CN113186112B

CN113186112B - Rhizobium rosenbergii FN2, microbial inoculum thereof and application thereof in field of soil improvement

Info

Publication number: CN113186112B
Application number: CN202011511091.7A
Authority: CN
Inventors: 张建; 庄林岚; 周璐璐; 胡振; 谢慧君; 梁爽; 王禄山
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-12-21
Filing date: 2020-12-21
Publication date: 2022-06-24
Anticipated expiration: 2040-12-21
Also published as: CN113186112A

Abstract

The invention particularly relates to rhizobium rosette FN2, a microbial inoculum thereof and application in the field of soil improvement. The soil salinization can seriously affect the soil ecological environment and the sustainable development of agriculture, and the microbial preparation with the nitrogen fixation effect has good environmental compatibility when being used for improving the saline-alkali soil, thereby being a sustainable development mode. The invention provides Rhizobium rosette (Rhizobium rosettiformens) FN2, which has good nitrogen fixation and saline-alkali resistance effects and can be used for developing soil improvement preparations.

Description

Rhizobium roseoantum FN2, microbial inoculum thereof and application in soil improvement field

Technical Field

The invention belongs to the technical field of soil improvement engineering strains, and particularly relates to Rhizobium rosette (Rhizobium rosettiformens) FN2, a microbial inoculum thereof and application thereof in the field of soil improvement.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The total soil area in the world is about 132 hundred million hectares, with available land area not exceeding 70 hundred million hectares and arable land area being only about 15 hundred million hectares. In the only arable land, about 23% of the land is saline soil, up to 3.4 hundred million hectares in area, 37% of the soil is sodium-containing soil, up to 5.6 hundred million hectares in area; that is, nearly 10% of the available soil in the world is subjected to salt stress. Moreover, saline-alkali soil is distributed not only in desert and semi-desert regions, but also in fertile river basins, coastal regions, alluvial plains and irrigation areas. Salinization not only damages the structure and properties of soil and hinders the growth and development of crops, but also ultimately affects the ecological environment and sustainable development of agriculture.

Under saline-alkali stress, the number of microorganisms in soil is remarkably reduced, and the microbial community structure, microbial community diversity, microbial community function and other aspects are changed, so that nutrients such as nitrogen, phosphorus and the like are slowly released. Thereby further influencing the soil microbial community and increasing the toxic action of saline-alkali stress on the soil microbial community. With the increase of the salt concentration, the osmotic effect is correspondingly increased, single-ion toxicity causes soil nutrition imbalance, so that the growth of soil microorganisms and enzyme synthesis are influenced, and the number of bacteria, actinomycetes and fungi in soil is in a decreasing trend. Because the soil contains saline-alkali ion components, the number of microorganisms in the saline-alkali soil is obviously less than that of normal agricultural soil. In addition, the saline-alkali components can change the adaptability of soil microorganisms to the environment, inhibit the activity of the soil microorganisms and reduce the activities of nitrobacteria, phosphorus bacteria and phosphorus enzymes in the soil, so that the nitrification capability of nitrogen in the soil is inhibited, and the soil microorganisms can not adapt to the environment under adverse conditions to reduce or even lose the activity of the microorganisms.

The nitrogen-fixing bacteria can convert nitrogen in the atmosphere into a form which can be used by microorganisms and plants. Azotobacter includes Azotobacter, Azomonas, Yersinia, and Dexas. The nitrogen-fixing bacteria are added into the saline-alkali soil, so that the microenvironment of the saline-alkali soil can be improved, the utilization rate of nitrogen in the soil can be improved, and the growth of crops can be promoted. The microorganism is adopted as the soil improvement preparation, the affinity to the environment is better, no additional treatment burden is caused, and the development of the microorganism preparation with the soil improvement activity as far as possible has important significance for ecological environment construction and agricultural development.

Disclosure of Invention

Based on the above research background, the present invention aims to provide a novel strain for improving saline-alkali soil. In order to achieve the purpose, the invention screens the Rhizobium roseum Rhizobium FN2 in the delta area of the east-Yinghuanghe Delta, identifies the Rhizobium rosette (Rhizobium rosettiformens) by morphological characteristics, physiological and biochemical characteristics and 16S rDNA sequence analysis, determines the salt resistance and nitrogen fixation capacity of the Rhizobium rosette and the actual application condition of saline-alkali soil, and provides strain resources for improving the saline-alkali soil.

