Plant growth-promoting properties and anti-fungal activity of endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta in arid lands

Endophytes,as crucial components of plant microbial communities,significantly contribute to enhancing the absorption of nutrients such as nitrogen and phosphorus by their hosts,promote plant growth,and degrade pathogenic fungal mycelia.In this study,an experiment was conducted in August 2022 to explore the growth-promoting potential of endophytic bacterial strains isolated from two medical plant species,Thymus altaicus and Salvia deserta,using a series of screening media.Plant samples of Thymus altaicus and Salvia deserta were collected from Zhaosu County and Habahe County in Xinjiang Uygur Autonomous Region,China,in July 2021.Additionally,the inhibitory effects of endophytic bacterial strains on the four pathogenic fungi(Fusarium oxysporum,Fulvia fulva,Alternaria solani,and Valsa mali)were determined through the plate confrontation method.A total of 80 endophytic bacterial strains were isolated from Thymus altaicus,while a total of 60 endophytic bacterial strains were isolated from Salvia deserta.The endophytic bacterial strains from both Thymus altaicus and Salvia deserta exhibited plant growth-promoting properties.Specifically,the strains of Bacillus sp.TR002,Bacillus sp.TR005,Microbacterium sp.TSB5,and Rhodococcus sp.TR013 demonstrated strong cellulase-producing activity,siderophore-producing activity,phosphate solubilization activity,and nitrogen-fixing activity,respectively.Out of 140 endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta,104 strains displayed anti-fungal activity against Fulvia fulva,Alternaria solani,Fusarium oxysporum,and Valsa mali.Furthermore,the strains of Bacillus sp.TR005,Bacillus sp.TS003,and Bacillus sp.TSB7 exhibited robust inhibition rates against all the four pathogenic fungi.In conclusion,the endophytic bacterial strains from Thymus altaicus and Salvia deserta possess both plant growth-promoting and anti-fungal properties,making them promising candidates for future development as growth-promoting agents and biocontrol tools for plant diseases.

Plant growth-promoting rhizobacteria(PGPR)and its mechanisms against plant diseases for sustainable agriculture and better productivity

Plant growth-promoting rhizobacteria(PGPR)are specialized bacterial communities inhabiting the root rhizosphere and the secretion of root exudates helps to,regulate the microbial dynamics and their interactions with the plants.These bacteria viz.,Agrobacterium,Arthobacter,Azospirillum,Bacillus,Burkholderia,Flavobacterium,Pseudomonas,Rhizobium,etc.,play important role in plant growth promotion.In addition,such symbiotic associations of PGPRs in the rhizospheric region also confer protection against several diseases caused by bacterial,fungal and viral pathogens.The biocontrol mechanism utilized by PGPR includes direct and indirect mechanisms direct PGPR mechanisms include the production of antibiotic,siderophore,and hydrolytic enzymes,competition for space and nutrients,and quorum sensing whereas,indirect mechanisms include rhizomicrobiome regulation via.secretion of root exudates,phytostimulation through the release of phytohormones viz.,auxin,cytokinin,gibberellic acid,1-aminocyclopropane-1-carboxylate and induction of systemic resistance through expression of antioxidant defense enzymes viz.,phenylalanine ammonia lyase(PAL),peroxidase(PO),polyphenyloxidases(PPO),superoxide dismutase(SOD),chitinase andβ-glucanases.For the suppression of plant diseases potent bio inoculants can be developed by modulating the rhizomicrobiome through rhizospheric engineering.In addition,understandings of different strategies to improve PGPR strains,their competence,colonization efficiency,persistence and its future implications should also be taken into consideration.

Effect of Plant Growth-Promoting Rhizobacteria at Various Nitrogen Rates on Corn Growth

Plant growth-promoting rhizobacteria (PGPR) colonize plant roots and promote plant growth by producing and secreting various chemical regulators in the rhizosphere. With the recent interest in sustainable agriculture, an increasing number of researchers are investigating ways to improve the efficiency of PGPR use to reduce chemical fertilizer inputs needed for crop production. Accordingly, greenhouse studies were conducted to evaluate the impact of PGPR inoculants on biomass production and nitrogen (N) content of corn (Zea mays L.) under different N levels. Treatments included three PGPR inoculants (two mixtures of PGPR strains and one control without PGPR) and five N application levels (0%, 25%, 50%, 75%, and 100% of the recommended N rate of 135 kg N ha−1). Results showed that inoculation of PGPR significantly increased plant height, stem diameter, leaf area, and root morphology of corn compared to no PGPR application under the same N levels at the V6 growth stage, but few differences were observed at the V4 stage. PGPR with 50% of the full N rate produced corn biomass and N concentrations equivalent to or greater than that of the full N rate without inoculants at the VT stage. In conclusion, mixtures of PGPR can potentially reduce inorganic N fertilization without affecting corn plant growth parameters. Future research is needed under field conditions to determine if these PGPR inoculants can be integrated as a bio-fertilizer in crop production nutrient management strategies.

