Plant growth-promoting rhizobacteria capable of effectively improving growth amount of alfalfa and application of plant growth-promoting rhizobacteria

Abstract

The invention belongs to the technical field of application of agricultural microorganisms, and relates to a plant growth-promoting rhizobacteria capable of effectively increasing the growth amount of alfalfa and application of the plant growth-promoting rhizobacteria, and the plant growth-promoting rhizobacteria is Burkholderia sp. MCWP-A3-15. The Burkholderia sp. MCWP-A3-15 is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number of the Burkholderia sp. MCWP-A3-15 is CGMCC No.31562. The Burkholderia sp. The burkholderia disclosed by the invention can promote the growth of alfalfa, increase the yield of alfalfa, improve the physical and chemical properties of soil and increase the fertility of the soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of the application of agricultural microorganisms, and is mainly an invention directed to plant growth-promoting rhizobacteria, specifically involving Burkholderia and the use thereof to regulate the growth of alfalfa and improve the physical and chemical properties of soil. Background Art

[0002] Inner Mongolia Autonomous Region is one of the main alfalfa production bases in China. With the development of modern animal husbandry, strong support from national policies, and the rapid development of the dairy farming industry, alfalfa has gradually become an irreplaceable forage grass. However, although alfalfa is a salt-tolerant crop, as the degree of soil salinization increases, the content of directly available nutrient elements in the soil is greatly reduced, still unable to meet its growth requirements. Plant growth-promoting rhizobacteria can promote plant growth under salt stress through different action mechanisms. Therefore, screening and identifying plant growth-promoting rhizobacteria in Inner Mongolia region has great development potential and research value for maintaining soil productivity and promoting plant growth.

[0003] Growth-promoting rhizobacteria can greatly improve the nutrient acquisition efficiency of alfalfa. On the one hand, some bacteria have the ability to fix nitrogen. For example, Rhizobium meliloti, which invades the alfalfa root system to form root nodules and converts nitrogen in the air into ammonia nitrogen that can be utilized by plants, providing a stable and inexpensive nitrogen source for alfalfa growth and strongly promoting the lush growth of plant stems and leaves, which is one of the key factors for high alfalfa yield. On the other hand, many growth-promoting bacteria can secrete organic acids, such as oxalic acid, citric acid, etc. These acid substances can dissolve insoluble phosphorus and potassium minerals in the soil, releasing phosphorus and potassium elements for alfalfa to absorb. Sufficient phosphorus promotes the development of alfalfa roots, enhances stress resistance, and is also beneficial for flower bud differentiation and seed formation; potassium element ensures the thickening of plant stems, improves the photosynthesis efficiency, and reduces the risk of lodging. The two work together to help improve alfalfa yield. In the face of adverse environments such as drought, high temperature, and salinity, growth-promoting rhizobacteria help alfalfa grow tenaciously. When facing drought, growth-promoting bacteria prompt alfalfa to synthesize more osmotic adjustment substances such as proline and betaine, reduce the osmotic pressure inside cells, help the plant absorb water from the dry soil as much as possible, maintain cell turgor pressure, ensure the normal progress of physiological processes such as photosynthesis, avoid growth stagnation or even death due to drought, and maintain stable yield. In saline-alkali soil, growth-promoting rhizobacteria regulate the pH of rhizosphere soil by secreting special substances, reduce the toxicity of salinity and alkalinity to alfalfa roots, and at the same time enhance the root system's ability to repel salts, enabling alfalfa to take root and grow on saline-alkali land, expanding the planting range of alfalfa and indirectly opening up new ways to increase the total yield. In summary, growth-promoting rhizobacteria act on the growth and development of alfalfa in all aspects, from nutrient supply, hormone regulation, disease defense to stress resistance assistance, and have an important promoting effect on alfalfa yield improvement. Reasonable utilization of growth-promoting rhizobacteria is expected to become a key strategy for high-yield cultivation of alfalfa. Summary of the Invention

[0004] The object of the present invention is to provide a strain of Burkholderia MCWP-A3-15. The strain provided by the present invention was collected from the Leymus chinensis and alfalfa planting areas in Inner Mongolia. First, rhizosphere soil was dug from the Leymus chinensis and alfalfa planting areas for isolation, purification, and 16S rDNA identification and classification. Then, preliminary screening was carried out indoors and field re-screening was carried out. By measuring indicators such as the plant height, root length, aboveground biomass of alfalfa after inoculation, and soil physical and chemical properties, strains with obvious yield-increasing effects on alfalfa were analyzed and screened to provide a basis for the high-yield cultivation of alfalfa.

