CN112625960A

CN112625960A - Agrobacterium DP3, microbial inoculum thereof and application thereof in field of biological fertilizer preparation

Info

Publication number: CN112625960A
Application number: CN202011584465.8A
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: 2020-12-28
Filing date: 2020-12-28
Publication date: 2021-04-09
Anticipated expiration: 2040-12-28
Also published as: CN112625960B

Abstract

The invention particularly relates to agrobacterium tumefaciens DP3, a microbial inoculum thereof and application thereof in the field of preparation of biofertilizer. The phosphorus-dissolving bacteria can convert insoluble phosphate into soluble phosphorus, can be used for improving the microenvironment of saline-alkali soil, improving the utilization rate of phosphorus in soil and promoting the growth of crops. The invention aims to screen a novel strain for improving the survival rate of saline-alkali soil crops, and provides Agrobacterium sp (Agrobacterium sp) DP3, wherein the strain has good effects of salt resistance, phosphorus dissolution and crop growth promotion, and has good effects when being applied to biological bacterial fertilizers and soil conditioners.

Description

Agrobacterium DP3, microbial inoculum thereof and application thereof in field of biological fertilizer preparation

Technical Field

The invention belongs to the technical field of soil improvement engineering strains, and particularly relates to Agrobacterium sp (Agrobacterium sp) DP3, a microbial inoculum thereof and application thereof in the field of biofertilizer.

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.

According to the reports of Food and Agricultural Organization (FAO) and textbook organization (UNESCO) of the United nations, the area of the saline-alkali soil in the world is as high as 9.5438 multiplied by 10⁸hm²Soil salinization is a global environmental problem. It is estimated that the worldwide saline-alkali land is 1.0 × 10 annually⁶～1.5×10⁶hm²Is increasing. Salinization not only destroys 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.

Phosphorus (P) is one of the essential macronutrients for plant growth and development, and plays an important role in the generation-based transmission of many important functions including energy metabolism, structural function, signal transduction function, and genetic characteristics. The total phosphorus content of soil in China is high, but the effective phosphorus content which can be directly absorbed and utilized by plants is generally not more than 5 percent of the total phosphorus content, and most of phosphorus fertilizers and Ca in the soil²⁺、Fe³⁺、Fe²⁺、Al³⁺And the combination of the two components forms insoluble phosphate which cannot be directly absorbed and utilized by plants, so that phosphorus becomes a main factor for restricting the production of crops.

Phosphate solubilizing bacteria, also known as phosphate solubilizing bacteria, convert insoluble phosphates to soluble phosphorus. Such as Bacillus (Bacillus), Pseudomonas (Pseudomonas), Salmonella (Salmonella), Chromobacterium (Clomobacterium), Escherichia (Escherichia), Agrobacterium (Agrobacterium), etc., belong to the genus of phosphate solubilizing bacteria. The phosphate solubilizing bacteria are added into the saline-alkali soil, so that the microenvironment of the saline-alkali soil can be improved, the utilization rate of phosphorus in the soil can be improved, and the growth of crops can be promoted. Therefore, the research and application of the salt-tolerant phosphate solubilizing bacteria can improve the quality of saline-alkali soil, adjust the ecological balance of microorganisms in the soil and be beneficial to the sustainable development of agriculture.

Disclosure of Invention

Based on the above research background, the present invention aims to provide a novel strain for increasing the survival rate of saline-alkali soil crops. In order to achieve the purpose, the invention screens the rhizosphere soil of suaeda salsa in the delta area of the east-Ying yellow river to obtain a strain of Agrobacterium tumefaciens (Agrobacterium sp) DP3, and the strain is identified by morphological characteristics, physiological and biochemical characteristics and 16S rDNA sequence analysis to determine the salt tolerance and phosphorus dissolving capacity of the strain and the actual application condition of saline-alkali soil, so that strain resources are provided for improving the utilization rate of phosphorus in the saline-alkali soil.

