Plant-growth promoting effect of newly isolated rhizobacteria varies between two Arabidopsis ecotypes

Various rhizobacteria are known for their beneficial effects on plants, i. e. promotion of growth and induction of systemic resistance against pathogens. These bacteria are categorized as plant growth promoting rhizobacteria (PGPR) and are associated with plant roots. Knowledge of the underlying mechanisms of plant growth promotion in vivo is still very limited, but interference of bacteria with plant hormone metabolism is suggested to play a major role. To obtain new growth promoting bacteria, we started a quest for rhizobacteria that are naturally associated to Arabidopsis thaliana. A suite of native root-associated bacteria were isolated from surface-sterilized roots of the Arabidopsis ecotype Gol-1 derived from a field site near Golm (Berlin area, Germany). We found several Pseudomonas and a Microbacterium species and tested these for growth promotion effects on the Arabidopsis ecotypes Gol-1 and Col-0, and for growth-promotion associated traits, such as auxin production, ACC deaminase activity and phosphate solubilization capacity. We showed that two of the bacteria strains promote plant growth with respect to rosette diameter, stalk length and accelerate development and that the effects were greater when bacteria were applied to Col-0 compared with Gol-1. Furthermore, the capability of promoting growth was not explained by the tested metabolic properties of the bacteria, suggesting that further bacterial traits are required. The natural variation of growth effects, combined with the extensive transgenic approaches available for the model plant Arabidopsis, will build a valuable tool to augment our understanding of the molecular mechanisms involved in the natural Arabidopsis - PGPR association.     

Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis Protein Banding Patterns among Rhizobium leguminosarum biovar phaseoli Strains Isolated from the Mexican Bean Phaseolus coccineus

Several rhizobial strains were isolated from Phaseolus coccineus root nodules and were determined to be Rhizobium leguminosarum biovar phaseoli strains after reinfection of the same host plant. These strains were characterized by cultural procedures (growth on different carbon sources and intrinsic antibiotic resistance) and electrophoretic procedures (sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins). Our results showed that these rhizobia are very similar to each other, especially in their electrophoretic protein banding patterns, suggesting that they might belong to isolated populations.     

Antimicrobial activities of rhizobacterial strains of <Emphasis Type="Italic">Pseudomonas</Emphasis> and <Emphasis Type="Italic">Bacillus strains</Emphasis> isolated from rhizosphere soil of carnation (<Emphasis Type="Italic">Dianthus caryophyllus</Emphasis> cv. Sunrise)

Under the present study, an attempt was made to characterize rhizobacteria i.e. Pseudomonas and Bacillus species isolated from rhizosphere of carnation to evaluate their growth promoting effect on carnation so as to select and develop more efficient indigenous plant growth promoting and disease suppressing bioagents of specific soil type and specific plant type. Maximum strains of Pseudomonas and Bacillus sp. showed significant antimicrobial activities against most of the microorganisms tested. On the basis of in vitro antagonistic activities, the best strains were selected and used in field trial to study the influence of these strains on the growth of carnation. Results have shown marked effect on growth parameters and disease incidence has also been reduced significantly.     

Effect of salinity on nodulation,nitrogen fixation and growth of common bean (<Emphasis Type="Italic">Phaseolus vulgaris)</Emphasis> inoculated with rhizobial strains isolated from the Haouz region of Morocco