[0005] The object of the present invention is achieved by the following technical solutions: The present invention provides a plant growth-promoting rhizobacterium that can effectively increase the growth of alfalfa. The growth-promoting rhizobacterium is Burkholderia MCWP-A3-15.

[0006] The Burkholderia MCWP-A3-15 ( Burkholderia sp. ) is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the deposit number CGMCC No. 31562, the deposit date being August 12, 2024, and the deposit address being No. 3, Yard 1, Beichen Road, Chaoyang District, Beijing.

[0007] The present invention also provides the application of the Burkholderia MCWP-A3-15 in promoting the growth of alfalfa. The Burkholderia MCWP-A3-15 can increase the plant height, root length, and dry weight per plant of alfalfa.

[0008] The present invention also provides the application of the Burkholderia MCWP-A3-15 in increasing the yield of alfalfa.

[0009] The present invention also provides the application of the Burkholderia MCWP-A3-15 in improving soil physical and chemical properties. The physical and chemical properties include total nitrogen content and available phosphorus content.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. The plant growth-promoting rhizobacterium strain of the present invention is an indigenous growth-promoting rhizobacterium collected and isolated from the Leymus chinensis and alfalfa planting areas in eastern Inner Mongolia, with low cost and no pollution.

[0011] 2. Through the screening and identification of plant growth-promoting rhizobacteria and the verification of pot and field experiments, the Burkholderia can effectively increase the growth of alfalfa.

[0012] 3. The strain obtained by the present invention can effectively improve soil physical and chemical properties.

[0013] In summary, the Burkholderia MCWP-A3-15 provided by the present invention can promote the growth of alfalfa, increase the yield of alfalfa, and can improve soil physical and chemical properties, significantly increase the content of nitrogen, phosphorus, and potassium in the soil, and increase soil fertility. Description of the Drawings

[0014] Figure 1 : Neighbor-joining phylogenetic tree of the 16S rDNA gene sequence of Burkholderia sp. MCWP-A3-15

[0015] Figure 2 : Effects of inoculating different plant growth-promoting rhizobacteria (PGPR) strains on the plant height and root length of alfalfa under sterile conditions

[0016] Figure 3 : Effects of inoculating different PGPR strains on the dry weight per plant of alfalfa under sterile conditions

[0017] Figure 4 : Effects of inoculating different PGPR on the plant height and root length of alfalfa in the field

[0018] Figure 5 : Effects of inoculating different PGPR on the dry weight per plant of alfalfa in the field

[0019] Figure 6 : Effects of PGPR on soil pH value

[0020] Figure 7 : Effects of PGPR on soil organic matter content

[0021] Figure 8 : Effects of PGPR on soil total nitrogen content

[0022] Figure 9 : Effects of PGPR on soil available phosphorus content

[0023] In the figure, abcde represent significant differences at P the 0.05 level Detailed Description of the Invention

[0024] To make the objectives and advantages of the present invention clearer, the following describes the specific implementation manners of the present invention in detail in combination with embodiments. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are all conventional methods

[0025] Example 1. Isolation, screening and identification of strains

[0026] 1. Sample collection

[0027] Rhizosphere soil samples of plants were collected from alfalfa and Leymus chinensis planting areas in eastern Inner Mongolia. At the early flowering stage of the plants, the 5-point sampling method was used. Select tall, healthy plants, remove the above-ground parts of the plants, put the roots together with the rhizosphere soil into sterile bags, and place them in a foam box equipped with ice packs. The samples were processed within 24 hours

[0028] 2. Isolation of strains

[0029] Bring the rhizosphere soil of plants back to the laboratory, gently shake off the soil attached to the roots, weigh 10 g of the roots with a small amount of soil attached and put them into a triangular flask containing 90 mL of sterile normal saline. Put 5 sterilized glass beads in the flask, shake on a shaker for 30 min (180 r / min), and then let it stand for 10 min. Next, prepare a sterilized test tube and add 9 mL of normal saline to it, and add 1 mL of the soil suspension to it to prepare a 10 -2 soil gradient dilution; then pipette 1 mL of the suspension from the test tube in the previous step into another 9 mL test tube of the same kind, and repeat this process to prepare 10 -3 、10 -4 and 10 -5 gradient dilutions in sequence.

