Nissonia nielsonii with plant rhizosphere growth promoting effect and application of nissonia nielsonii

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to Nelsenia nielsenensis with a plant rhizosphere growth promoting effect and application of the Nelsenia nielsenensis. The bacterial strain is Niallia nealsonii BN5, and the preservation number of the bacterial strain is CGMCC (China General Microbiological Culture Collection Center) No.31380. The Nissenia nielsonii BN5 provided by the invention has a relatively large growth temperature range, is easy to adapt to various soil environments, and has the characteristics of dissolving phosphorus, producing IAA (Indoleacetic Acid) and the like; the invention provides a novel method for promoting plant growth in crop production, which is helpful for improving crop yield and quality and promoting sustainable agricultural development at the same time. The technology is not only limited to cucumbers, but also can be applied to planting of other crops, and important technical progress and economic benefits are brought to modern agricultural production. The method has a wide application prospect and is suitable for sustainable development and production optimization of modern greenhouse agriculture.

Description

Technical Field

[0001] The present invention belongs to the field of microbial technology, and specifically relates to a strain of Nelsonia bacteria ( Niallia nealsonii BN5) and its applications. Background Art

[0002] Nelsonia Niallia nealsonii ) is a member of the genus Bacillus and is commonly found in the natural environment, including soil, water, and inside plants.

[0003] In agricultural production, especially in the field of greenhouse crop cultivation, improving crop yield and quality has always been an important research direction. Traditional agriculture relies on chemical fertilizers to promote crop growth, but long-term use has brought many problems such as soil compaction and environmental pollution. Therefore, it is crucial to seek green, environmentally friendly and effective growth promotion methods. Microbial fertilizers, as a new type of fertilizer, have received widespread attention. PGPR plays an important role in facility agriculture and can directly or indirectly promote plant growth through a variety of mechanisms. They can produce plant growth hormones, such as auxins, gibberellins and cytokinins, which stimulate plant cell division and elongation, promote root growth and plant development 。

[0004] Due to the wide variety of biosource materials and the fact that the effects of growth-promoting bacteria are easily affected by environmental conditions, the current growth-promoting effect of growth-promoting bacteria in crop cultivation is not ideal. Summary of the invention

[0005] The purpose of the present invention is to provide a strain of Nelsonia bacteria ( Niallia nealsonii BN5).

[0006] Another object of the present invention is to provide the use of the above-mentioned Nelsonia in crop growth promotion.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: The present invention provides a strain of Nelsonia bacteria having a plant rhizosphere growth-promoting effect, wherein the strain is Niallia nealsonii BN5, with the deposit number CGMCC No.31380, is deposited in the General Microbiology Center of China Culture Collection Administration, and the deposit date is July 22, 2024.

[0008] The present invention also provides the use of the Nelsonia bacteria in promoting the growth of crops.

[0009] Another object of the present invention is to provide a crop growth promoter prepared using the above-mentioned Nelsonia bacteria.

[0010] Preferably, the crop growth promoter contains a culture, a culture concentrate, a culture suspension or a volatile organic compound (VOC) of Nelsonia spp.

[0011] The Nelsonia bacteria provided by the present invention ( Niallia nealsonii BN5), which has the ability to solubilize phosphate and produce IAA.

[0012] The fresh weight of Arabidopsis roots increased by 135.29% and 82.35% in the proximal and distal treatments, respectively, and the length of the main root was significantly increased, and the number of lateral roots increased significantly, indicating that BN5 has a strong promoting effect on the roots. A specific analysis of its underground part found that after exogenous addition of BN5 for proximal and distal treatments, the length of the main root increased by 12.22% and 27.52%, the number of lateral roots increased by 683.33% and 600.00%, the root surface area increased by 58.18% and 62.26%, and the density increased by 533.86% and 196.75%.

[0013] After exogenous addition of Nelsonia BN5, the growth of cucumber seedlings was significantly higher than that of the control group. Its above-ground fresh weight increased by 34.10%, its underground fresh weight increased by 288%, and the number of root tips increased significantly, indicating a stronger effect on the root. A specific analysis of its underground part found that after exogenous addition, its taproot length increased by 40.95%, the number of root tips increased by 78.49%, the root area increased by 30.87%, and the total root surface area increased by 12.37%.