Based on the above research, the first aspect of the present invention provides an Agrobacterium sp DP3, which has been deposited in the common microorganism center of the national culture collection and management committee for microorganisms of CGMCC at 12/7/2020 with the addresses of: the biological preservation number of the Xilu No. 1 Hospital No. 3 of the Chaojing Chaoyang district is: CGMCC No. 21306.

In a second aspect of the invention, there is provided a microbial inoculum comprising Agrobacterium sp 3 according to the first aspect and/or a culture thereof.

In a third aspect of the invention, the application of the bacterial strain of the first aspect and the microbial inoculum of the second aspect in the field of preparation of biological fertilizers is provided.

In a fourth aspect of the present invention, there is provided a biological fertilizer comprising the Agrobacterium sp 3 of the first aspect and/or the microbial inoculum of the second aspect.

In a fifth aspect of the invention, a soil conditioner is provided, wherein the soil conditioner comprises and/or uses the biological fertilizer of the fourth aspect.

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

the phosphorus-dissolving bacterium DP3 provided by the invention has good salt tolerance and phosphorus-dissolving capacity, can be used for promoting the growth of crops in saline-alkali soil, and provides strain resources for improving the utilization rate of phosphorus in the 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 photograph showing a colony of Agrobacterium (Agrobacterium sp.) DP3 described in example 1;

FIG. 2 is an electron micrograph of a bacterial cell of Agrobacterium (Agrobacterium sp.) DP3 according to example 1;

FIG. 3 is a tree diagram of the 16S rDNA phylogenetic tree of DP3 described 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 introduced in the background art, the phosphate solubilizing bacteria can convert insoluble phosphate in soil into soluble phosphate so as to be more easily applied to crops, and further play a role in promoting the growth of the crops. The efficient phosphorus-solubilizing bacteria screened as much as possible have important significance for improving saline-alkali soil and growing crops. Therefore, the invention provides an Agrobacterium sp (Agrobacterium sp) DP3 strain, a microbial inoculum comprising the strain and application of the strain in the field of soil improvement.

The Agrobacterium sp DP3 of 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 identified as Agrobacterium by genome sequencing comparison and is named as Agrobacterium (Agrobacterium sp) DP 3.

The morphological characteristics of the Agrobacterium (Agrobacterium sp.) DP3 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. The rod-shaped material is rod-shaped under an electron microscope, and has a size of (1.5 to 0.3) 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 the Agrobacterium (Agrobacterium sp.) DP3 are as follows: can utilize potassium nitrate and urea in the substrate, hydrolyze the esculin ferric citrate and the 4-nitrobenzene-beta-D-galactopyranoside, and assimilate dextrose, L-arabinose, D-mannose, D-mannitol, N-acetyl glucosamine, D-maltose, potassium gluconate and malic acid.

Preferably, the medium of the Agrobacterium (Agrobacterium sp.) DP3 is LB medium or PKO 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 PKO culture medium comprises glucose, tricalcium phosphate, ammonium sulfate, sodium chloride, potassium chloride, magnesium sulfate heptahydrate, manganese sulfate, ferrous sulfate and yeast powder.

Specifically, in the PKO liquid culture medium, 8-11 g/L of glucose, 4-6 g/L of tricalcium phosphate, 0.4-0.6 g/L of ammonium sulfate, 0.15-0.25 g/L of sodium chloride, 0.15-0.25 g/L of potassium chloride, 0.2-0.4 g/L of magnesium sulfate heptahydrate, 0.02-0.05 g/L of manganese sulfate, 0.002-0.005 g/L of ferrous sulfate, 0.4-0.6 g/L of yeast powder, 0.9-1.1L of distilled water, 7.0 +/-0.2 of pH, and high-temperature and high-pressure sterilization.

Specifically, in the PKO solid culture medium, 8-11 g/L of glucose, 4-6 g/L of tricalcium phosphate, 0.4-0.6 g/L of ammonium sulfate, 0.15-0.25 g/L of sodium chloride, 0.15-0.25 g/L of potassium chloride, 0.2-0.4 g/L of magnesium sulfate heptahydrate, 0.02-0.05 g/L of manganese sulfate, 0.002-0.005 g/L of ferrous sulfate, 0.4-0.6 g/L of yeast powder, 0.9-1.1L of distilled water, 20g/L of agar, pH of 7.0 +/-0.2, and high-temperature and high-pressure sterilization.