Potential seed germination-enhancing plant growth-promoting rhizobacteria for restoration of Pinus chiapensis ecosystems

Rhizosphere soil samples of three Pinus chiapensis sites were analyzed for their physicochemical properties,soil bacteria isolated and screened in vitro for growthpromoting abilities.Nine isolates that showed promise were identified to five genera Dyella,Luteimonas,Euterobacter,Paraburkholderia and Bacillus based on the sequences of16 S rRNA gene.All the strains were isolated from nondisturbed stands.These bacteria significantly decreased germination time and increased sprout sizes.Indole acetic acid and gibberellin production and phosphate solubilisation were detected.Results indicate that these biochemicals could be essential for P.chiapensis distribution and suggest the possibility that PGPR inoculation on P.chiapensis seeds prior to planting could improve germination and possibly seedling development.

Synergistic combination of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria modulates morpho-physiological characteristics and soil structure in Nitraria tangutorum bobr.Under saline soil conditions

Nitraria tangutorum Bobr.,a typical xero-halophyte,can be used for vegetation restoration and reconstruction in arid and semiarid regions affected by salinity.However,global climate change and unreasonable human activity have exacerbated salinization in arid and semi-arid regions,which in turn has led to the growth inhibition of halophytes,including N.tangutorum.Arbuscular mycorrhizal fungi(AMF)and plant growth-promoting rhizobacteria(PGPR)have the potential to improve the salt tolerance of plants and their adaptation to saline soil environments.In this study,the effects of single and combined inoculations of AMF(Glomus mosseae)and PGPR(Bacillus amyloliquefaciens FZB42)on N.tangutorum were evaluated in severe saline soil conditions.The results indicate that AMF and PGPR alone may not adapt well to the real soil environment,and cannot ensure the effect of either growth promotion or salt-tolerance induction on N.tangutorum seedlings.However,the combination of AMF and PGPR significantly promoted mycorrhizal colonization,increased biomass accumulation,improved morphological development,enhanced photosynthetic performance,stomatal adjustment ability,and the exchange of water and gas.Co-inoculation also significantly counteracted the adverse effect of salinity on the soil structure of N.tangutorum seedlings.It is concluded that the effectiveness of microbial inoculation on the salt tolerance of N.tangutorum seedlings depends on the functional compatibility between plants and microorganisms as well as the specific combinations of AMF and PGPR.

Application Progress of Plant Growth-promoting Bacteria in Crops

Plant growth-promoting bacteria(PGPBs)can promote plant growth and improve crop yield.They can induce plant systemic resistance to resist biotic and abiotic stresses.In recent years,with the development of green ecological agriculture,new biological fertilizers such as microbial inocula and microbial fertilizers based on PGPBs have been gradually applied in crop planting.Based on plant growth promotion and disease control,the application progress of PGPBs in crops from the aspects of growth promotion mechanism,growth promotion effect,resistance to biological and abiotic stresses were discussed,aiming to provide reference for the relevant research and application of PGPBs in crops.

植物根际促生菌在烟草根茎类病害防治中的应用研究进展

烟草是重要的经济作物,经济价值高。烟草根茎类病害的发生导致一定的烟草损失。本文阐述了烟草根黑腐病、烟草黑胫病和烟草青枯病等烟草根茎类病害的发生和危害,分析了烟草根茎类病害的防治现状,包括农业防治、化学防治和生物防治等内容,提出了植物根际促生菌的研究进展,探讨了其作用机制及在防治烟草病害中的应用前景,总结了用于防治烟草病害的植物根际促生菌主要种类,提出了相关展望,以期为有效防治烟草根茎类病害和推广应用植物根际促生菌提供参考。

Rice(Oryza sativa L.)plant protection using dual biological control and plant growth-promoting agents:Current scenarios and future prospects