[0014] After the indirect regulation of Nelsonia BN5 on cucumber, the growth of crop seedlings was significantly higher than that of the control group, with its above-ground fresh weight increasing by 169.23% and underground fresh weight increasing by 876.19%, indicating a stronger promoting effect on the roots. A specific analysis of its underground part found that after exogenous addition, its taproot length increased by 13.31%, the number of root tips increased by 50.22%, and the root area increased by 4.39%. The total root surface area, total root volume and average diameter were relatively less affected.

[0015] After applying Nelsonia BN5, wheat growth was significantly higher than the control group, with its aboveground dry weight increasing by 23.49% and root dry weight increasing by 11.48%, indicating a stronger effect on the aboveground part of wheat. A specific analysis found that after adding BN5, the taproot length increased by 21.30%, the stem diameter increased by 27.45%, and the seedling index of wheat treated with Nelsonia BN5 was higher than that of the control group.

[0016] The crop growth promoting agent provided by the present invention comprises the following steps: the culture containing Nelsonia bacteria is prepared by inoculating Nelsonia bacteria BN5 into a NB liquid culture medium for shaking culture; the culture containing Nelsonia bacteria is concentrated to obtain a BN5 culture concentrate; the culture containing Nelsonia bacteria is centrifuged, the supernatant is removed, and the bacteria are added to sterile water for re-suspending to obtain a BN5 bacterial suspension; and Nelsonia bacteria BN5 is inoculated into a NB solid culture medium, statically cultured, and volatiles thereof are collected to obtain volatile matter VOCs thereof.

[0017] Furthermore, the culture containing Nelsonia bacteria, BN5 culture concentrate, and BN5 bacterial suspension are prepared by the following method: (1) Inoculate a single colony of purified Nelsonia BN5 into 5 mL NB liquid culture medium and culture overnight until OD ≈ 1.0, then inoculate into new NB liquid culture medium at 5 wt% and culture at 30 °C, 180 rpm, with shaking for 20-24 h to obtain a culture containing Nelsonia; (2) Centrifuge the culture containing Nelsonia, remove the supernatant and keep only the bacteria, then add sterile water to suspend the bacteria to obtain BN5 bacterial suspension.

[0018] Preferably, the OD of the culture containing Nelsonia 600 The value is 1 to 1.5.

[0019] Preferably, the centrifugation is carried out at 5000-7000 rpm for 3-5 min.

[0020] Beneficial effects of the present invention: (1) In the present invention Niallia nealsonii BN5 was isolated from the rhizosphere soil of the greenhouse, has a wide growth temperature range, is easily adapted to various soil environments, and has the characteristics of solubilizing phosphate and producing IAA; (2) The present invention provides a new method for promoting plant growth in crop production, which helps to improve crop yield and quality and promote sustainable agricultural development. This technology is not limited to cucumbers, but can also be applied to the cultivation of other crops, bringing important technological progress and economic benefits to modern agricultural production; it has broad application prospects and is suitable for the sustainable development and production optimization of modern greenhouse agriculture.

[0021] Collection Information Preservation time: July 22, 2024; Depository: General Microbiology Center, China Microbiological Culture Collection Administration; Deposit number: CGMCC No.31380; Address of the depository: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing; Postal code: 100101; Category naming: Niallia nealsonii . BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The electrophoresis detection result of the 16S rRNA PCR amplification product of Nelsonia BN5 provided by the present invention; Figure 2 The BN5 phylogenetic tree based on 16S rRNA sequence homology provided by the present invention; Figure 3 The different temperature growth curves of Nelsonia sp. BN5 provided by the present invention are 20°C, 25°C, 30°C, 35°C, and 40°C from top to bottom; Figure 4 The phosphate solubilization assay of Nelsonella BN5 provided by the present invention, A: transparent zone size B: phosphate solubilization standard curve; Figure 5 The IAA production capacity determination of Nelsonia sp. BN5 provided by the present invention, A: Salkowski colorimetric result B: IAA production standard curve; Figure 6 This is a diagram showing the growth of Arabidopsis seedlings with exogenously added Nelsonia bacteria BN5 provided by the present invention; from left to right, they are CK group, BN5 (proximal end), and BN5 (distal end); Figure 7 This is a diagram showing the growth of cucumber seedlings with exogenous addition of Nelsonia bacteria BN5 provided by the present invention; the left side is the CK group, and the right side is BN5; Figure 8 This is a diagram of the indirect regulation of cucumber growth by exogenous addition of Nelsonia bacteria BN5 provided by the present invention; the left side is the CK group, and the right side is BN5; Fig. 9 A diagram showing the effect of applying Nelsonia bacteria BN5 on wheat growth in the field provided by the present invention; the left side is the CK group, and the right side is BN5. DETAILED DESCRIPTION

[0023] The present invention is further explained below with reference to the examples, but the examples do not limit the present invention in any form.