[0030] Apply the prepared gradient dilutions onto the LB solid medium and streak it 3 times, incubate at 37 °C for 24 h, and select single colonies with obvious differences in colony morphology for further screening.

[0031] Preparation of LB solid medium: Dissolve 5 g of yeast extract, 10 g of tryptone, 10 g of NaCl, 15 g of agar powder in 1000 ml of dH2O, and adjust the pH to 7 in a 1000 ml reagent bottle.

[0032] 3. Purification of strains

[0033] Purify by the streak plate method. Dip a small amount of bacterial liquid with an inoculation loop and start streaking at the edge of one side of the plate. When streaking, the inoculation loop forms an angle of about 30 - 40 degrees with the surface of the plate, gently touch the plate, and streak at an appropriate speed and strength. The area of the first streak should be as small as possible. Then sterilize the inoculation loop by burning, and after cooling, start the second streak from the end of the first streak, making the lines partially overlap. Repeat this 3 - 4 times. Repeat 3 times for each gradient. After there are no contaminants, start preservation and identification.

[0034] 4. Identification of strains

[0035] DNA extraction: Extract the DNA of the strain using a bacterial genomic DNA extraction kit (brand: Tiangen; product number: DP302).

[0036] Using the obtained bacterial DNA as a template, amplify the 16S rDNA sequence with the universal primer pair 27F (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.1) / 1492R (5'-TACGGTTACCTTGTTACGACTT-3, SEQ ID NO.2) and perform electrophoresis detection.

[0037] The total volume of the PCR reaction system is 20 μL: 1 μL of DNA template, 10 μL of 2× EasyTaq ® PCR SuperMix, 1 μL each of the upstream and downstream primers, and ddH2O is added to make up to 7 μL.

[0038] Amplification program: pre-denaturation at 94 °C for 5 min; denaturation at 94 °C for 30 s; annealing at 54 °C for 30 s, extension at 72 °C for 1 min 30 s; final extension at 72 °C for 10 min; 35 cycles.

[0039] The PCR products were sent to Beijing Ruibo Xingke Biotechnology Co., Ltd. for 16S rDNA gene sequence sequencing. After successful sequencing, the sequences were assembled into one sequence, and txt and fasta format files were created for Blast homology search and comparison. Then, a phylogenetic tree was constructed using the Neighbor-Joining method in MEGA (10.2.4) software to determine the phylogenetic status of the strains.

[0040] Table 1 Taxonomic status of 8 strains

[0041] Finally, 8 excellent strains from 3 genera were isolated (Table 1). Among them, the similarity between strain No. 16S-YP-8 and strain Sinorhizobium fredii strain DB23-1 was the highest, reaching 99%; the similarity between strain No. 16S-GU-C6-12 and strain Sinorhizobium sp. XGL154 was the highest, reaching 99%; both were Rhizobium sinense ( Sinorhizobium ). The similarity between strain No. 16S-WP-A3-17 and 16S-YP-A3-7 and strain Burkholderia sp.YP-AN-3 was the highest, reaching 99%; the similarity between strain No. MCWP-A3-15 and strain Burkholderia sp.DCY113 was the highest, reaching 99%; both were Burkholderia ( Burkholderia ). The similarity between strain No. 16S-YP-2 and strain Paenibacillus illinoisensis strain LB170 was the highest, reaching 99%; the similarity between strain No. 16S-WP-B4-13 and strain Paenibacillus agarexedens strainCJ64 was the highest, reaching 99%; the similarity between strain No. 16S-WP9-2 and strain Paenibacillus polymyxa strain JK1 was the highest, reaching 99%; all were Paenibacillus ( Paenibacillus ).

[0042] Example 2. Growth promotion effect of plant growth-promoting rhizobacteria on aseptic potted seedlings in the laboratory

[0043] 1. Seed treatment

[0044] Select plump and uniform-sized alfalfa seeds. After disinfecting with 6% sodium hypochlorite for 5 min, rinse them 3 times with distilled water. Place them in a sterile petri dish and germinate in an incubator at a constant temperature of 28°C. After the germ breaks through the seed coat, select seeds with consistent germination and place them in small pots (7 cm in diameter and 10 cm in height) filled with 100 g of sterilized substrate (vermiculite and sand at a ratio of 1:1), one seed per pot. Place the small pots in an artificial climate chamber and maintain the water holding capacity of the substrate at 70%.