Various microorganisms live in association with different parts of plants and can be harmful,neutral,or beneficial to plant health.Some microbial inhabitants of plants can control plant diseases by contesting with,predating on,or antagonizing plant pathogens and by inducing systems for plant defense.A range of methods,including plant growth-promoting microorganisms(PGPMs)as biological control agents(BCAs)(BCA-PGPMs)are used for the biological management and control of plant pathogens.Some BCAs interact with plants by inducing resistance or priming plants without direct interaction with the pathogen.Other BCAs operate via nutrient competition or other mechanisms to modulate the growth conditions for the pathogen.Generally,PGPMs can be applied alone or together with other chemicals or carriers to control various crop diseases.This review highlights the effective types of BCA-PGPMs and their applications,roles,carrier based-formulations,and responses to rice(Oryza sativa L.)pathogens.Future plant disease management prospects are promising,and growers’increasing demand for BCA-PGPM products can be exploited as an effective approach to the management of plant diseases,as well as to improve yield,environmental protection,biological resources,and agricultural system sustainability.

Mutual Information Flow between Beneficial Microorganisms and the Roots of Host Plants Determined the Bio-Functions of Biofertilizers

Modern agriculture is facing new challenges in which ecological and molecular approaches are being integrated to achieve higher crop yields while minimizing negative impacts on the environment. The application of biofertilzers could meet this requirement. Biofertilizer is a natural organic fertilizer that helps to provide all the nutrients required by the plants and helps to increase the quality of the soil with a natural microorganism environment. This paper reviewed the types of biofertilzers, the biological basic of biofertilizers in plant growth promotion. This paper also assayed the bidirectional information exchange between plant-microbes in rhizoshpere and the signal pathway of plant growth- promoting rhizobacteria (PGPR) and plant growth-promoting fungi (PGPF) in the course of plant infection. At last, the challenges of the application and the promising future of biofertilizers were also discussed.

Application of PCR primer sets for detection of <i>Pseudomonas</i>sp. functional genes in the plant rhizosphere

Plant growth promoting pseudomonads play an important role in disease suppression and there is considerable interest in development of bio-marker genes that can be used to monitor these bacteria in agricultural soils. Here, we report the application ofa PCR primer sets targeting genes encoding the main antibiotic groups. Distribution of the genes was variably distributed across type strains of 28 species with no phylogenetic groupingfor the detected antibioticsgenes, phlD for 2,4-diacetylphloroglucinol (2,4-DAPG) and phzCD for phenazine-1-carboxylic acid or hcnBC for hydrogen cyanide production. Analysis of field soils showed that primer sets for phlD and phzCD detected these genes in a fallowed neutral pH soil following wheat production, but that the copy numbers were below the detection limits in bulk soils having an acidic pH. In contrast, PCR products for the phzCD, pltc and hcnBc genes were detectable in mature root zones following plantingwith wheat. The ability to rapidly characterize populations of antibiotics producers using specific primer sets will improve our ability to assess the impacts of management practices on the functional traits of Pseudomonas spp. populations in agricultural soils.

Advances in the studies on symbiotic arbuscular mycorrhizal fungi of traditional Chinese medicinal plants

Arbuscular mycorrhizal(AM)fungi reside in the rhizosphere and form mutualistic associations with plant roots.They promote photosynthesis,improve stress resistance,and induce secondary metabolite biosynthesis in host medicinal plants.The AM fungi that are symbiotic with medicinal plants comprise a wide array of species and have abundant germplasm resources.Though research on the AM fungi in medicinal plants began relatively recently,it has nonetheless become an investigative hot spot.Several scholars have explored the diversity and the growth-promoting effects of mycorrhizal fungi in hundreds of medicinal plants.Current research on symbiotic AM fungi in medicinal plants has focused mainly on the effects of inoculating host plants with symbiotic mycorrhizal fungi.However,research on the symbiotic AM fungi in medicinal plants continues to expand,and further study is required to determine the mechanisms by which AM fungi interact with host plants.This paper introduces the diversity of symbiotic AM fungi of medicinal plants and the effects of AM fungi on rhizosphere soil of medicinal plants,including soil structure,microbiota,enzyme activities,etc.This review focuses on the effects of AM fungi on medicinal plants,including antioxidant enzyme systems,drought resistance,nutrient absorption profiles of macroand micronutrients,accumulation of secondary metabolites such as terpenes,phenolic compounds,and nitrogenous compounds,and prevention of diseases.This review is expected to provide a reference for the application of AM fungi in medicinal plant cultivation,biological control,resource conservation,and the sustainable development of the traditional Chinese medicine industry.