In a second aspect of the invention there is provided a microbial inoculum comprising a culture of Agrobacterium (Agrobacterium sp.) DP3 and/or a bacterium according to the first aspect.

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 6):

1) a microbial inoculum for dissolving phosphorus;

2) a microbial inoculum for promoting plant growth;

3) improving the microbial inoculum for fertilizing soil;

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

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

6) a microbial inoculum for restoring soil ecology.

Preferably, the biofertilizer is used in a manner including, but not limited to, direct application to soil or treatment of crop seeds.

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 phosphate solubilizing halotolerant bacteria

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.

PKO liquid medium: 10g/L of glucose, 5g/L of tricalcium phosphate, 0.5g/L of ammonium sulfate, 0.2g/L of sodium chloride, 0.2g/L of potassium chloride, 0.3g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate, 0.003g/L of ferrous sulfate, 0.5g/L of yeast powder and 1000mL of distilled water, wherein the pH value is 7.0 +/-0.2, and the mixture is sterilized at the high temperature and the high pressure of 121 ℃ for 30 min.

PKO liquid medium: 10g/L of glucose, 5g/L of tricalcium phosphate, 0.5g/L of ammonium sulfate, 0.2g/L of sodium chloride, 0.2g/L of potassium chloride, 0.3g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate, 0.003g/L of ferrous sulfate, 0.5g/L of yeast powder, 1000mL of distilled water, 20g/L of agar, 7.0 +/-0.2 of pH, and sterilizing at 121 ℃ for 30min under high temperature and high pressure.

2. Separation and screening of phosphate solubilizing bacteria

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 a PKO culture medium, and uniformly coating. Each soil dilution gradient was done in 3 replicates.

And (3) putting the coated flat plate into a constant-temperature incubator at 30 ℃ for inverted culture for 3-5 d, picking a single bacterial colony with a large transparent ring at the periphery (the bacterial colony with the transparent ring is regarded as a bacterial colony with phosphorus dissolving activity) after the thalli grow out, continuously carrying out streak purification on a PKO 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. Identification of Agrobacterium DP3

(1) And (3) morphological identification:

inoculating pure culture into LB liquid culture medium at 30 deg.CCulturing at 160r/min until the logarithmic growth phase, sucking 1mL of bacteria liquid into a 15mL centrifuge tube containing 9mL of sterile water by using a pipette gun, and preparing the bacteria liquid with the concentration of 10 in sequence^-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 bacteria, has no spore, and is arranged singly or in pairs. After 48h of culture on LB medium, the colonies were round and smooth (FIG. 1). The rod-shaped material is rod-shaped under an electron microscope, and has a size of (1.5 to 0.3) μm x (0.6 to 1.0) μm (FIG. 2).

(2) Physiological and biochemical characterization

The physiological and biochemical characteristics of the strain DP3 are determined according to the Manual of identification of conventional bacterial systems and the API 20NE specification.

Both catalase and oxidase of strain DP3 were positive. The results of the physiological and biochemical experiments are shown in Table 1.

TABLE 1 physiological and biochemical characterization of DP3 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'). Using 100. mu.L of 16S rDNA reactionThe method comprises the following steps: 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 in total at 95 ℃ for 1min, 57 ℃ for 1min, and 72 ℃ for 1min for 20 sec; finally, extension is carried out for 5min at 72 ℃. After sequencing the PCR products were subjected to similarity search and homology alignment using BLAST, sequence alignment analysis using Clustal X2.0, and the 16S rDNA phylogenetic tree of DP3 was shown using MEGA7 software orthotopic ligation (FIG. 3).

The result of the identification was Agrobacterium.