[0024] The present invention screened out a plant from the rhizosphere soil of the greenhouse. Niallia nealsonii , explore its growth-promoting function, and explore its effect on the growth of greenhouse crops. N. nealsonii Provide strain resources for related research.

[0025] The NB (Nutrient Broth) medium used in the present invention contains 10.0 g of peptone, 3.0 g of beef extract powder and 5.0 g of sodium chloride, which are placed in 1 L of water and have a pH of 7.2±0.2.

[0026] Example 1 Niallia nealsonii Isolation and identification of BN5 1. Niallia nealsonii Isolation of BN5 10 g of fresh soil sample from the greenhouse rhizosphere was collected from the greenhouse vegetable planting area and placed in a triangular flask containing 90 mL of sterile water and a small amount of glass beads. The flask was placed in a 30 °C constant temperature shaker and cultured at 180 rpm for 30 min to evenly disperse the soil sample in the diluent (sterile water) to make 10 -1 Dilution. Pipette 1 mL 10 -1 The dilution was placed in a glass test tube containing 9 mL of sterile water and shaken to make 10 -2 Diluent. And so on, continue diluting until the dilution reaches 10- 7 . Select 10- 5 、10- 6 、10- 7 100 μL of the three dilution gradients of soil dilution were respectively applied to NB solid medium (NB liquid medium with 12 g / L agar powder) plates and cultured at 30 °C for 24 h. After the microbial colonies grew on the plates, strains with different colony morphology were selected and transferred to NB solid medium by streaking and cultured at 30 °C for 24 h. In this way, the streaking purification culture was carried out for more than 3 times, and the purity was examined under a microscope until a pure culture was obtained. The bacterial solution was preserved with 30% glycerol and stored in a -20 °C refrigerator for later use. A total of 36 bacterial strains were isolated. Whether a transparent circle appeared around the colony on PVK (Pikovskaya) inorganic phosphorus medium (purchased from Beijing Coolbo Technology Co., Ltd.) and whether indoleacetic acid reacted with Salkowski reagent to produce pink, a strain with both phosphate solubilization and IAA production was finally screened.

[0027] 2. Niallia nealsonii Identification of BN5 The purified Nelsonia BN5 single colony was inoculated into 5 mL NB liquid medium and cultured overnight to OD≈1.0, and then inoculated into new NB liquid medium at a rate of 5wt%, and cultured at 30°C, 180 rpm, and shaking for 24 h. The cultured fermentation broth was used to extract DNA using the Ezup column bacterial genomic DNA extraction kit. After DNA extraction, 16SrDNA was amplified by PCR.

[0028] The 16S rRNA amplification primers 27F (SEQ ID NO: 1) and 1492R (SEQ ID NO: 2) were used as upstream and downstream primers. Niallia nealsonii The total bacterial DNA was used as a template for PCR amplification, and the amplified products were detected by agarose gel electrophoresis.

[0029] like Figure 1 As shown in the figure, the expected specific band appeared at 1000-2000bp, indicating that the 16S rRNA amplification was successful. The 16S rRNA PCR product detected by electrophoresis was sent to Shandong Huabo Gene Engineering Co., Ltd. for sequencing, and the sequencing results were compared in GenBank. The sequence is as follows. The results showed that the BN5 strain was inferred to be Nelsonia by comparison with NCBI and named Niallia nealsonii BN5, whose phylogenetic analysis is shown in Figure 2 shown.

[0030] SEQ ID NO:1 AGAGTTTGATCMTGGCTCAG SEQ ID NO:2 TACGGYTACCTTGTTACGACTT SEQ ID NO:3 BN5 16S rRNA sequence

[0031] The isolated and purified strain is a Nelsonia strain ( Niallia nealsonii BN5), which has been deposited in the General Microbiology Center of China Microorganism Culture Collection Committee, the deposit location is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, the deposit number is CGMCC NO.31380, and the deposit date is July 22, 2024.