Plant Growth Promoting Rhizobacteria as Biological Control Agent in Rice

The use of agrochemical products to combat diseases in crops has adverse effects on the environment and human health. Plant growth promoting rhizobacterium (PGPR) has been increasingly proposed as an eco-friendly alternative in agriculture. PGPRs have beneficial effects not only in promoting plant growth but also have shown their potential as biological control agent, being able to inhibit plant pathogens. Here, we investigated the use of PGPR Paraburkholderia sp. strain SOS3 to provide disease protection in rice (Oryza sativa L.). The antagonistic activity of SOS3 against five fungal pathogens of rice was assessed by dual culture on plates and on rice seedlings. The results showed that on plate assay, SOS3 inhibits the growth of Curvularia lunata, Rhizoctonia solani, Pyricularia oryzae, Helminthosporium oryzae, and Fusarium moniliforme by 17.2%, 1.1%, 8.3%, 32.5%, and 35.4%, respectively. When inoculated on rice seeds, SOS3 promotes seed germination and significantly reduces disease symptoms in plants infected with R. solani. These results suggest that SOS3 has a great potential to be used in rice agriculture to combat the “Sheath Blight” disease.

Effect of arsenic on tolerance mechanisms of two plant growth-promoting bacteria used as biological inoculants

Bacterial ability to colonize the rhizosphere of plants in arsenic（As） contaminated soils is highly important for symbiotic and free-living plant growth-promoting rhizobacteria（PGPR）used as inoculants, since they can contribute to enhance plant As tolerance and limit metalloid uptake by plants. The aim of this work was to study the effect of As on growth,exopolysaccharide（EPS） production, biofilm formation and motility of two strains used as soybean inoculants, Bradyrhizobium japonicum E109 and Azospirillum brasilense Az39. The metabolism of arsenate（As（V）） and arsenite（As（III）） and their removal and/or possible accumulation were also evaluated. The behavior of both bacteria under As treatment was compared and discussed in relation to their potential for colonizing plant rhizosphere with high content of the metalloid. B. japonicum E109 growth was reduced with As（III）concentration from 10 μM while A. brasilense Az39 showed a reduction of growth with As（III） from 500 μM. EPS and biofilm production increased significantly under 25 μM As（III）for both strains. Moreover, this was more notorious for Azospirillum under 500 μM As（III）,where motility was seriously affected. Both bacterial strains showed a similar ability to reduce As（V）. However, Azospirillum was able to oxidize more As（III）（around 53%） than Bradyrhizobium（17%）. In addition, both strains accumulated As in cell biomass. The behavior of Azospirillum under As treatments suggests that this strain would be able to colonize efficiently As contaminated soils. In this way, inoculation with A. brasilense Az39 would positively contribute to promoting growth of different plant species under As treatment.

Selection and validation of reference genes for quantitative real-time polymerase chain reaction analyses of Serratia ureilytica DW2

Background:Serratia ureilytica DW2 is a highly efficient phosphate-solubilizing bacteria isolated from Codonopsis pilosula rhizosphere soil that can promote the growth of C.pilosula;nonetheless,until now,no validated reference genes from the genus Serratia have been reported that can be used for the normalization of quantitative real-time polymerase chain reaction(RT–qPCR)data.Methods:To screen stable reference genes of S.ureilytica DW2,the expression of its eight candidate reference genes(16S rRNA,ftsZ,ftsA,mreB,recA,slyD,thiC,and zipA)under different treatment conditions(pH,temperature,culture time,and salt content)was assayed by RT–qPCR.The expression stability of these genes was analyzed using different algorithms(geNorm,NormFinder,and BestKeeper).To verify the reliability of the data,the expression of the glucose dehydrogenase(gdh)gene under different soluble phosphate levels was quantified using the most stably expressed reference gene.Results:The results showed that the zipA and 16S rRNA genes were the most stable reference genes,and the least stable genes were thiC and recA.The expression of gdh was consistent with the phosphate solubilization ability on plates containing the National Botanical Research Institute phosphate growth medium.Conclusion:Therefore,this study provides a stable and reliable reference gene of Serratia for the accurate quantification of functional gene expression in future studies.