Based on the research content, the invention provides a Rhizobium rosette (Rhizobium rosettiformens) FN2 strain, wherein the strain is preserved in China general microbiological culture Collection center (CGMCC) at 12 months and 7 days in 2020, and the address is as follows: the biological preservation number of the Xilu No. 1 Hospital No. 3 of the Chaojing Chaoyang district is: CGMCC No. 21307.

Related research on Rhizobium rosette (Rhizobium rosettF.) is almost blank at present in the field, and a strain of Rhizobium rosettf (Rhizobium rosettf.) disclosed in patent CN107354099A shows that the strain has a promoting effect on the accumulation of oil and fat in Aphanizomenon flavus. The research of the invention provides research guidance for the application of rhizobium rosette.

Based on the strain, the research of the invention proves that the strain can generate the self-generated azotobacter in the culture process, so that the strain and the culture of the strain are expected to be applied to the preparation of soil improvement preparations. The technical personnel in the field can obtain the microbial inoculum according to the conventional research means, and mix the microbial inoculum with other active substances and conventional auxiliary materials to obtain a soil improvement preparation.

In a second aspect of the invention, there is provided a microbial inoculum comprising Rhizobium rosette (Rhizobium rosettiformens) FN2 and/or a culture of the bacteria of the first aspect.

In a third aspect of the present invention, there is provided an application of the strain of the first aspect and the microbial inoculum of the second aspect in the field of soil improvement.

In a fourth aspect of the present invention, there is provided a soil conditioner comprising Rhizobium rosette (Rhizobium rosettiformens) FN2 of the first aspect and/or a microbial inoculum of the second aspect.

The beneficial effects of one or more technical schemes are as follows:

1. the research result firstly fills the blank of the research aspect of the rhizobium rosette in the field, enriches the related research, provides a new application direction of the rhizobium rosette, and has good guiding significance for the research of the rhizobium rosette in the future.

2. The invention provides application of rhizobium rosenbergii in preparing a soil conditioner, wherein the rhizobium rosenbergii has good saline-alkali resistance, helps plants to improve stress resistance, and improves the planting rate of the plants in saline-alkali soil.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a pictorial representation of a colony of Rhizobium rosettiformis (Rhizobium rosettiformis) FN2 described in example 1;

FIG. 2 is an electron micrograph of Rhizobium rosettiformis (Rhizobium rosettiformis) FN2 described in example 1;

FIG. 3 is a tree diagram of the 16S rDNA phylogenetic tree in example 1.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As described in the background art, nitrogen-fixing microorganisms are of great significance for improving saline-alkali soil, and screening microorganisms with nitrogen-fixing activity as far as possible is of great significance for developing soil improvement preparations. Therefore, the invention provides Rhizobium roseum FN2, a microbial inoculum comprising the same and application thereof in the field of soil improvement.

Rhizobium rosettorum (Rhizobium rosettiformens) FN2 according to the first aspect has the 16S rDNA sequence shown in SEQ ID NO: 1.

The strain is separated from the rhizosphere saline-alkali soil of the common seepweed herb, the bacterial morphology of the strain meets the characteristics of rhizobia, and the strain is compared with known Rhizobium rosettiformens W3 through genome sequencing^TThe identity of the strain can reach more than 99 percent, and the strain is identified as Rhizobium lothii (Rhizobium rosettiformis) FN 2.

The morphological characteristics of Rhizobium rosette (Rhizobium rosettiformens) FN2 are as follows:

the characteristics of the thallus are as follows: the thallus is gram-negative bacilli, has no spores, and is arranged singly or in pairs. Is rod-shaped under an electron microscope and has a size of (1.5 to 3) μm x (0.6 to 1.0) μm

Colony characteristics: after 48h of culture on LB medium, the colonies were round and smooth.

The physiological and biochemical characteristics of Rhizobium rosette (Rhizobium rosettiformens) FN2 are as follows: can hydrolyze iron esculin citrate and 4-nitrobenzene-beta-D-galactopyranoside, and assimilate dextrose, L-arabinose, D-mannose, D-mannitol, N-acetyl glucosamine and D-maltose sodium citrate.

Preferably, the culture medium of Rhizobium rosette (Rhizobium rosettiformens) FN2 is LB culture medium or Ashby culture medium.

Further, the LB medium comprises tryptone, yeast extract 2.5g/L and sodium chloride.