This study compared growth, nodulation, nitrogen fixation, and nodular enzyme activities in response to salinity in some common bean-rhizobia symbiotic combinations. Seeds of Paulista and Efequince, two varieties of the common bean (Phaseolus vulgaris) were germinated and seedlings were transferred to pots containing vermiculite inoculated with the reference Rhizobium strain CIAT899 or with RhM11 or RhM14, two local strains. Plants were grown in a temperature-controlled glasshouse at 28°C and irrigated with a nutrient solution without NaCl (control) or supplemented with 25 mM NaCl (stressed). Plants were harvested at the flowering stage. The results showed that in controls, inoculation with RhM11 improved plant and nodule growth compared with those inoculated with RhM14 and CIAT 899. NaCl treatment generally had a negative affect on plant and nodule growth. Under the saline treatment, symbiotic nitrogen fixation was not significantly affected in the CIAT899-Paulista, CIAT899-Efequince and RhM11-Paulista combinations. Plant mineral nutrition was negatively affected under salt treatment for all of the tested symbiotic combinations. Inoculation with CIAT899 and RhM11 conferred more plant tolerance to salinity than inoculation with RhM14. The nodular phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase (MDH) exhibited higher activities and were less affected by salinity in plants inoculated with the reference strain CIAT899 than those inoculated with local strains. We conclude that plants inoculated with CIAT899 and RhM11 showed more salinity stress tolerance than those inoculated with RhM14.     

Fluorescent Pseudomonas influences palisade mesophyll development and spatial root development in Phaseolus vulgaris

Three strains of plant growth promoting fluorescent Pseudomonads (HPR6, RRLJ008 and RRLJ134) were studied for their effect on growth and yield of French bean (Phaseolus vulgaris L.) under field conditions. The effect of these strains on nature of root development and leaf palisade tube length were also examined. The strains induced positive response on growth and physiological parameters resulting in higher yield in P. vulgaris. Strain HPR6 produced the most promising results in thickening of leaf palisade layer, spreading of lateral roots and production of root hairs. The increase in specific leaf weight (SLW), net assimilation rate (NAR) and relative growth rate (RGR) by these strains were 68%, 152% and 167%, respectively. The growth and yield parameters were also significantly improved compared to the uninoculated control. Antibiotic resistant mutant strains demonstrated that these bacteria effectively colonized the rhizosphere of French bean. The results suggest that the strains could be developed for field application on a large scale.     

Inhibition of Striga seed germination associated with sorghum growth promotion by soil bacteria

Striga spp. are obligate parasitic weeds of tropical cereals and generally have the same host range as rhizospheric bacteria of the genus Azospirillum. Four strains of Azospirillum brasilense, isolated from soil where sorghum is grown, have been tested for their effect on germination of Striga hermonthica seeds and on cereal (Sorghum vulgare) growth. Two out of four strains assayed significantly inhibited germination of the parasite. Moreover, one of the two strains showed a plant growth promoting (PGPR) effect.     

Effect of transgenic rhizobacteria overexpressing Citrobacter braakii appA on phytate-P availability to mung bean plants

Rhizosphere microorganisms possessing phytase activity are considered important for rendering phytate-P available to plants. In the present study, Citrobacter braakii phytase gene (appA) was over-expressed in rhizobacteria possessing plant growth promoting (PGP) traits for increasing their potential as bioinoculants. AppA was cloned under the lac promoter in the broad host-range expression vector pBBR1MCS2. Transformation of the recombinant construct pCBappA resulted in high constitutive phytase activity in all of the eight rhizobacterial strains belonging to genera Pantoea, Citrobacter, Enterobacter, Pseudomonas (two strains), Rhizobium (two strains) and Ensifer that were studied. Transgenic rhizobacterial strains were found to display varying level of phytase activity, ranging from 10 folds to 538 folds higher than the corresponding control strains. Transgenic derivative of Pseudomonas fluorescens CHA0, a well-characterized plant growth promoting rhizobacterium, showed highest expression of phytase (~8 U/ mg) activity in crude extracts. Although all transformants showed high phytase activity, rhizobacteria having ability to secrete organic acid, showed significantly higher release of P from Ca-phytate in buffered minimal media. AppA over-expressing rhizobacteria showed increased P content, dry weight (shoot) or shoot/ root ratio of mung bean (Vigna radiata) plants, to different extents, when grown in semi solid agar (SSA) medium containing Na-phytate or Ca-phytate as the P sources. This is the first report of over-expression of phytase in rhizobacterial strains and its exploitation for plant growth enhancement.     

