GROWTH-PROMOTING BACTERIAL AGENT CAPABLE OF IMPROVING CONTENT OF SOYBEAN OIL, PREPARATION METHOD AND USE THEREOF

Abstract

A growth-promoting bacterial agent capable of improving content of soybean oil, preparation method, and use thereof are provided. The growth-promoting bacterial agent is fermented by a DW1 strain, the classification name of the DW1 strain is Bacillus sp., the DW1 strain is deposited in the China Center for Type Culture Collection on Jul. 16, 2021, and the deposit number is CCTCC NO: M 2021889. The growth-promoting bacterial agent of the present disclosure has the ability to dissolve insoluble phosphorus and insoluble potassium and can increase content of readily available phosphorus and readily available potassium in the soil, which has an obvious promoting effect on the growth of soybean and improves soybean yield. The growth-promoting bacterial agent of the present disclosure promotes bacteria and can significantly improve the content of soybean oil. At the same time, it has an affinity of soybean agglutinin and can agglutinate with the soybean agglutinin.

Claims

1. A growth-promoting bacterial agent for soybeans, wherein the growth-promoting bacterial agent is fermented by a DW1 strain, the classification name of the DW1 strain is Bacillus sp., the DW1 strain is deposited in the China Center for Type Culture Collection on Jul. 16, 2021, and the deposit number is CCTCC NO: M 2021889.

2. The growth-promoting bacterial agent for soybeans according to claim 1, wherein the growth-promoting bacterial agent is a liquid bacterial agent.

3. The growth-promoting bacterial agent for soybeans according to claim 2, wherein the application amount of the liquid bacterial agent per hectare of soybean fields is 10-50 L, and a count of living bacteria in the liquid bacterial agent is within the range of 1×10.sup.8−9×10.sup.8 CFU.Math.mL.sup.−1.

4. A preparation method of the growth-promoting bacterial agent for soybeans according to claim 2, wherein the preparation method of the liquid bacterial agent comprises: S1. activating the DW1strain: inoculating the DW1 strain into an LB slope medium, and culturing the DW1 strain at 25-30° C. for 18-30 h; and S2. culturing the DW1 strain in a liquid medium: washing the DW1 strain on the LB slop medium with physiological saline, inoculating the DW1 strain into 80-120 mL of the LB liquid medium with a volume ratio of 2-5%, and placing the strain in a shaker at 25-30° C. and 120-180 r.Math.min.sup.−1 for shaking cultivation for 24-28 h to prepare the liquid bacterial agent.

5. A use of growth-promoting bacterial agent for soybeans according to claim 1, wherein the growth-promoting bacterial agent is used for at least one of seed soaking, coating, or root watering of soybeans.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows the influence of the DW1 bacteria agent provided by the present disclosure on soybean yield in field tests.

[0024] FIG. 2 shows the influence of the DW1 bacteria agent provided by the present disclosure on the oil content and protein content of soybean in field tests.

DETAILED DESCRIPTION

[0025] The following embodiments are further described by the present disclosure.

Embodiment 1

[0026] Strain Screening

[0027] Strong soybean plants were selected as samples, the roots of the soybean plants with soil were dug out, larger soil blocks and other useless residues were removed, 1 g of rhizosphere soil of each sample were took respectively to sterile physiological saline containing nystatin, and placed in a shaker for oscillating at 160 r.Math.min.sup.−1 for 0.5 h to obtain rhizosphere soil bacterial suspension. 1 mL of the above-mentioned bacterial suspension was took to 9 mL of sterile physiological saline containing nystatin, and gradient diluted to 10.sup.−7 concentration. The above-mentioned bacterial suspension was coated on a phosphate-dissolving and potassium-dissolving solid medium containing nystatin, repeated 3 times at each concentration, and cultured at the constant temperature of 28° C. for more than 3 days until a transparent ring appears.

[0028] The formula of the above phosphate-dissolving solid medium is as follows: glucose 10 g, K.sub.2HPO.sub.4 2.0 g, ammonium sulfate 0.5 g, NaCl 0.3 g, KCl 0.3 g, MgSO.sub.4.7H.sub.2O 0.3 g, FeSO.sub.4.7H.sub.2O 0.03 g, MnSO.sub.4.4H.sub.2O 0.03 g, Ca.sub.3(PO.sub.4).sub.2 10 g, agar 15 g, distilled water 1000 mL, pH 7.2.