EXAMPLE 2 experiment of salt and alkali tolerance of phosphate solubilizing bacteria

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. Measurement of growth curve of DP3 under different salinity

The strain DP3 was inoculated into liquid LB medium and cultured until OD was 0.1 (density of about 10. ang.)⁸one/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 phosphate solubilizing bacteria DP3 have stronger saline-alkali resistance. The DP3 reached the highest density of bacteria at salinity of 1.0g/L at pH 7.2 and 7.6, and the maximum absorbance reached 0.603 and 0.622, respectively. At a pH of 8.4, DP3 reached a maximum specific growth rate at a salinity of 3.0g/L, the maximum specific growth rate being 0.02651/h.

Example 3 germination experiments on maize inoculated with P.lysing bacteria DP3

Selecting large, mellow and full-grain cornSoaking the seeds in 70% absolute ethyl alcohol for 2min for disinfection, and washing with tap water. Each culture dish is coated with filter paper, sowed with 10 corn seeds and inoculated with 10 corn seeds⁹And (3) carrying out DP3 bacteria, and irrigating with water with different saline-alkali gradients. 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. Two of each saline-alkali gradient are arranged in parallel. Bacillus megaterium (Bacillus megaterium) purchased from China general microbiological culture Collection center (CGMCC) and having the same phosphorus dissolving capacity is used as a reference. 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 DP3 can reach more than 70% when the salinity and the alkalinity are 3.0g/L, and the germination rate of the corn seeds inoculated with Bacillus megaterium does not exceed 40% under the same salinity and alkalinity environment. This indicates that the DP3 inoculated corn seeds are more able to promote germination of corn seeds 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> agrobacterium tumefaciens DP3, microbial inoculum thereof and application thereof in field of biological fertilizer preparation

<130> 2010

<160> 1

<170> PatentIn version 3.3

<210> 1

<211> 1366

<212> DNA

<213> Agrobacterium sp DP 316S rDNA

<400> 1

gcttacacat gcaagtcgag cgccccgcaa ggggagcggc agacgggtga gtaacgcgtg 60

ggaatctacc gagccctgcg gaatagctcc gggaaactgg aattaatacc gcatacgccc 120

tacgggggaa agatttatcg gggtttgatg agcccgcgtt ggattagcta gttggtgggg 180

taaaggccta ccaaggcgac gatccatagc tggtctgaga ggatgatcag ccacattggg 240

actgagacac ggcccaaact cctacgggag gcagcagtgg ggaatattgg acaatgggcg 300

caagcctgat ccagccatgc cgcgtgagtg atgaaggccc tagggttgta aagctctttc 360

aacggtgaag ataatgacgg taaccgtaga agaagccccg gctaacttcg tgccagcagc 420

cgcggtaata cgaagggggc tagcgttgtt cggaattact gggcgtaaag cgcacgtagg 480

cggatattta agtcaggggt gaaatcccgg ggctcaacct cggaactgcc tttgatactg 540

ggtatcttga gtatggaaga ggtaagtgga attgcgagtg tagaggtgaa attcgtagat 600

attcgcagga acaccagtgg cgaaggcggc ttactggtcc 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 ttcggggtat 900

gggcagtgga gacattgtcc ttcagttagg ctggccccag aacaggtgct gcatggctgt 960

cgtcagctcg tgtcgtgaga tgttgggtta agtcccgcaa cgagcgcaac cctcgccctt 1020

agttgccagc atttagttgg gcactctaag gggactgccg gtgataagcc gagaggaagg 1080

tggggatgac gtcaagtcct catggccctt acgggctggg ctacacacgt gctacaatgg 1140

tggtgacagt gggcagcgag acagcgatgt cgagctaatc tccaaaagcc atctcagttc 1200

ggattgcact ctgcaactcg agtgcatgaa gttggaatcg ctagtaatcg cagatcagca 1260

tgctgcggtg aatacgttcc cgggccttgt acacaccgcc cgtcacacca tgggagttgg 1320

ttttacccga aggtagtgcg ctaaccgcaa ggaggcagct aaccac 1366

Claims

1. An Agrobacterium (Agrobacterium sp.) DP3, wherein the strain has been deposited in the national common microorganism center of the national microorganism culture collection management committee (CGMCC) at 12/7/2020 with the addresses of: the biological preservation number of the Xilu No. 1 Hospital No. 3 of the Chaojing Chaoyang district is: CGMCC No. 21306.