[0045] 2. Inoculation treatment

[0046] When the alfalfa seedlings grow the first true leaf, inoculate them with the 8 strains obtained in Example 1 respectively. The specific inoculation method is: irrigate the roots once every 2 days, 1 mL of bacterial solution each time (bacterial concentration is 10 8 CFU / mL). There are a total of 8 treatment groups. Starting from the first inoculation time, measure the plant height, root length, and dry weight per plant of the seedlings after 45 days.

[0047] 3. Control treatment

[0048] When the alfalfa seedlings grow the first true leaf, do not irrigate with the bacterial solution, but add an equal amount of sterile water for treatment as a control (CK).

[0049] 4. Growth promotion effect

[0050] Plant height is an intuitive manifestation of the growth vitality of alfalfa. A higher plant height usually means that the plant performs well in longitudinal growth, reflecting more active elongation and division activities of plant cells. At the same time, there is generally a positive correlation between the plant height of alfalfa and the hay yield. A higher plant height usually means more above-ground biomass accumulation, and a higher yield can be obtained when making hay. For alfalfa with a higher plant height, the total amount of its stems and leaves is relatively more. After harvesting, drying and other treatments, more hay products can be obtained. Therefore, conducting research on the plant height of alfalfa is of great significance for the alfalfa hay yield. As Figure 2 shown, the growth promotion abilities of different strains are different, and the plant heights of alfalfa under different treatments have all increased to varying degrees (P<0.01). The plant heights of alfalfa inoculated with 8 plant growth-promoting rhizobacteria are all significantly higher than that of CK (P<0.01), and the plant height has increased by 9.6% - 60.36% compared with CK. Among them, MCWP-A3-15 has the best growth promotion effect, and the plant height has increased by 60.36%. The order of the effects of the remaining strains on the plant height of alfalfa is: 16S-GU-C6-12>16S-YP-A3-7>16S-WP-B4-13>16S-YP-8>16S-WP9-2>16S-WP-A3-17>16S-YP-2.

[0051] Root length is a key indicator for alfalfa to adapt to soil conditions. The growth status of its root system directly affects the growth and yield of the above-ground part. A longer root length means a more developed root system, which can better absorb water and nutrients from the soil, thus providing an adequate material basis for the growth of the above-ground stems and leaves. Vigorously growing stems and leaves can effectively increase the alfalfa yield. Studying the root length of alfalfa helps to understand its nitrogen fixation ability and the improvement effect on soil fertility under different soil conditions. Longer root systems can penetrate the soil, improve soil aeration and water permeability, promote the growth and reproduction of soil microorganisms, and are beneficial to the ecological restoration of degraded soils. Therefore, conducting research on the root length of alfalfa plants has an important impact on alfalfa yield. As Figure 2 shown, the root length of alfalfa increased after inoculating different plant growth-promoting rhizobacteria (PGPR) under sterile conditions. The root length of alfalfa under the MCWP-A3-15 treatment was significantly longer than that of the CK (P<0.01), with a 67.71% increase. There was no significant difference in the root length of alfalfa under the treatment of the other strains and the control group (P<0.01).

[0052] The dry weight per plant of alfalfa directly reflects the total amount of organic matter accumulated during the growth process of the plant and is a key indicator for measuring its degree of nutrient accumulation. A higher dry weight per plant indicates that alfalfa has synthesized and stored a large amount of organic substances such as carbohydrates, proteins, and fats through photosynthesis. Therefore, it is very necessary to study the effect of inoculating different PGPR on alfalfa yield. As Figure 3 shown, compared with the dry weight per plant of alfalfa under the control condition, the dry weight per plant of alfalfa increased after inoculating different PGPR. Among them, the growth effect of the dry weight per plant of alfalfa under the inoculation of MCWP-A3-15 was the best, with an increase of 61%. The order of the effects of the other strains on the dry weight per plant of alfalfa was: 16S-WP-A3-17>16S-YP-2>16S-YP-8>16S-YP-A3-7>16S-GU-C6-12>16S-WP-B4-13>16S-WP9-2.

[0053] In summary, Burkholderia sp. MCWP-A3-15 can promote the growth of alfalfa, increase plant height, root length, and dry weight per plant.