[0032] Example 2 Determination of biological properties of Nelsonella BN5 1. Growth curve determination The purified Nelsonia BN5 single colony was inoculated into 5 mL NB liquid medium and cultured overnight until OD ≈ 1.0. It was inoculated into new NB liquid medium at 5wt% and cultured at 30°C and 180 rpm for 24 h to make the BN5 strain active. The activated bacterial solution was inoculated into 50 mL NB liquid medium at 5wt% inoculation and cultured at 180 rpm at 20, 25, 30, 35 and 40°C. The bacterial solution OD was measured every 2 h. 600 The OD value was adjusted until it became stable. Three groups were made in parallel, and the growth curve was drawn with blank culture medium as the control. Figure 3 As shown, the BN5 strain reached the logarithmic phase most quickly at 40°C. After reaching the stationary phase at 20°C, 25°C, 30°C, and 40°C, there was no significant difference in the bacterial growth. However, under the 35°C culture condition, it showed a trend of secondary growth after reaching the stationary phase for a period of time.

[0033] 2. Determination of the ability to dissolve organic phosphorus A single colony of purified Nelsonia BN5 was inoculated into 5 mL NB liquid medium and cultured overnight to OD≈1.0. Then, 5 wt% of the colony was inoculated into new NB liquid medium and cultured at 30 °C and 180 rpm for 24 h to keep the BN5 strain active. The culture was continued until OD 600 =0.8. 3 μL of the activated bacterial solution was inoculated into the PVK inorganic phosphorus medium and cultured in a 30°C constant temperature incubator for 7 days to observe and record whether the strain produced a phosphate solubilization circle. The size of the phosphate solubilization circle can be used as a sign of the strength of phosphate solubilization. The larger the phosphate solubilization circle, the stronger the phosphate solubilization ability of the strain. Repeat three times. The results are as follows: Figure 4 The diameter of the phosphate solubilization zone (D) and the diameter of the colony (d) were recorded, and the D / d value was 1.22. At the same time, the activated bacterial solution was inoculated with 2wt% inoculation into 50 mL of inorganic phosphorus liquid culture medium and cultured at 30°C and 180 rpm for 7 days. The molybdenum antimony colorimetric method was used to determine the phosphate solubilization amount. The curve equation was y=0.5216x+0.0003, R 2=0.9986, and its solubilized phosphorus content was 3.221±0.013 μg / mL.

[0034] 3. Determination of IAA production capacity Preparation of Salkowski colorimetric solution: Mix 50 mL of 35% HClO4 and 1 mL of 0.5 mol / L FeCl3, place in a brown bottle, and prepare before use.

[0035] A single colony of purified Nelsonia nematodes BN5 was inoculated into 5 mL NB liquid medium and cultured overnight until OD ≈ 1.0. Then, 5 wt% of the colony was inoculated into new NB liquid medium and cultured at 30 °C, 180 rpm for 24 h. The colony was centrifuged at 8000 rpm, rinsed with sterile water, and the OD was adjusted. 600 =0.8, 200 μL of bacterial solution was inoculated into 4 mL (containing 1% 200 mg / L L-tryptophan) NB liquid medium, and the medium without bacterial solution was used as blank control. Each treatment was repeated 3 times, and cultured at 28°C and 180 rpm for 4 days. After the culture, the bacterial solution was centrifuged at 8000 rpm for 10 min, 1 mL of the supernatant was taken, and an equal volume of Salkowski colorimetric reagent was added. It was kept away from light for 30 min and its color change was observed. If the color turns red, it is considered to have the ability to produce IAA. The darker the color, the stronger the IAA synthesis ability. The results are as follows Figure 5 At the same time, the absorbance was measured at a wavelength of 530 nm using a UV-visible spectrophotometer, and the IAA content was calculated by comparing it with the standard curve. The standard curve was drawn by gradient dilution of the IAA analysis standard. The curve equation is y=0.0326x+0.0068, R 2 =0.9994, and the IAA production per unit of BN5 was measured to be 8.69±0.11 μg / mL.

[0036] Example 3 Determination of the growth-promoting ability of Nelsonella BN5 Prepare 0.2 M MS solid medium (MS (MS Medium) medium contains 1.9 g potassium nitrate, 1.65 g ammonium nitrate, 0.17 g potassium dihydrogen phosphate, 0.37 g magnesium sulfate, 0.44 g calcium chloride, 12 g agar powder, etc., in 1L water, pH 5.7±0.1.), add about 25 mL MS solid medium to each square culture dish. Select Arabidopsis wild type Columbia-0 (Col-0): 2.5% sodium hypochlorite disinfection for 3 minutes during continuous shaking, rinse with sterile water 3 times, then disinfect with 70% alcohol for 3 minutes, rinse the seeds with sterile water, rinse for 3 minutes each time, and wash 3 times. Use a sterile pipette tip to point the disinfected seeds at 1 / 3 of the solid medium, place 8 seeds on each plate, dry them, seal the plates and put them in a 4℃ refrigerator for vernalization for two days.