2. The Agrobacterium sp DP3 of claim 1, wherein the Agrobacterium sp DP3 has the 16S rDNA sequence of SEQ ID No. 1.

3. The Agrobacterium (Agrobacterium sp.) DP3 according to claim 1, wherein the Agrobacterium (Agrobacterium sp.) DP3 has the following morphological characteristics:

the characteristics of the thallus are as follows: the thallus is gram-negative bacilli, has no spores, and is arranged singly or in pairs. Rod-shaped under an electron microscope, and the size of the rod-shaped is (1.5-0.3) mum x (0.6-1.0) mum;

4. The Agrobacterium (Agrobacterium sp.) DP3 according to claim 1, wherein the physiological and biochemical characteristics of Agrobacterium (Agrobacterium sp.) DP3 are as follows: can utilize potassium nitrate and urea in the substrate, hydrolyze the esculin ferric citrate and the 4-nitrobenzene-beta-D-galactopyranoside, and assimilate dextrose, L-arabinose, D-mannose, D-mannitol, N-acetyl glucosamine, D-maltose, potassium gluconate and malic acid.

5. The Agrobacterium (Agrobacterium sp.) DP3 according to claim 1, wherein the medium of Agrobacterium (Agrobacterium sp.) DP3 is LB medium or PKO medium;

preferably, the LB culture medium comprises tryptone, yeast extract and sodium chloride;

further, 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;

or, 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.

6. The Agrobacterium (Agrobacterium sp.) DP3 of claim 1, wherein the PKO medium comprises glucose, tricalcium phosphate, ammonium sulfate, sodium chloride, potassium chloride, magnesium sulfate heptahydrate, manganese sulfate, ferrous sulfate, and yeast powder;

preferably, in the PKO liquid culture medium, 8-11 g/L of glucose, 4-6 g/L of tricalcium phosphate, 0.4-0.6 g/L of ammonium sulfate, 0.15-0.25 g/L of sodium chloride, 0.15-0.25 g/L of potassium chloride, 0.2-0.4 g/L of magnesium sulfate heptahydrate, 0.02-0.05 g/L of manganese sulfate, 0.002-0.005 g/L of ferrous sulfate, 0.4-0.6 g/L of yeast powder, 0.9-1.1L of distilled water, 7.0 +/-0.2 of pH, and high-temperature and high-pressure sterilization;

or in the PKO solid culture medium, 8-11 g/L of glucose, 4-6 g/L of tricalcium phosphate, 0.4-0.6 g/L of ammonium sulfate, 0.15-0.25 g/L of sodium chloride, 0.15-0.25 g/L of potassium chloride, 0.2-0.4 g/L of magnesium sulfate heptahydrate, 0.02-0.05 g/L of manganese sulfate, 0.002-0.005 g/L of ferrous sulfate, 0.4-0.6 g/L of yeast powder, 0.9-1.1L of distilled water, 20g/L of agar, pH of 7.0 +/-0.2, and high-temperature and high-pressure sterilization.

7. A bacterial preparation comprising a culture of Agrobacterium (Agrobacterium sp.) DP3 and/or a bacterium according to any one of claims 1-6;

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

preferably, the microbial inoculum also comprises an auxiliary material acceptable in the pesticide, and the auxiliary material acceptable in the pesticide 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;

1) a microbial inoculum for dissolving phosphorus;

2) a microbial inoculum for promoting plant growth;

3) improving the microbial inoculum for fertilizing soil;

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

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

6) a microbial inoculum for restoring soil ecology.

8. Use of the Agrobacterium (Agrobacterium sp.) DP3 according to any one of claims 1 to 6 or the microbial inoculum according to claim 7 in the field of preparation of biofertilizers;

9. A biological fertilizer, characterized in that it comprises an Agrobacterium sp DP3 according to any one of claims 1 to 6, an agent according to claim 7.

10. A soil amendment characterized in that the soil amendment includes and/or is a biofertilizer according to claim 9;