应用BOX分子标记技术筛选南苜蓿高效根瘤菌菌株

【目的】应用BOX-PCR技术对12株南苜蓿(Medicago polymorpha)接种根瘤菌菌株在土壤中的竞争结瘤能力进行研究,以占瘤率的高低配合植物生长性状最终确定与南苜蓿共生的高效根瘤菌菌株。【方法】对接种根瘤菌产生的南苜蓿根瘤进行分离培养,选择部分结瘤菌株和12株全部供试接种菌株进行BOX分子指纹图谱研究,经过对图谱的比较与分析获得了各接种菌株的占瘤率。【结果】在供试菌株中,来自于云南盈江的菌株SWF67523占瘤率最高,为93.33%,说明菌株SWF67523具有较强的竞争结瘤能力,该菌株对南苜蓿干重增幅也较高,为100%;菌株SWF67409来自于云南楚雄,其占瘤率略低于菌株SWF67523,但其对提高植物干重的贡献最大(增幅106.5%);来自于云南楚雄的菌株SWF67394占瘤率较低,但其结瘤率高,对植物生长的影响作用也较明显。【结论】将根瘤菌菌株的竞争结瘤能力纳入南苜蓿高效根瘤菌菌株的筛选中,研究获得了一株竞争结瘤能力强、显著提高植物生物量的菌株SWF67523,以及促生根瘤菌菌株SWF67409和SWF67394,为生产高效根瘤菌菌剂提供了物质基础。     

镍胁迫下产铁载体细菌对花生的促生性

【目的】挖掘镍耐受性强、产铁载体活性高的植物根际促生细菌,研究镍胁迫下产铁载体细菌对花生的促生作用及其对花生吸收镍的影响。【方法】利用CAS(Chrome azurol S)培养基对花生根际产铁载体细菌定性筛选及定量测试获得产铁载体能力强的菌株,16S r RNA基因相似性及系统进化分析鉴定产铁载体细菌,并用含Ni~(2+)牛肉膏蛋白胨培养基测试细菌对Ni的耐受性;通过花生盆栽实验,测试花生的株高、根长、生物量、氮磷钾含量及镍含量来分析镍胁迫下产铁载体细菌对花生的影响。【结果】从花生根际分离筛选产铁载体芽孢杆菌5株,其中HSGJ1产铁载体能力最强,培养2 d后产156.56 mg/L的铁载体。HSGJ1对Ni~(2+)具有较强的耐受性,最小致死浓度为150 mg/L。在50、100 mg/kg的Ni~(2+)盆栽基质中,HSGJ1能够有效地促进花生的生长、增加花生的生物量及氮磷钾含量,并使花生根部和地上部分的镍含量降低。【结论】产铁载体芽孢杆菌HSGJ1是一株优良的植物根际促生细菌,可应用于镍污染农耕土壤的作物种植中,以提高作物在镍胁迫下的抗逆性,降低作物对镍的富集量,具有较好的应用价值。     

The bioactivity and fractionation of peptide hydrolysates in cultures of CHO cells

Peptide hydrolysate supplements in mammalian cell cultures provide enhanced growth and productivity. The objective of this study was to compare the bioactivity of ten different commercially available hydrolysates from plant, microbial, and animal sources. The peptide hydrolysates were tested as supplements to cultures of Chinese hamster ovary (CHO) cells that produce human beta interferon (β‐IFN). A soy hydrolysate was shown to support high cell growth but not protein productivity compared to an animal component hydrolysate (Primatone RL). On the other hand, a yeast hydrolysate showed lower cell growth, but comparable productivity of the recombinant protein. Glycosylation analysis showed that the glycan profile of β‐IFN produced in yeast hydrolysate supplemented cultures was equivalent to that from Primatone RL‐supplemented cultures. Fractionation of the yeast hydrolysate and Primatone RL produced a similar protein‐assayed pattern except for one extra peak at around 1 kDa in the Primatone RL profile. A fraction taken at a molecular weight range of 1.5–1.7 kDa showed the highest growth promoting activity in both samples. However, four other fractions in yeast hydrolysate and two in Primatone RL at lower molecular weights showed some growth promoting activity. In conclusion, the yeast hydrolysates provided a good alternative to the animal sourced Primatone RL for high productivity of β‐IFN from CHO cells with equivalent glycosylation. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:584–593, 2014     