[0054] Example 3. Growth-promoting effect of plant growth-promoting rhizobacteria in the field

[0055] 1. General situation of the test plot soil

[0056] The physical and chemical properties of the test plot soil are shown in Table 2.

[0057] Table 2 Physical and chemical properties of the test plot soil

[0058] 2. Field inoculation treatment

[0059] The experiment adopted a completely randomized block design, with 9 treatments set up, including 8 bacterial treatments and 1 control treatment; each treatment had 3 replicates, for a total of 27 plots, with a plot area of 20 m 2 (4m×5m), with a 1 m interval between plots, and a weed control cloth was laid. The row and plant spacing was 50 cm, and sowing was done in holes. For single sowing, 3 - 5 seeds were sown per hole, and after emergence, 1 plant was left per hole for single sowing, and 1 plant was left for each in mixed sowing. The irrigation condition was sprinkler irrigation. When the alfalfa seedlings grew their first true leaf, root irrigation inoculation was carried out, and the inoculation amount was 5 mL of bacterial solution (bacterial concentration was 10 8 CFU / mL); the control treatment was root irrigation with an equal amount of sterile water.

[0060] 3. Determination and results of agronomic trait indicators The following indicators were measured at the early flowering stage of alfalfa: Plant height: 20 alfalfa plants were randomly selected from each plot, and the vertical height was measured. The results are as Figure 5 shown.

[0061] Root length: The 20 alfalfa plants whose plant height had been measured were dug out of the soil, and the alfalfa plants were carefully dug out of the soil intact, trying to keep the integrity of the roots. The roots were gently rinsed with clean water to remove the attached soil. The washed roots were placed flat on a piece of white paper, and the roots were stretched as much as possible with forceps to avoid root bending and overlapping. Then, using a ruler, along the main root and lateral roots of the root, starting from the base of the root, the length of each section of the root was measured, and the lengths of each section were added up to obtain the root length of a single alfalfa plant. The results are as Figure 4 shown.

[0062] Dry weight per plant: 20 alfalfa plants were randomly selected from each plot and carefully dug out of the soil, trying to ensure the integrity of the plants, including the stems, leaves, flowers, fruits above the ground and the roots below the ground. The collected alfalfa plants were rinsed with clean water to remove the attached soil, impurities, etc. For the roots, they were gently washed to avoid damage. After washing, the plants were placed on absorbent paper and gently blotted to remove the excess water on the surface. The pretreated alfalfa plants were put into an oven and dried at an appropriate temperature and time. Generally, they were first blanched at a temperature of about 105℃ for about 30 minutes, with the aim of quickly stopping the physiological and biochemical reactions in the plants and preventing further decomposition or transformation of substances. Then the temperature was adjusted to 70 - 80℃ and drying was continued until the weight difference between two consecutive weighings did not exceed the specified range. The results are as Figure 5 shown.

[0063] By Figure 4It can be seen that under the inoculation treatment of MCWP-A3-15, the alfalfa plant height was significantly higher than that of the control, and there was no obvious increase in alfalfa plant height under the treatment of other strains. The order of the effects of different strains on alfalfa plant height was: MCWP-A3-15 > 16S-WP9-2 > 16S-GU-C6-12 > 16S-YP-A3-7 > 16S-WP-B4-13 > 16S-YP-8 > 16S-YP-2 > 16S-WP-A3-17. MCWP-A3-15 had a better effect on promoting the growth of root length than other strains.

[0064] As Figure 5 shown, inoculating different strains in the field had a certain growth-promoting effect on the dry weight per plant of alfalfa, and the growth-promoting effects of different strains were different. The growth-promoting effect of the dry weight per plant of alfalfa under the treatment of MCWP-A3-15 was the most obvious, and the dry weight per plant of alfalfa increased by about 33%. The dry weight per plant of alfalfa under the treatments of strains 16S-WP-B4-13, 16SYP-2, 16S-WP9-2, 16S-YP-8, 16S-WP-A3-17, etc. increased by 4%, 7%, 8%, 13%, 15%, etc. respectively.