[0029] The formula of the potassium-dissolving solid medium is as follows: Na.sub.2HPO.sub.4 2.0 g, MgSO.sub.4.7H.sub.2O 0.5 g, FeCl.sub.3 0.005 g, CaCO.sub.3 0.1 g, potassium feldspar 1.0 g, sucrose 5.0 g, agar 15 g, and distilled water 1000 mL, pH 7.0-7.5.

[0030] The diameter H of the transparent ring and the diameter C of a colony were observed and measured and the ratio of the two (H/C) was calculated. The strain with the larger H/C value has stronger phosphorus or potassium dissolving capacity.

[0031] The colonies with transparent rings were picked to the LB medium containing 50 mg.Math.L.sup.−1 nystatin, then streaked and purified a plurality of times to obtain a pure growth-promoting strain. The LB medium formula is peptone 10 g, yeast powder 5 g, NaCl 10 g, agar 15 g, and distilled water 1000 mL.

[0032] The growth-promoting strains obtained by screening were inoculated in LB liquid medium, shaked cultivation at constant temperature for 1 day to logarithmic phase, packaged the medium in a centrifuge tube, centrifuged at 3000 r.Math.min.sup.−1 for 10 min, and collected bacteria. The bacteria were putted into sterile water, the bacteria were blowed and sucked for a plurality of times by using a pipettor to disperse and suspend the bacteria, centrifuged and washed the bacteria, and repeated the steps 3 times to obtain the bacterial suspension. If the liquid is turbid by observation, a small amount of sterile water was added for dilution. 25 μL of the bacterial suspension were dripped to the center of the glass slide, mixed with soybean agglutinin of equal volume, stood at room temperature for 0.5 h, dried, and the reaction was observed under a microscope after dyeing.

[0033] The strains with agglutination reaction were picked to obtain soybean affinity growth-promoting strains. The DW1 applied for the present disclosure is the growth-promoting strain with soybean affinity obtained by the screening method.

Embodiment 2

[0034] Determination of Growth-Promoting Ability of the DW1 Strain

[0035] A double screening method of a selective medium and soybean agglutinin were adopted to screen growth-promoting bacteria with specific affinity with soybeans from the soybean rhizosphere, and the phosphorus-dissolving, potassium-dissolving, and IAA-producing abilities of the strains were determined. Bacterial suspension was prepared from the strain, inoculated to different phosphate-dissolving and potassium-dissolving mediums, and shaked for cultivation at 28° C. and 160 r.Math.min.sup.−1 for 5 days.

[0036] The formula of the phosphate-dissolving medium is the same as the embodiment 1, which only removes the agar; determining the soluble phosphorus content in each culture solution by a Mo—Sb Anti-Spectrophotometry Method.

[0037] The formula of the potassium-dissolving solid medium is as follows: Na.sub.2HPO.sub.4 2.0 g, MgSO.sub.4.7H.sub.2O 0.5 g, FeCl.sub.3 0.005 g, CaCO.sub.3 0.1 g, potassium feldspar 1.0 g, glucose 5.0 g, and distilled water 1000 mL, pH 7.0-7.5. Shaking cultivation was performed at 28° C. and 160 r.Math.min.sup.−1 for 5 days. 4 mL of H.sub.2O.sub.2 were added to each bottle of the bacterial solution, which was digested at 121° C. for 30 min and then centrifuged at 6000 r.Math.min.sup.−1 for 5 min, supernatant was took to make up to 100 mL, and the content of readily available potassium in the supernatant was determined by adopting a flame photometer.

[0038] Compared with the phosphorus-dissolving and potassium-dissolving abilities of various strains, the DW1 strain has stronger phosphorus-dissolving and potassium-dissolving abilities and better dissolving abilities on insoluble phosphorus and insoluble potassium.

[0039] IAA production ability of the selected DW1 strain was determined. The DW1 strain was inoculated into a nitrogen-containing liquid medium for shaking cultivation at 28° C. and 160 r.Math.min.sup.−1 for 5 days, centrifuged to remove precipitation, supernatant was collected, corresponding Sackowski's chromogenic reagent was added to the supernatant according to a ratio of 1:2, mixed and reacted at 25° C. in dark for 30 min. A nitrogen-containing liquid medium without strain inoculation was used as a blank control, absorbance at 530 nm was determined and thus, calculated IAA production level of the DW1 strain was calculated.