Specifically, the LB liquid medium: 4-6 g/L of tryptone, 2-3 g/L of yeast extract, 4-6 g/L of sodium chloride and 0.8-1.2L of deionized water.

Specifically, the LB solid medium: 4-6 g/L, 2-3 g/L of yeast extract, 4-6 g/L of sodium chloride, 18-22 g/L of agar, 0.8-1.2L of deionized water, and pH value of 7.4.

Further, the Ashby azotobacter culture medium comprises potassium dihydrogen phosphate, magnesium sulfate heptahydrate, sodium chloride, calcium carbonate, mannitol, calcium sulfate dihydrate and water.

Specifically, in the liquid culture medium of the Ashby azotobacter, 0.1-0.3 g of monopotassium phosphate, 0.1-0.3 g of magnesium sulfate heptahydrate, 0.1-0.3 g of sodium chloride, 4-6 g of calcium carbonate, 9-11 g of mannitol, 0.05-0.15 g of calcium sulfate dihydrate, 0.8-1.2L of deionized water, and the pH value of 7-7.5.

Specifically, in the solid culture medium for the Ashby azotobacter, 0.1-0.3 g of monopotassium phosphate, 0.1-0.3 g of magnesium sulfate heptahydrate, 0.1-0.3 g of sodium chloride, 4-6 g of calcium carbonate, 9-11 g of mannitol, 0.05-0.15 g of calcium sulfate dihydrate, 0.8-1.2L of deionized water, pH 7-7.5 and 20g/L of agar are added.

The dosage form of the microbial inoculum is liquid microbial inoculum, powder or granules; further is a water suspending agent, a dispersible oil suspending agent, a wettable powder or a water dispersible granule.

Preferably, the microbial inoculum also comprises an agriculturally and pharmaceutically acceptable auxiliary material, and the agriculturally and pharmaceutically acceptable auxiliary material is selected from one or more of a dispersing agent, a wetting agent, a disintegrating agent, a binder, a defoaming agent, an antifreeze agent, a thickening agent, a filler and a solvent. The invention has no special limitation on the sources of the auxiliary materials acceptable in the agricultural pharmacy, and the like, and generally adopts the products sold in the market.

Preferably, the microbial inoculum can be any one of the following microbial inoculants 1) to 7):

1) a microbial inoculum for nitrogen fixation;

2) a microbial inoculum producing a nitrogenase;

3) a microbial inoculum for promoting plant growth;

4) improving the microbial inoculum for fertilizing soil;

5) a microbial inoculum for reducing the sensitivity of plants to stress;

6) a microbial inoculum for improving the stress resistance of plants;

7) a microbial inoculum for restoring soil ecology.

Preferably, the strain or the microbial inoculum is particularly suitable for saline-alkali soil in coastal saline areas, desert saline areas and grassland saline areas.

The specific application method comprises the following steps:

(1) directly mixing with saline-alkali soil: mixing the saline-alkali soil conditioner with saline-alkali soil in a weight ratio of 1-10%;

(2) seed dressing: before sowing seeds, the saline-alkali soil conditioner and the seeds are mixed in a proportion of 0.1-1% and sowed together.

Preferably, the soil conditioner also comprises a substance which has soil improvement activity, and the soil improvement activity comprises but is not limited to polysaccharides, alkali silicates, synthetic foams with open pores, humic acid type conditioners or salt inhibitors.

In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.

Example 1 screening and identification of saline-alkali tolerant azotobacter

1. Preparation of culture Medium

LB liquid medium: 5g/L of tryptone, 2.5g/L of yeast extract, 5g/L of sodium chloride and 1000mL of deionized water, wherein the pH value is 7.4.

LB solid medium: 5g/L of tryptone, 2.5g/L of yeast extract, 5g/L of sodium chloride, 20g/L of agar and 1000mL of deionized water, wherein the pH value is 7.4.

An Ashby azotobacter culture medium: 0.2g of monopotassium phosphate, 0.2g of magnesium sulfate heptahydrate, 0.2g of sodium chloride, 5g of calcium carbonate, 10g of mannitol, 0.1g of calcium sulfate dihydrate and 1000mL of deionized water, wherein the pH value is 7-7.5.

Ashby solid medium: 0.2g of monopotassium phosphate, 0.2g of magnesium sulfate heptahydrate, 0.2g of sodium chloride, 5g of calcium carbonate, 10g of mannitol, 0.1g of calcium sulfate dihydrate, 20g/L of agar and 1000mL of deionized water, wherein the pH value is 7-7.5.

