhizosphere in soils of Varanasi,India,were screened to identify the EPS-producing salt-tolerant rhizobacteria with plant growth-promoting traits.The various rhizobacteria strains were isolated and identified using 16S rDNA sequencing.The plant growth-promoting effect of inoculation of seedlings with these bacterial strains was evaluated under soil salinity conditions in a pot experiment.Eleven bacterial strains which initially showed tolerance up to 80 g L -1 NaCl also exhibited an EPS-producing potential.The results suggested that the isolated bacterial strains demonstrated some of the plant growth-promoting traits such as phosphate solubilizing ability and production of auxin,proline,reducing sugars,and total soluble sugars.Furthermore,the inoculated wheat plants had an increased biomass compared to the un-inoculated plants.  相似文献   

18.
To identify the key soil parameters influencing N2O emission from the wheat-growing season, an outdoor pot experiment with a total of 18 fertilized Chinese soils planted with wheat was conducted in Nanjing, China during the 2000/2001 wheat-growing season. Average seasonal N2O-N emission for all 18 soils was 610 mg m-2, ranging from 193 to 1,204 mg m-2, approximately a 6.2-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal N2O emission was negatively correlated with soil organic C (r2=0.5567, P<0.001), soil total N (r2=0.4684, P<0.01) and the C:N ratio (r2=0.4530, P<0.01), respectively. A positive dependence of N2O emission on the soil pH (r2=0.3525, P<0.01) was also observed. No clear relationships existed between N2O emission and soil texture, soil trace elements of Fe, Cu and Mg, and above-ground biomass of the wheat crop at harvest. A further investigation suggested that the seasonal N2O-N emission (E, mg m-2) can be quantitatively explained by E=1005-34.2SOC+4.1Sa (R2=0.7703, n=18, P=0.0000). SOC and Sa represent the soil organic C (g kg-1) and available S (mg kg-1), respectively.  相似文献   

19.
Nitrogen fixation in biological soil crusts from southeast Utah,USA   总被引：20，自引：0，他引：20  
Biological soil crusts can be the dominant source of N for arid land ecosystems. We measured potential N fixation rates biweekly for 2 years, using three types of soil crusts: (1) crusts whose directly counted cells were >98% Microcoleus vaginatus (light crusts); (2) crusts dominated by M. vaginatus, but with 20% or more of the directly counted cells represented by Nostoc commune and Scytonema myochrous (dark crusts); and (3) the soil lichen Collema sp. At all observation times, Collema had higher nitrogenase activity (NA) than dark crusts, which had higher NA than light crusts, indicating that species composition is critical when estimating N inputs. In addition, all three types of crusts generally responded in a similar fashion to climate conditions. Without precipitation within a week of collection, no NA was recorded, regardless of other conditions being favorable. Low (<1°C) and high (>26°C) temperatures precluded NA, even if soils were moist. If rain or snow melt had occurred 3 or less days before collection, NA levels were highly correlated with daily average temperatures of the previous 3 days (r2=0.93 for Collema crusts; r2=0.86 for dark crusts and r2=0.83 for light crusts) for temperatures between 1°C and 26°C. If a precipitation event followed a long dry period, NA levels were lower than if collection followed a time when soils were wet for extended periods (e.g., winter). Using a combination of data from a recording weather datalogger, time-domain reflectometry, manual dry-down curves, and N fixation rates at different temperatures, annual N input from the different crust types was estimated. Annual N input from dark crusts found at relatively undisturbed sites was estimated at 9 kg ha-1 year-1. With 20% cover of the N-fixing soil lichen Collema, inputs are estimated at 13 kg ha-1 year-1. N input from light crusts, generally indicating soil surface disturbance, was estimated at 1.4 kg ha-1 year-1. The rates in light crusts are expected to be highly variable, as disturbance history will determine cyanobacterial biomass and therefore N fixation rates.  相似文献   

20.
Phytoremediation is an emerging technology that uses plants and their associated microbes to clean up pollutants from the soil, water, and air. In order to select the plant growth-promoting rhizobacteria(PGPR) for phytoremediation of heavy metal contamination, 60 bacterial strains were isolated from the rhizosphere of two endemic plants, Prosopis laevigata and Spharealcea angustifolia, in a heavy metal-contaminated zone in Mexico. These rhizobacterial strains were characterized for the growth at different pH and salinity, extracellular enzyme production, solubilization of phosphate, heavy metal resistance, and plant growth-promoting(PGP) traits, including production of siderophores and indol-3-acetic acid(IAA). Overall, the obtained rhizobacteria presented multiple PGP traits. These rhizobacteria were also resistant to high levels of heavy metals(including As as a metalloid)(up to 480 mmol L(-1)As(V), 24 mmol L(-1)Pb(Ⅱ), 21 mmol L(-1)Cu(Ⅱ), and 4.5 mmol L(-1)Zn(Ⅱ)). Seven rhizobacterial strains with the best PGP traits were identified as members of Alcaligenes, Bacillus, Curtobacterium, and Microbacterium, and were selected for further bioassay.The inoculation of Brassica nigra seeds with Microbacterium sp. CE3R2, Microbacterium sp. NE1R5, Curtobacterium sp. NM1R1,and Microbacterium sp. NM3E9 facilitated the root development; they significantly improved the B. nigra seed germination and root growth in the presence of heavy metals such as 2.2 mmol L(-1)Zn(Ⅱ). The rhizobacterial strains isolated in the present study had the potential to be used as efficient bioinoculants in phytorremediation of soils contaminated with multiple heavy metals.  相似文献   

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