[0065] 4. Determination of soil physical and chemical property indexes Adequate macronutrients such as nitrogen, phosphorus, and potassium, as well as micronutrients such as iron and zinc in the soil are crucial for plant growth and development. Nitrogen is one of the key nutrient elements affecting alfalfa plant height, and it is an important component of plant proteins and nucleic acids. If the nitrogen supply in the soil is sufficient, the plant grows vigorously and the plant height increases significantly; on the contrary, the lack of nitrogen will lead to slow growth of alfalfa and a decrease in plant height. Phosphorus is involved in processes such as plant energy metabolism and cell division. Sufficient supply of phosphate fertilizer can promote the growth of plant roots and the increase in plant height of the above-ground part.

[0066] Determination of soil pH value: Weigh a certain amount of air-dried soil sample and put it into a triangular flask. Add carbon dioxide-free distilled water according to the soil-water ratio of 1:2.5 (mass ratio), shake for a certain time and then let it stand. Insert the glass electrode and the calomel electrode into the supernatant, and use a pH meter to measure the pH value of the solution. The results are as Figure 6 shown.

[0067] Determination of soil organic matter content: Accurately weigh a certain amount of air-dried soil sample, add an excessive amount of potassium dichromate-sulfuric acid solution, oxidize the organic matter in the soil under the condition of oil bath, titrate the remaining potassium dichromate with a standard solution of ferrous sulfate, and calculate the soil organic matter content according to the amount of ferrous sulfate consumed. The results are as Figure 7 shown.

[0068] Determination of total nitrogen content in soil: The soil sample is heated and digested together with concentrated sulfuric acid and a catalyst to convert organic nitrogen into ammonium sulfate. Then, alkali is added for distillation to release ammonia, which is absorbed by boric acid solution. Subsequently, the ammonia absorbed by the boric acid solution is titrated with a standard acid solution, and the total nitrogen content in the soil is calculated based on the amount of acid used. The results are as Figure 8 shown.

[0069] Determination of available phosphorus content in soil: Weigh 2.50 g of air-dried soil sample passing through a 2-mm sieve pore into a 250-ml plastic bottle. Add 50.0 ml of 0.5 mol / L sodium bicarbonate solution (pH 8.5), shake for 30 min at 20 - 25 °C, and then filter with a phosphorus-free filter paper. Pipette 10.0 ml of the filtrate into a 50-ml volumetric flask, add 5 ml of ammonium molybdate-sulfuric acid solution, then add 5 ml of ascorbic acid solution, make up the volume with water, and shake well. After standing for 30 min, colorimetric determination is carried out at a wavelength of 700 nm. The results are as Figure 9 shown.

[0070] It can be Figure 6 seen that the pH values of the soils in each treatment are all 8.5 - 8.7, and there are no significant differences among the treatments (P > 0.01). The contents of organic matter, total nitrogen, and available phosphorus are positively correlated with soil fertility. From Figure 7 it can be seen that MCWP-A3-15 has little effect on the organic matter content. From Figure 8 it can be seen that the total nitrogen content in the MCWP-A3-15 treatment is significantly increased compared with CK, and there are no significant differences between the 16S-WP-A3-17 and 16S-GU-C6-12 treatments and CK. From Figure 9 it can be seen that the available phosphorus in the treatments with different strains all increases to varying degrees (P < 0.01). Among them, the increase in the MCWP-A3-15 treatment is significant, which is 1.3 times that of CK. In summary, Burkholderia sp. MCWP-A3-15 can promote the growth of alfalfa, increase plant height, root length, and dry weight per plant; it can also improve the physical and chemical properties of the soil, increase the total nitrogen content and available phosphorus content in the soil, and enhance soil fertility.

Claims

1. A plant growth-promoting rhizobacterium that can effectively increase the growth of alfalfa, characterized in that, The plant growth-promoting rhizobacteria is Burkholderia sp. MCWP-A3-15; the preservation number of Burkholderia sp. MCWP-A3-15 is CGMCC No. 31562, and it is preserved in the China General Microbiological Culture Collection Center.

3. Use of Burkholderia sp. MCWP-A3-15 according to claim 2 in promoting the growth of alfalfa, characterized in that, 2. Use of the Burkholderia sp. MCWP-A3-15 according to claim 1 in promoting the growth of alfalfa.

4. Use of Burkholderia sp. MCWP-A3-15 according to claim 1 in improving physical and chemical properties of soil, characterized in that, Burkholderia sp. MCWP-A3-15 can increase the plant height, root length and dry weight per plant of alfalfa. The physical and chemical properties include total nitrogen content and available phosphorus content.

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