2. Isolation and screening of azotobacteria

Weighing 10g of the saline-alkali soil at the rhizosphere of the Numbe Gaertn, putting the Numbe Gaertn saline-alkali soil into a 250mL conical flask containing 90mL of sterile water, soaking for 20min, and fully oscillating the conical flask containing the soil sample and the sterile glass beads on a constant-temperature oscillation incubator for 20min under the conditions of 30 ℃ and 160r/min to prepare soil suspension.

Using a pipette to aspirate 1mL of the suspension into a 15mL centrifuge tube containing 9mL of sterile water, which is then prepared to a concentration of 10^-3、10^-4、10^-5、10^-6、10^-7The soil dilution of (1).

Are respectively from 10^-3、10^-4、10^-5、10^-6、10^-7And (3) taking 100 mu L of soil diluent from the diluent, inoculating the soil diluent on an Ashby culture medium, and uniformly coating. Each soil dilution gradient was done in 3 replicates.

And (3) placing the coated flat plate in a constant-temperature incubator at 30 ℃ for inverted culture for 3-5 days, and carefully observing culture-mucus growing out around the dilute slurry on the culture medium. The mucus is initially colorless and transparent, then milky white and finally brown, indicating that the mucus contains the free living nitrogen-fixing bacteria. And after the thalli grow out, selecting a single colony, continuously carrying out streak purification on the Ashby solid culture medium, and purifying for more than 4 times until a pure culture is obtained.

And (3) inoculating the pure culture to an LB slant culture medium, culturing at 30 ℃ for 2-3 days, and storing in a refrigerator at 4 ℃ for later use. Inoculating the pure culture into LB liquid culture medium, culturing at 30 deg.C and 160r/min to logarithmic growth phase, mixing the bacterial suspension with 30% glycerol at a ratio of 1:1, and storing in-80 deg.C refrigerator.

3. Agrobacterium FN2 identification

(1) And (3) morphological identification:

inoculating pure culture into LB liquid culture medium, culturing at 30 deg.C and 160r/min to logarithmic growth phase, sucking 1mL of bacteria liquid with pipette gun into 15mL centrifuge tube containing 9mL sterile water, and sequentially preparing 10% concentration^-5、10^-6、10^-7The diluted solution of the microorganism of (1). Aspirate 100. mu.L of 10^-5、10^-6、10^-7The diluted gradient bacterial liquid is inoculated into LB solid culture medium, and the bacterial liquid is evenly coated on a flat plate by using a coater. Three replicates were run for each dilution gradient. Placing the flat plate in a constant-temperature incubator at 30 ℃ for culturing for 48h, and observing the growth condition and the colony characteristics of the strain; single colonies were picked and placed on clean slides, gram stained, and then the morphology and staining of cells were observed under an optical microscope.

The morphological identification result is as follows: the thallus is gram-negative bacilli, has no spores, and is arranged singly or in pairs. After 48h of culture on LB medium, the colonies were round and smooth (FIG. 1). The rod-like shape under an electron microscope and the size of the rod-like shape is (1.5 to 3) μm x (0.6 to 1.0) μm (FIG. 2).

(2) Physiological and biochemical characterization

The physiological and biochemical characteristics of the strain FN2 were determined according to the Manual of identification of conventional bacteria systems and API 20 NE.

Both catalase and oxidase were positive for strain FN 2. The results of the physiological and biochemical experiments are shown in Table 1.

TABLE 1 physiological and biochemical characterization of FN2 species

+: positive; -: negative of

(3)16S rDNA sequence analysis

Extracting the genome DNA of the strain by using a bacterial total DNA extraction reagent. Amplification was performed with bacterial 16S rDNA universal primers (27F: 5'-AGAGTTTGATCCTGGCTCAG-3' and 1492R: 5'-GGTTACCTTGTTACGACTT-3'). A100. mu.L 16S rDNA reaction was used: taq (5U/. mu.L) 0.8. mu.L; 10 × PCR Buffer (Mg)²⁺Plus) 10. mu.L; dNTP mix (2.5mM/each) 8. mu.L; 2.5ng of template DNA; 2. mu.L of primer F1 (10. mu. mol/L) and 2. mu.L of primer R1 (10. mu. mol/L); ddH₂O make up to 100. mu.L. The reaction condition is 95 ℃ for 5 min; 30 cycles of 95 ℃ for 1min, 57 ℃ for 1min, and 72 ℃ for 1min and 20 sec; finally, extension is carried out for 5min at 72 ℃. After sequencing of the PCR products, similarity search and homology alignment were performed using BLAST, sequence alignment analysis was performed using Clustal X2.0, and the 16S rDNA phylogenetic tree of FN2 was revealed using MEGA7 software orthotopic ligation (FIG. 3).