Symbiotic performance of some modified Rhizobium etli strains in assays with Phaseolus vulgaris beans that have a high capacity to fix N2

Rhizobium etli and R. tropici form nitrogen-fixing nodules on Phaseolus vulgaris (common bean). In the hope that R. etli strains with additional citrate synthase genes have better carbon economies, merodiploid strains were constructed. Previously, one such construct was shown to have an increased nodulation capacity in the standard bean cultivar Negro Xamapa. In the present work, derivatives from different R. etli strains carrying the R. tropici plasmid-borne or chromosomal citrate synthase gene were constructed and tested for nodulation in bean cultivars selected for their high capacity to fix nitrogen. Nodule numbers were dependent on the strain and the cultivar used. Differences in nodule number were not reflected in plant biomass.     

A new bio-formulation containing plant growth promoting rhizobacterial mixture for the management of sheath blight and enhanced grain yield in rice

Three plant growth promoting rhizobacterial (PGPR) strains, PF1,FP7 and PB2, were tested alone and in combinations for suppression ofrice sheath blight disease and promotion of plant growth underglasshouse and field conditions. The mixture of PGPR strainssignificantly reduced the sheath blight incidence when applied as eitherbacterial suspension through seed, root, foliar and soil application inglasshouse conditions, or as talc-based formulation under fieldconditions, compared to the respective individual strains. The averagemean of disease reduction was 29.2% for single strains and45.1% for mixtures. In addition to disease suppression, treatmentwith mixture of PGPR strains promoted plant growth in terms of increasedplant height and number of tillers, and ultimately grain yield. Theaverage increases in yield for single strains were 17.7%, and25.9% in case of mixture. Mixture of three PGPR strains reduceddisease and promoted growth to a level equivalent to two strainmixtures. Though seed treatment of either single strain or strainmixtures alone could reduce the disease, subsequent application to root,leaves or soil further reduced the disease and enhanced the plantgrowth. The mixture consisting of PF1 plus FP7 was the most effective inreducing the disease and in promoting plant growth and grainyield.     

EFFECT OF METAL TOLERANT PLANT GROWTH PROMOTING BACTERIA ON GROWTH AND METAL ACCUMULATION IN ZEA MAYS PLANTS GROWN IN FLY ASH AMENDED SOIL

The present study was undertaken to examine the effect of the application of fly ash (FA) into Garden soil (GS), with and without inoculation of plant growth promoting bacteria (PGPB), on the growth and metal uptake by Zea mays plants. Three FA tolerant PGPB strains, Pseudomonas sp. PS5, PS14, and Bacillus sp. BC29 were isolated from FA contaminated soils and assessed for their plant growth promoting features on the Z. mays plants. All three strains were also examined for their ability to solubilize phosphate and to produce Indole Acetic Acid (IAA), siderophores, and hydrogencynide acid (HCN) production. Although inoculation of all strains significantly enhanced the growth of plants at both the concentration of FA but maximum growth was observed in plants inoculated with BC29 and PS14 at low level (25%) of FA concentration. The experimental results explored the plant growth promoting features of selected strains which not only enhanced growth and biomass of plants but also protected them from toxicity of FA.     