Arbuscular mycorrhiza and plant growth promoting endophytes facilitates accumulation of saponin under moderate drought stress

Objective: Paris polyphylla var. yunnanensis, one of the important medicinal plant resources in Yunnan,China, usually takes 6–8 years to be harvested. Therefore, it is urgent to find a method that can not only shorten its growth years, but also improve its quality. In this study, we examined the effects of a combination treatment of arbuscular mycorrhizal fungi(AMF) and plant growth-promoting endophytes(PGPE)and drought stress on the accumulation of saponins in it.Methods: P. polyphylla var. yunnanensis was infected with a mixture of AMF and PGPE under drought stress. The content of saponins, as well as morphological, physiological, and biochemical indicators, were all measured. The UGTs gene related to saponin synthesis was obtained from transcriptome data by homologous comparison, which were used for RT-PCR and phylogenetic analysis.Results: Regardless of water, AMF treatment could infect the roots of P. polyphylla var. yunnanensis, however double inoculation with AMF and PGPE(AMF + PGPE) would reduce the infection rate of AMF. Plant height, aboveground and underground fresh weight did not differ significantly between the single inoculation AMF and the double inoculation treatment under different water conditions, but the inoculation treatment significantly increased the plant height of P. polyphylla var. yunnanensis compared to the noninoculation treatment. Single inoculation with AMF considerably increased the net photosynthetic rate,stomatal conductance, and transpiration rate of P. polyphylla var. yunnanensis leaves under various water conditions, but double inoculation with AMF + PGPE greatly increased the intercellular CO2concentration and chlorophyll fluorescence parameter(Fv/Fm). Under diverse water treatments, single inoculation AMF had the highest proline content, whereas double inoculation AMF + PGPE may greatly improve the amount of abscisic acid(ABA) and indoleacetic acid(IAA) compared to normal water under moderate drought. Double inoculation AMF + PGPE treatment improved the proportion of N, P, and K in the rhizome of P. polyphylla var. yunnanensis under various water conditions. Under moderate drought stress,AMF + PGPE significantly enhanced the contents of P. polyphylla var. yunnanensis saponins I, II, VII, and total saponins as compared to normal water circumstances. Farnesyl diphosphate synthase(FPPS),Geranyl pyrophosphate synthase(GPPS), Cycloartenol synthase(CAS), and Squalene epoxidase(SE1) were the genes that were significantly up-regulated at the same time. The amount of saponins was favorably linked with the expression of CAS, GPPS, and SE1. Saponin VI content and glycosyl transferase(UGT)010922 gene expression were found to be substantially associated, as was saponin II content and UGT010935 gene expression.Conclusion: Under moderate drought, AMF + PGPE was more conducive to the increase of hormone content, nutrient absorption, and total saponin content in P. polyphylla var. yunnanensis, and AMF + PGPE could up regulate the expression of key genes and UGTs genes in one or more steroidal saponin synthesis pathways to varying degrees, thereby stimulating the synthesis and accumulation of steroidal saponins in the rhizome of P. polyphylla var. yunnanensis. The combination of AMF and PGPE inoculation, as well as adequate soil drought, reduced the buildup of saponins in P. polyphylla var. yunnanensis and increased its quality.

不同复合菌剂对甘薯产量和品质的影响

植物促生菌对植物的生长发育和品质形成具有一定的影响。本文以甘薯品种朝日8号为试验材料,研究不同复合菌剂对甘薯产量和品质的影响。结果表明:不同复合菌剂对甘薯产量均有一定影响,其中以组合1[含苏云金芽孢杆菌(Bt1)、肠杆菌属(Es)、戊糖片球菌(Pp1)]对甘薯的增产效果最好,与对照相比,增产率达到17.03%;复合菌剂处理后,薯块大部分营养品质指标得到了提升,DPPH自由基清除率变幅为64%~95%,说明复合菌剂对甘薯品质也产生了一定影响。

Efficacy of Bacillus subtilis MBI 600 Against Sheath Blight Caused by Rhizoctonia solani and on Growth and Yield of Rice