The result of the identification is rhizobium rosette.

Example 2 test of salinity and alkalinity tolerance of Azotobacter FN2

1. Preparation of solutions

Preparation of saline-alkali solutions with different gradients: setting salinity at 0.1g/L, 0.5g/L, 1.0g/L, 1.5g/L, 3.0g/L, setting alkalinity at 7.2, 7.6, 8.0, 8.4, and treating for 20 times. The salinity is configured by sodium chloride, and the alkalinity is adjusted by hydrochloric acid and sodium hydroxide.

The preparation of the LB liquid culture medium without salinity: 5g/L of tryptone, 2.5g/L of yeast extract, 1000mL of deionized water and natural pH.

2. FN2 growth curve determination under different salinity

Inoculating strain FN2 into liquid LB medium, and culturing until OD is 0.1 (bacterial density)Degree of about 10⁸one/mL), and storing in a refrigerator at 4 ℃ for later use.

The bacterial solution with OD 1.0 was inoculated into a medium of different salinity and alkalinity containing 10% LB without salinity and the absorbance was measured every two hours at a wavelength of 600nm, at an inoculation amount of 5%.

The result shows that the azotobacter FN2 has strong saline-alkali resistance. At the conditions of pH 7.2, 7.6 and 8.0 and salinity of 1.0g/L, FN2 grows fastest, and the maximum specific growth rates are 0.04546/h, 0.04462/h and 0.03442/h respectively, and are better than those in the environment with lower salinity level under the same alkalinity. At pH 8.4, FN2 reached the maximum specific growth rate (0.01839/h) and maximum biomass (OD600 ═ 0.3976) at salinity of 3.0 g/L.

Example 3 Germination experiments on maize inoculated with Azotobacter FN2

Selecting corn seeds with round and smooth grains and full seeds, soaking the corn seeds in 70% absolute ethyl alcohol for 2min for disinfection, and then washing the corn seeds clean with tap water. Salinity gradient of 0.1g/L, 0.5g/L, 1.0g/L, 1.5g/L, 3.0g/L, alkalinity gradient of 7.2, 7.6, 8.0, 8.4, total 20 treatments. Each culture dish is covered with filter paper, after 10 corn seeds are sown, 10 corn seeds are inoculated⁹FN2 strain, and adding water with same volume and different saline-alkali gradients. Two of each saline-alkali gradient are arranged in parallel. The strain is a strain of Azospirillum brasilense (Azospirillum brasilense) purchased from China general microbiological culture Collection center (CGMCC) and having the same nitrogen fixing ability. And observing the germination condition of the corn seeds after one week.

The result shows that the germination rate of the corn seeds inoculated with FN2 can reach more than 80% under the condition of any alkalinity and salinity of 3.0g/L, and the germination rate of the corn seeds inoculated with Azospirillum brasilense does not exceed 50% under the same alkalinity and salinity environment. This indicates that corn seeds inoculated with FN2 were more able to promote germination under higher salinity conditions.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

SEQUENCE LISTING

<110> Shandong university

<120> Rhizobium loti FN2, microbial inoculum thereof and application thereof in soil improvement field