Plant growth-promoting rhizobacteria modulate root-system architecture in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> through volatile organic compound emission

Extensive communication occurs between plants and microorganisms during different stages of plant development in which signaling molecules from the two partners play an important role. Volatile organic compounds (VOCs) emission by certain plant-growth promoting rhizobacteria (PGPR) has been found to be involved in plant growth. However, little is known about the role of bacterial VOCs in plant developmental processes. In this work, we investigated the effects of inoculation with twelve bacterial strains isolated from the rhizosphere of lemon plants (Citrus aurantifolia) on growth and development of Arabidopsis thaliana seedlings. Several bacterial strains showed a plant growth promoting effect stimulating biomass production, which was related to differential modulation of root-system architecture. The isolates L263, L266, and L272a stimulated primary root growth and lateral root development, while L254, L265a and L265b did not significantly alter primary root growth but strongly promoted lateral root formation. VOC emission analysis by SPME-GC-MS identified aldehydes, ketones and alcohols as the most abundant compounds common to most rhizobacteria. Other VOCs, including 1-octen-3-ol and butyrolactone were strain specific. Characterization of L254, L266 and L272a bacterial isolates by 16S rDNA analysis revealed the identity of these strains as Bacillus cereus, Bacillus simplex and Bacillus sp, respectively. Taken together, our data suggest that rhizospheric bacterial strains can modulate both plant growth promotion and root-system architecture by differential VOC emission.     

In Vitro and In Vivo Plant Growth Promoting Activities and DNA Fingerprinting of Antagonistic Endophytic Actinomycetes Associates with Medicinal Plants

Endophytic actinomycetes have shown unique plant growth promoting as well as antagonistic activity against fungal phytopathogens. In the present study forty-two endophytic actinomycetes recovered from medicinal plants were evaluated for their antagonistic potential and plant growth-promoting abilities. Twenty-two isolates which showed the inhibitory activity against at least one pathogen were subsequently tested for their plant-growth promoting activities and were compared genotypically using DNA based fingerprinting, including enterobacterial repetitive intergenic consensus (ERIC) and BOX repetitive elements. Genetic relatedness based on both ERIC and BOX-PCR generates specific patterns corresponding to particular genotypes. Exponentially grown antagonistic isolates were used to evaluate phosphate solubilization, siderophores, HCN, ammonia, chitinase, indole-3-acetic acid production, as well as antifungal activities. Out of 22 isolates, the amount of indole-3-acetic acid (IAA) ranging between 10–32 μg/ml was produced by 20 isolates and all isolates were positive for ammonia production ranging between 5.2 to 54 mg/ml. Among 22 isolates tested, the amount of hydroxamate-type siderophores were produced by 16 isolates ranging between 5.2 to 36.4 μg/ml, while catechols-type siderophores produced by 5 isolates ranging from 3.2 to 5.4 μg/ml. Fourteen isolates showed the solubilisation of inorganic phosphorous ranging from 3.2 to 32.6 mg/100ml. Chitinase and HCN production was shown by 19 and 15 different isolates, respectively. In addition, genes of indole acetic acid (iaaM) and chitinase (chiC) were successively amplified from 20 and 19 isolates respectively. The two potential strains Streptomyces sp. (BPSAC34) and Leifsonia xyli (BPSAC24) were tested in vivo and improved a range of growth parameters in chilli (Capsicum annuum L.) under greenhouse conditions. This study is the first published report that actinomycetes can be isolated as endophytes from within these plants and were shown to have antagonistic and plant growth promoting abilities. These results clearly suggest the possibility of using endophytic actinomycetes as bioinoculant for plant growth promotion, nutrient mobilization or as biocontrol agent against fungal phytopathogens for sustainable agriculture.     

Impact of soil salinity on the plant-growth – promoting and biological control abilities of root associated bacteria