Rice sheath blight disease （ShB）, caused by Rhizoctonia solani, gives rise to significant grain yield losses. The present study evaluated the efficacy of Integral, the commercial liquid formulation of Bacillus subtilis strain MBI 600, against rice ShB and for plant growth promotion. In greenhouse studies, four log concentrations of Integral （from 2.2×10^6 to 2.2×10^9 cfu/mL） were used as seed treatment （ST）. After 25 d, seedlings were dipped （SD） into Integral prior to transplanting. At 30 d after transplanting （DAT）, leaf sheaths were inoculated with immature sclerotia of the pathogen. At 45 DAT, a foliar spray （FS） with Integral was applied to some treatments. The fungicide control was 50% carbendazim at 1.0 g/L, and a nontreated control was also included. Overall, there were 10 treatments, each with five replications. ShB severity was rated at 52 DAT, and seedling height and number of tillers per plant were rated at 60 DAT. In 2009, two field trials evaluated Integral at 2.2×10^8 and 2.2×10^9 cfu/mL. Integral was applied as ST, and seedlings were produced in a nursery bed. After 32 d, seedlings were treated with Integral as SD and transplanted into 10 m^2 blocks. Foliar sprays were given at 45 and 60 DAT. There were seven treatments, each with eight replications arranged as a factorial randomized complete block design. At 20 DAT, the plots were broadcast inoculated with R. solani produced on rice grains. Seedling height before transplanting, ShB severity at 90 DAT, and grain yield at harvest were recorded. Integral at 2.2×10^9 cfu/mL provided significant increase of seedling heights over other treatments under greenhouse conditions. The Integral treatments of ST ＋ SD ＋ FS at 2.2×10^9 cfu/mL significantly suppressed ShB over other treatments. In field studies, Integral provided significant increase of seedling height in nursery, and number of tillers per plant, compared with the control. ShB severity was significantly suppressed with higher concentrations of Integral compared to lower concentrations. Grain yield were the highest at an Integral concentration of 2.2×10^9 cfu/mL. Overall, Integral significantly reduced ShB severity, enhanced seedling growth, number of tillers per plant and grain yield as ST ＋ SD ＋ FS at the concentration of 2.2×10^9 cfu/mL under the conditions evaluated.

植物根围促生细菌菌剂增强玉米干旱耐受性研究

选用植物根围促生细菌(PGPR)菌剂BBS处理玉米幼苗,研究干旱胁迫下玉米幼苗叶片相关生理特性及基因表达差异。结果表明,干旱胁迫15 d后,BBS处理组玉米幼苗的萎蔫程度显著低于对照组;处理组植株叶片MDA含量仅为对照组的74.35%,叶片脯氨酸和可溶性糖含量分别是对照组的3.39倍和1.07倍;处理组植株叶片ZmP5CS1的表达水平及SOD活性均显著高于对照组;BBS处理组植株叶片在干旱胁迫过程中一直保持较低的H_2O_2含量。研究得出,BBS处理能够有效减缓干旱胁迫对玉米幼苗造成的伤害,进而加速正常浇水后的恢复。处理组植株叶片NCED1和ZmDREB2.7的高水平表达也表明干旱胁迫下玉米幼苗与BBS的互作过程可能有依赖ABA信号途径及不依赖ABA信号途径的共同参与。

植物根际促生细菌在烤烟提质增产中的作用

为分析植物根际促生细菌(Plant growth-promoting rhizobacteria,PGPR)在烤烟提质增产中的作用,从攀枝花烟区优质烟株根际土壤中分离筛选出促生性好且相互之间不存在拮抗作用的产吲哚乙酸菌、溶磷菌和解钾菌,这3种细菌的混合物即为多功能PGPR混合菌剂。采用盆栽试验和大田试验,研究了多功能PGPR混合菌剂对烤烟提质增产的作用。结果表明:多功能PGPR混合菌剂可改善烤烟的农艺性状及烟叶的化学品质,降低烤烟发病率。以复合肥为底肥施加PGPR混合菌剂可使中上等烟叶比例提高22.0%;以复合肥和有机肥为底肥,施加PGPR混合菌剂可使中上等烟叶比例和产值分别提高34.5%和26.4%。

具有ACC脱氨酶活性的红枣根际促生菌株的分离筛选及其促生效果研究

采用定向富集法从红枣根际土壤分离筛选具有ACC脱氨酶活性的细菌,同时检测其产生长素(IAA)、固氮和解磷等促生特性。结合形态特征和16S rDNA序列分析对菌株进行鉴定,并采用盆栽试验验证3株高效产ACC脱氨酶的根际促生菌株Pseudomonas fluorescens、Pseudomonas putida和Serratia plymuthica对红枣植株生长的影响。结果表明:1)从红枣根际共分离出10株产ACC脱氨酶的菌株,其ACC脱氨酶活性在14.23~433.05μmol/(mg·h)。这些菌株都具有产IAA、固氮和解无机磷能力。2)经鉴定,10株菌株分别属于假单胞菌属(Pseudomonas)、芽孢杆菌属(Bacillus)和沙雷氏菌属(Serratia)。3)接种Pseudomonas putida菌剂和Serratia plymuthica菌剂均可显著促进红枣植株生长发育,提高植株株高、生物量、叶片氮及磷含量。2种菌株的接种效应明显优于Pseudomonas fluorescens菌剂,且复合菌株应用促生效果优于单一菌株。