[0040] Sackowski's chromogenic reagent: 1 mL of 0.5 mol.Math.L.sup.−1FeCl.sub.3 solution is added to 50 mL of 35% HClO.sub.4 solution and mixed evenly. The formula of the nitrogen-containing liquid medium is as follows: sucrose 10.0 g, K.sub.2HPO.sub.4 2.0 g, MgSO.sub.4.7H.sub.2O 0.5 g, NaCl 0.1 g, yeast extract 0.5 g, CaCO.sub.3 0.5 g, agar 20 g, distilled water 400 mL, pH 7.0.

[0041] The phosphorus-dissolving and potassium-dissolving abilities and the IAA production ability of the DW1 strain are shown in Table 1. As can be seen from Table 1, the DW1 strain has a strong dissolving ability to insoluble phosphorus and insoluble potassium and has a high IAA production ability, indicating that the DW1 strain has the potential of promoting plant growth.

TABLE-US-00001 TABLE 1 The phosphorus-dissolving and potassium-dissolving abilities and the IAA production ability of the DW1 strain Phosphorus- Potassium- IAA production dissolving ability dissolving ability ability Strain (mg .Math. L.sup.−1) (mg .Math. L.sup.−1) (mg .Math. L.sup.−1) DW1 156.23 ± 9.36 10.73 ± 1.54 80.50 ± 3.01

Embodiment 3

[0042] Identification of Strains

[0043] A strain specie of the DW1 strain was identified by combining morphological observation, physiological and biochemical tests, and 16SrRNA gene sequence alignment analysis.

[0044] Physiological and biochemical characteristics of the DW1 strain were detected according to “Common Bacterial System Appraisal Manual” and “Berje's Bacterial Appraisal Manual”. The morphological test comprises gram staining; the physiological and biochemical tests comprise starch hydrolysis test, catalase test, VP test, methyl red (M-R) test, gelatin liquefaction test, glucose oxidation-fermentation test, and H.sub.2S production test, the results are shown in Table 2.

[0045] The 16SrRNA gene sequence of the DW1 strain was submitted to the NCBI database for BLAST comparison, the DW1 strain is determined to belong to the Bacillus sp. according to the results of the physiological and biochemical tests, and the 16SrRNA gene sequence of the DW1 strain is shown in SEQ ID NO. 1 listed in the Sequence List file.

TABLE-US-00002 TABLE 2 Some physiological and biochemical characteristics of the DW1 strain Glucose Starch Gelatin oxidation- H.sub.2S Gram Strain hydrolysis Catalase VP M-R liquefaction fermentation production staining DW1 + + + — + oxidatio — +

Embodiment 4

[0046] Preparation of the DW1 Growth-Promoting Bacterial Agent and use Thereof in Field Tests of Soybeans

[0047] 1. Preparation of Bacterial Agent

[0048] The strain on the LB slop medium was washed with 5 mL of physiological saline, the DW1 strain was inoculated into the LB liquid medium with a volume ratio of 2% for shaking cultivation at 28° C., 160 r.Math.min.sup.−1 for 24 h to prepare the DW1 liquid bacterial agent. When in use, the bacterial agent was diluted to OD.sub.680=0.8 by water.

[0049] 2. Field Tests of the Bacterial Agent

[0050] The test is divided into two groups, one group is an experimental group applied with the DW1 bacterial agent and the other group is a control group without a bacterial agent. There are 10 repetitions in each group. Soybean seeds were sowed in the field, and 20 mL of diluted bacterial agent were inoculated to the roots after the soybean seedlings emerge. After the soybeans are mature, the plant height, the node number, the effective branch number, the number of seeds per plant, the weight of beans per plant, and the weight of 100 seeds, the nitrogen content of soybean leaves, the phosphorus content of soybean leaves, the potassium content of soybean leaves, the soil ammonium nitrogen content, the soil effective phosphorus content and the soil readily available potassium content of the experimental group and the control group were determined. The results are shown in FIG. 1, Table 3, Table 4, and Table 5.

TABLE-US-00003 TABLE 3 The effect of the DW1 bacterial agent on the growth of soybeans in the field tests Plant height Node Effective branch Treatment cm number number Control group 43.32 ± 5.07 11.81 ± 1.28 4.90 ± 0.96  Experimental group 46.41 ± 3.39 12.83 ± 0.72 6.14 ± 0.59* Note: *indicates significant differences between treatments (p < 0.05).

[0051] As can be seen from Table 3, the effective branch number of the experimental group applied with the DW1 bacterial agent is improved by 25.31% compared with the control group without a bacterial agent and reached a significant level (p<0.05).