[0037] Inoculate a single colony of purified Nelsonia BN5 into 5 mL NB liquid medium and culture overnight until OD≈1.0. Inoculate 5 wt% of the colony into a new 10 mL NB liquid medium and culture overnight. The next day, centrifuge the cells at 4°C and 7000 rpm, remove the supernatant, and keep only the cells. Add an appropriate amount of sterile water to suspend the cells until OD 600 The value is 1, and 40 μL is pipetted onto the 1 / 2 of the plate. The culture dish is placed in a growth chamber at 25 °C and cultured vertically with a light photoperiod of 16 h and a dark photoperiod of 8 h. Observe, measure and take photos for 10 days.

[0038] The results are as follows Figure 6 As shown in the figure, the fresh weight of roots in the proximal and distal treatments increased by 135.29% and 82.35%, respectively, and the main root length was significantly improved, and the number of lateral roots increased significantly, indicating that Nelsonia BN5 had a strong promoting effect on roots. A specific analysis of its underground part found that after exogenous addition of Nelsonia BN5 for proximal and distal treatments, the main root length increased by 12.22% and 27.52%, the number of lateral roots increased by 683.33% and 600.00%, the root surface area increased by 58.18% and 62.26%, and the density increased by 533.86% and 196.75%. The growth indicators are shown in Table 1.

[0039] Table 1

[0040] Example 4 Verification of the Growth-Promoting Ability of Nelsonella BN5 on Cucumber 1. Pretreatment of cucumber seeds with Nelsonia niger BN5 strain Pretreatment of cucumber seeds: Place cucumber seeds in a 55 ℃ water bath, heat shock for 5 min, first disinfect with 70% alcohol for 1 min, then disinfect with 4% sodium hypochlorite solution for 7 min, and finally rinse with sterile water 7-8 times. Inoculate greenhouse crop seeds into MS solid culture medium and culture in the dark at 25 ℃ for 2 days.

[0041] Pretreatment of Nelsonia BN5: Inoculate a single colony of purified Nelsonia BN5 into 5 mL NB liquid medium overnight and culture until OD≈1.0, then inoculate into new NB liquid medium at 5wt%, and culture at 30°C, 180rpm for 24 h to make Nelsonia BN5 active. Take 1 mL of bacterial solution in a 1.5 mL centrifuge tube, centrifuge at 5000 rpm for 3 min, remove the supernatant, and use 1 mL ddH2O to fully disperse and mix the precipitate to make the BN5 bacterial suspension OD600≈1.5.

[0042] 2. Effect of exogenous addition of Nelsonia niger BN5 on cucumber seedlings Cucumber seedlings with a bud length of about 1 cm after the above pretreatment were selected and transplanted into blank MS medium. Five seedlings were transplanted into each plate, and 120 μL of BN5 bacterial suspension was dripped onto the roots of the seedlings. The seedlings were placed in a light incubator for 14 days (16 h at 26 °C under a light intensity of 15000 Lux and 8 h at 18 °C in the dark). The growth index of the seedlings was measured. ddH2O was dripped onto the roots of the cucumber seedlings as a control, and three parallel experiments were set up for each group of experiments.

[0043] After exogenous addition of BN5 bacterial suspension, the growth of cucumber seedlings was significantly higher than that of the control group. Figure 7 As shown. However, the difference in germination rate was small, indicating that Nelsonia BN5 had little effect on cucumber seed germination. Its above-ground fresh weight increased by 34.10%, underground fresh weight increased by 288%, and the number of root tips increased significantly, indicating a stronger effect on root promotion. A specific analysis of its underground part found that after exogenous addition, its taproot length increased by 40.95%, the number of root tips increased by 78.49%, the root area increased by 30.87%, and the total root surface area increased by 12.37%. The growth indicators are shown in Table 2.

[0044] Table 2

[0045] 3. Indirect regulation of BN5 on the promotion of cucumber seedlings Take 9 μL of the BN5 bacterial suspension obtained in the above steps and divide it into three drops, drop it on one side of the beef extract peptone medium in the two-divided culture dish, and culture it at 30 ℃ for three days. Select cucumber seedlings with a bud length of about 1 cm after pretreatment and transplant them to the other side of the two-divided plate containing MS medium. Each plate is transplanted with 2 seedlings, sealed with sealing film, and placed in a light incubator for 14 days (cultured at 26 ℃ for 16 h under light intensity of 15000 Lux, and cultured at 18 ℃ for 8 h under dark conditions), and then measure the growth indicators of the seedlings. Add ddH2O to one side of the beef extract peptone medium as a control, and set up three parallels for each group of experiments.