The effectiveness of plant growth – promoting bacteria is variable under different biotic and abiotic conditions. Abiotic factors may negatively affect the beneficial properties and efficiency of the introduced PGPR inoculants. The aim of this study was to evaluate the effect of plant growth – promoting rhizobacteria on plant growth and on the control of foot and root rot of tomatoes caused by Fusarium solani under different soil salinity conditions. Among the five tested strains, only Pseudomonas chlororaphis TSAU13, and Pseudomonas extremorientalis TSAU20 were able to stimulate plant growth and act as biological controls of foot and root rot disease of tomato. The soil salinity did not negatively affect the beneficial impacts of these strains, as they were able to colonize and survive on the roots of tomato plants under both saline and non-saline soil conditions. The improved plant height and fruit yield of tomato was also observed for plants inoculated with P. extremorientalis TSAU20. Our results indicated that, saline condition is not crucial factor in obtaining good performance with respect to the plant growth stimulating and biocontrol abilities of PGPR strains. The bacterial inoculant also enhanced antioxidant enzymes activities thereby preventing ROS induced oxidative damage in plants, and the proline concentrations in plant tissue that play an important role in plant stress tolerance.     

多功能菌群混合施用的生态效应

从蔬菜地黄瓜根围土壤中经分离筛选,得到两个对黄瓜枯萎病菌(Fusarium oxysporum f.sp.cucumerinum)有抑制作用,并能明显促进黄瓜生长的菌株ZJY-1(Brevibacillus brevis)和ZJY-116(Bacillus subtilis).将这两菌株与一株毒死蜱降解菌DSP3(Alcaligenes faecali)按照不同组合处理黄瓜种子,以研究多功能菌群在环境中发挥生态效应的可行性.结果表明,这两株具有生防和促生功能的菌株与DSP3按不同组合混合后,对黄瓜的防病促生作用均不受影响.同时对黄瓜根围土中毒死蜱含量检测分析发现,DSP3与这两株细菌混和施用后其降解率与单独施用相比没有明显差异.实验初步证明,不同功能的菌株混合施用后可以发挥其生态效应.     

Isolation, characterization, and use for plant growth promotion under salt stress, of ACC deaminase-producing halotolerant bacteria derived from coastal soil

In total, 140 halotolerant bacterial strains were isolated from both the soil of barren fields and the rhizosphere of six naturally growing halophytic plants in the vicinity of the Yellow Sea, near the city of Incheon in the Republic of Korea. All of these strains were characterized for multiple plant growth promoting traits, such as the production of indole acetic acid (IAA), nitrogen fixation, phosphorus (P) and zinc (Zn) solubilization, thiosulfate (S2O3) oxidation, the production of ammonia (NH3), and the production of extracellular hydrolytic enzymes such as protease, chitinase, pectinase, cellulase, and lipase under in vitro conditions. From the original 140 strains tested, on the basis of the latter tests for plant growth promotional activity, 36 were selected for further examination. These 36 halotolerant bacterial strains were then tested for 1- aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Twenty-five of these were found to be positive, and to be exhibiting significantly varying levels of activity. 16S rRNA gene sequencing analyses of the 36 halotolerant strains showed that they belong to 10 different bacterial genera: Bacillus, Brevibacterium, Planococcus, Zhihengliuella, Halomonas, Exiguobacterium, Oceanimonas, Corynebacterium, Arthrobacter, and Micrococcus. Inoculation of the 14 halotolerant bacterial strains to ameliorate salt stress (150 mM NaCl) in canola plants produced an increase in root length of between 5.2% and 47.8%, and dry weight of between 16.2% and 43%, in comparison with the uninoculated positive controls. In particular, three of the bacteria, Brevibacterium epidermidis RS15, Micrococcus yunnanensis RS222, and Bacillus aryabhattai RS341, all showed more than 40% increase in root elongation and dry weight when compared with uninoculated saltstressed canola seedlings. These results indicate that certain halotolerant bacteria, isolated from coastal soils, have a real potential to enhance plant growth under saline stress, through the reduction of ethylene production via ACC deaminase activity.     