[0052] The influence of the DW1 bacterial agent on the soybean yield is shown in FIG. 1, and the number of seeds per plant, the weight of beans per plant, and the weight of 100 seeds of an experimental group applied with the DW1 bacterial agent are respectively improved by 50.82%, 57.83%, and 4.62% compared with a control group without a bacterial agent and reached extremely significant levels (p<0.01).

TABLE-US-00004 TABLE 4 The effect of the DW1 bacterial agent on the nutrient content of soybean leaves in the field tests Nitrogen content Phosphorus content Potassium content of the leaves of the leaves of the leaves Treatment g .Math. kg.sup.−1 g .Math. kg.sup.−1 g .Math. kg.sup.−1 Control group 3.99 ± 0.91  3.17 ± 0.09  10.56 ± 0.57  Experimental group 6.43 ± 1.08* 5.22 ± 0.48* 11.94 ± 0.27* Note: *indicates significant differences between treatments (p < 0.05).

[0053] As can be seen from Table 4, the nitrogen content, phosphorus content, and potassium content of the leaves of the soybean plants in the experimental group applied with the DW1 bacterial agent are respectively improved by 61.15%, 64.67%, and 13.07% compared with a control group without a bacterial agent, and all reached significant levels (p<0.05).

TABLE-US-00005 TABLE 5 The effect of the DW1 bacterial agent on soil nutrient content of soybean rhizosphere in the field tests Readily available Ammonium nitrogen Available phosphorus potassium content of soil content of soil content of soil Treatment mg .Math. kg.sup.−1 mg .Math. kg.sup.−1 mg .Math. kg.sup.−1 Control group 8.07 ± 0.24  24.68 ± 3.27  110.00 ± 8.00  Experimental group 12.79 ± 1.18** 32.50 ± 1.11* 138.00 ± 13.45* Note: *indicates significant differences between treatments (p < 0.05), **indicates extremely significant difference between treatments (p < 0.01).

[0054] As can be seen from Table 5, the ammonium nitrogen content, available phosphorus content, and readily available potassium content of rhizosphere soil in the treatment group applied with the DW1 bacterial agent are respectively improved by 58.49%, 31.69%, and 25.45% compared with a control group without a bacterial agent, the improved amount of the soil ammonium nitrogen reached an extremely significant level (p<0.01), and the improved amount of soil available phosphorus and soil readily available potassium reached a significant level (p<0.05). The DW1 bacterial agent can improve the content of ammonium nitrogen, available phosphorus, and readily available potassium in the soybean rhizosphere soil.

[0055] Test group 1 is applied with the DW1 bacterial agent, test group 2 is applied with an FK19 bacterial agent, the control group is applied without a bacterial agent, and there are 10 repetitions in each group. Soybean seeds were sowed in the field, and 20 mL of diluted DW1 bacterial agent and diluted FK19 bacterial agent were inoculated respectively to the roots after the soybean seedlings emerge. The oil content and protein content of the experimental group and the control group were determined; the results are shown in FIG. 2.

[0056] The FK19 bacterial agent is prepared from bacillus FK19 and has the same growth-promoting effect on soybean, and Chinese invention patent CN 109652340B describes the growth-promoting function of the FK19 bacterial agent on soybean. As can be seen from FIG. 2, the oil content of the soybeans applied with the DW1 bacterial agent is improved by 5.23% compared with the control without the bacterial agent and reached an extremely significant level (p<0.01), and the content of the soybean protein is not reduced. Compared with the control group, the FK19 bacterial agent, which also has the soybean growth-promoting effect, does not show the ability to improve the oil content of soybean. It shows that the DW1 bacterial agent in the present disclosure can improve the oil content of soybean.

[0057] As can be seen from Tables 3, 4, 5, and FIGS. 1 and 2, the DW1 strain can release insoluble phosphorus and insoluble potassium in the soil, improve the soil soluble nutrient content to promote the absorption of nutrients by soybeans, and improve the nutrient content of soybean leaves, further promote the growth of soybeans, and improve soybean yield and the oil content of the soybean.

[0058] It should be emphasized that the growth-promoting bacterial agent provided by the present disclosure can be combined with other bacteria agents or products with growth-promoting effects; although the growth-promoting bacterial agent of the present disclosure uses soybean as the experimental object, the implementation of the growth-promoting bacterial agent containing the DW1 strain on other plants should be regarded as an embodiment of the present disclosure.

[0059] The above description is only the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or equivalently replace some of the technical features. In the spirit and principles of the present disclosure, any modification, equivalent replacement, and improvement of the present disclosure shall be included in the protection scope of the present disclosure.