[0046] The results are as follows Figure 8 As shown in the figure, after the indirect regulation of Nelsonia BN5 on cucumber, the growth of cucumber seedlings was significantly higher than that of the control group, with its above-ground fresh weight increased by 169.23% and underground fresh weight increased by 876.19%, indicating a stronger promotion effect on the roots. A specific analysis of its underground part found that after exogenous addition, its taproot length increased by 13.31%, the number of root tips increased by 50.22%, and the root area increased by 4.39%. The total root surface area, total root volume and average diameter were relatively less affected. The growth indicators are shown in Table 3.

[0047] Table 3

[0048] Example 5 Verification of the ability of Nelsonia nielsenii BN5 to promote wheat growth in the field Select wheat seeds suitable for local sowing and sow them in the divided field plots in Tai'an City, Shandong Province before October 9, 2024. Nelsonia BN5 was cultured and fermented in the laboratory, and the effective viable count reached 1.03×10 9 CFU / g or more. Sprinkle the BN5 microbial agent evenly on the crushed peat soil at a ratio of 20%, and then use a mixer to mix it thoroughly. Sprinkle the obtained microbial agent evenly in the field plot, and turn the soil and sow according to the local wheat planting method. Sampling was carried out on November 22, 2024, with 3 points in each plot and 2-3 trees at each point. Take pictures of the whole wheat plant, measure the stem thickness, root length, number of leaves, and plant height, and dry the aboveground part and the root system separately to determine the dry weight. According to the formula, the seedling index = (stem thickness / plant height + root dry weight / aboveground dry weight) × whole plant dry weight, calculate its seedling index, and use the peat soil alone as a control.

[0049] The results are as follows Fig. 9 As shown in the figure, after applying Nelsonia BN5, the growth of wheat was significantly higher than that of the control group, with its aboveground dry weight increasing by 23.49% and its root dry weight increasing by 11.48%, indicating that the promotion effect on the aboveground part of wheat was stronger. A specific analysis showed that after adding Nelsonia BN5, the taproot length increased by 21.30%, the stem diameter increased by 27.45%, and the seedling index of wheat with Nelsonia BN5 was higher than that of the control group. The specific growth indicators are shown in Table 4.

[0050] Table 4

Claims

1. A strain of Nelsonia sp. BN5 having a plant rhizosphere growth promoting effect, characterized in that: The strain is Niallia nealsonii BN5, with the deposit number CGMCC No.31380, is deposited in the General Microbiology Center of China Culture Collection Administration, and the deposit date is July 22, 2024.

2. Use of the Nelsonia bacteria BN5 as claimed in claim 1 in promoting crop growth.

3. A crop growth promoter prepared using the Nelsonia sp. BN5 as claimed in claim 1.

4. The crop growth promoting agent according to claim 3, characterized in that The crop growth promoter contains Nelsonia culture, BN5 culture concentrate, BN5 bacterial suspension or its volatile matter VOC.

5. The crop growth promoting agent according to claim 4, characterized in that The culture containing Nelsonia bacteria is prepared by inoculating Nelsonia bacteria BN5 into NB liquid culture medium for shaking culture; concentrating the culture containing Nelsonia bacteria to obtain BN5 culture concentrate; centrifuging the culture containing Nelsonia bacteria, removing the supernatant, and resuspending the bacteria in sterile water to obtain BN5 bacterial suspension; inoculating Nelsonia bacteria BN5 into NB solid culture medium, statically culturing, and collecting its volatiles to obtain its volatile VOCs.

6. The crop growth promoting agent according to claim 5, characterized in that The inoculation amount of the Nelsonia sp. BN5 in the NB liquid culture medium or the NB solid culture medium is 5 wt %.

7. The crop growth promoting agent according to claim 5, characterized in that The conditions for shaking culture are: shaking culture at 180 rpm for 20-24 h; the conditions for static culture are: static culture at 30°C for 3-5 d.

8. The crop growth promoting agent according to claim 5, characterized in that The OD of the culture containing Nelsonia 600 The value is 1 to 1.

5.

9. The crop growth promoting agent according to claim 5, characterized in that: The centrifugation is carried out at 5000-7000 rpm for 3-5 min.

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