<130> 2010

<160> 1

<170> PatentIn version 3.3

<210> 1

<211> 1368

<212> DNA

<213> Rhizobium rosettfumans (Rhizobium rosettiformens) FN2

<400> 1

gcttacacat gcaagtcgag cgccccgcaa ggggagcggc agacgggtga gtaacgcgtg 60

ggaatctacc gtgccctacg gaatagctcc gggaaactgg aattaatacc gtatacgccc 120

tacgggggaa agatttatcg gggtatgatg agcccgcgtt ggattagcta gttggtgggg 180

taaaggccta ccaaggcgac gatccatagc tggtctgaga ggatgatcag ccacattggg 240

actgagacac ggcccaaact cctacgggag gcagcagtgg ggaatattgg acaatgggcg 300

caagcctgat ccagccatgc cgcgtgagtg atgaaggtct taggattgta aagctctttc 360

accggtgaag ataatgacgg taaccggaga agaagccccg gctaacttcg tgccagcagc 420

cgcggtaata cgaagggggc tagcgttgtt cggaattact gggcgtaaag cgcacgtagg 480

cggatattta agtcaggggt gaaatcccag agctcaactc tggaactgcc tttgatactg 540

ggtatcttga gtatggaaga ggtgagtgga attccgagtg tagaggtgaa attcgtagat 600

attcggagga acaccagtgg cgaaggcggc tcactggtcc attactgacg ctgaggtgcg 660

aaagcgtggg gagcaaacag gattagatac cctggtagtc cacgccgtaa acgatgaatg 720

ttagccgtcg ggcagtatac tgttcggtgg cgcagctaac gcattaaaca ttccgcctgg 780

ggagtacggt cgcaagatta aaactcaaag gaattgacgg gggcccgcac aagcggtgga 840

gcatgtggtt taattcgaag caacgcgcag aaccttacca gctcttgaca tccgggtcgc 900

ggacagtgga gacattgtcc ttcagttagg ctggacccag gacaggtgct gcatggctgt 960

cgtcagctcg tgtcgtgaga tgttgggtta agtcccgcaa cgagcgcaac cctcgccctt 1020

agttgccagc attcagttgg gcactctaag gggactgccg gtgataagcc gagaggaagg 1080

tggggatgac gtcaagtcct catggccctt acgggctggg ctacacacgt gctacaatgg 1140

tggtgacagt gggcagcgag acggtgacgt cgagctaatc tccaaaagcc atctcagttc 1200

ggattgcact ctgcaactcg agtgcatgaa gttggaatcg ctagtaatcg cggatcagca 1260

tgccgcggtg aatacgttcc cgggccttgt acacaccgcc cgtcacacca tgggagttgg 1320

ttttacccga aggtagtgcg ctaacccgca agggaggcag ctaaccac 1368

Claims

1. Rhizobium rosette (A)Rhizobium rosettiformans) FN2, wherein the strain has been deposited in China general microbiological culture Collection center (CGMCC), China general microbiological culture Collection center, CGMCC, at 12 months and 7 days 2020: the biological preservation number of the Xilu No. 1 Hospital No. 3 of the Chaojing Chaoyang district is: CGMCC number 21307.

2. A microbial preparation comprising the rhizobium rosenbergii strain of claim 1 (A), (B), (C), and (C)Rhizobium rosettiformans）FN2。

3. The microbial inoculum according to claim 2, which is in the form of liquid microbial inoculum, powder or granules.

4. The microbial inoculum of claim 3, which is an aqueous suspension, a dispersible oil suspension, a wettable powder or a water dispersible granule.

5. The microbial inoculum of claim 3, further comprising an agriculturally pharmaceutically acceptable adjuvant, wherein the agriculturally pharmaceutically acceptable adjuvant is selected from one or more of a dispersing agent, a wetting agent, a disintegrating agent, a binder, an antifoaming agent, an antifreeze agent, a thickener, a filler and a solvent.

6. The microbial inoculum according to claim 3, which can be any one of the following 1) to 5):

1) a microbial inoculum for nitrogen fixation;

2) a microbial inoculum producing a nitrogenase;

3) a microbial inoculum for promoting plant growth;

4) improving the microbial inoculum for fertilizing soil;

5) a microbial inoculum for restoring soil ecology.

7. Rhizobium rosenbergii of claim 1 (a), (b), (c), (d) and d), (d) and (d)Rhizobium rosettiformans) FN2 and the microbial inoculum of any one of claims 2 to 6 in the field of soil improvement.

8. The use according to claim 7, wherein the strain or inoculum is used in saline-alkali soil of the type of coastal saline areas, desert saline areas and grassland saline areas.

9. A soil conditioner characterized in that said soil conditioner comprises the sithizobium rosette of claim 1 (A)Rhizobium rosettiformans）FN2。

10. A soil conditioner characterized in that the soil conditioner comprises the microbial inoculum according to any one of claims 2 to 6.

11. A soil amendment according to any of claims 9 to 10, further comprising other materials having soil amendment activity, said soil amendment activity comprising polysaccharides, alkali silicates, open-celled synthetic foams, humic acid amendments or salt suppressors.