5株耐盐碱促生细菌的筛选鉴定及其对红小豆的促生作用

【背景】黑龙江省大庆市地处松嫩平原,土地盐碱化程度较重。盐碱土中含有大量的耐盐碱菌株,其中部分具有特殊的促生功能,可以作为有益促生菌促进植物生长,提高植物对盐碱的抗性。【目的】有效解决土地盐碱化问题,提高粮食作物产量。【方法】采集大庆地区的盐碱土壤为实验材料,在NaHCO_3终浓度为50 mmol/L、pH 9.0的条件下对土壤中耐盐碱细菌进行分离,用功能性培养基进行促生功能细菌菌株的筛选,并对相应促生物质产量进行测定;挑选促生功能较全、促生效果较好的细菌菌株,采用形态学观察、生理生化法以及16S rRNA基因序列分析法进行菌种鉴定,以确定菌株的分类学地位;在pH 8.5、15 mmol/L Na HCO3胁迫条件下测试施用促生菌株对红小豆种子发芽率、根长、芽长及插条生根数和根长的影响,以验证促生效果。【结果】对筛选获得的细菌菌株进行鉴定,29号细菌为卓贝尔氏菌属(Zobellella sp.),23、34、36和41号细菌属于盐单胞菌属(Halomonas sp.)。5株细菌均具有固氮、产植物激素吲哚乙酸(Indole-3-Acetic Acid,IAA)及ACC脱氨酶功能,34号和23号细菌具有最高植物激素IAA和ACC脱氨酶产量,分别达到了17.66 mg/L和0.31 U/mg。另外,23号细菌具有产铁载体能力,铁载体产量为3.19%;29和41号细菌具有溶有机磷功能,溶磷量分别为20.05 mg/L和34.61 mg/L。植物促生试验结果显示,在盐碱胁迫条件下,红小豆种子接菌后种子的发芽率和根长分别提高了41.67%和32.63%以上;红小豆插条接菌后,幼苗的根长和生根数与盐碱胁迫对照相比分别提升了129%和160%以上。【结论】这5株耐盐碱促生细菌能够缓解盐碱胁迫对红小豆生长的抑制作用,可以较好地促进其根系生长发育,可为研制耐盐碱促生菌肥提供优良菌种。     

花生种子相关促生菌分离鉴定及功能评价

【背景】利用微生物促进植物健康生长是农业可持续发展的重要方向之一,而种子相关的促生菌可在植物生命周期早期与植物相互作用,对植物健康生长具有重要意义。【目的】发掘与利用种子相关促生菌的前提是筛选获得促生菌菌种资源,验证其益生能力,为其进一步应用与机理研究提供依据与支持。【方法】以花生种子为研究对象,从种子表面及种子内部分离纯化多株菌,测定菌株的固氮、解磷、解钾、吲哚乙酸合成和铁载体合成等促生能力,并验证菌株对常见植物病原菌的生长抑制特性;通过16S rRNA基因序列进行系统发育分析,确定分类地位;通过生物膜形成能力及根际定殖能力测定菌株在植物根际的生存能力;最后通过催芽及盆栽试验测定菌株对花生种子发芽及幼苗生长的影响。【结果】从花生种子表面、种子内和胚根内分离筛选到41株菌,均有吲哚乙酸合成能力,其中35株有固氮能力,2株有铁载体分泌能力,14株有植物病原菌生长抑制能力。各选一株为代表的菌株,即PS3、PE5和PR5,经16S rRNA基因序列比对分析鉴定为芽孢杆菌属(Bacillus)。PS3、PE5和PR5均可在MSgg液体培养基表面形成褶皱较强的生物膜,也可在花生根际形成有效定殖。催芽试验结果表明经过促生菌浸种后花生种子萌发率明显提高,在第2天时,PS5将发芽率由14.17%提高至38.33%,PE5发芽率提高至30.83%,PR5发芽率提高至39.17%。三株菌能够明显促进花生幼苗生长,PS5对花生幼苗苗高、根长、鲜重和干重分别提高21.82%、22.20%、37.11%和35.64%,PE5分别提高17.45%、18.93%、26.10%和21.18%,PR5分别提高23.11%、23.92%、38.66%和37.47%。【结论】筛选获得的花生种子相关促生菌,具有促进植物生长的潜力,明显促进种子萌发及幼苗生长,是良好的促生菌生物资源,具有较好的应用潜力。